Version 0.3.0

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.gitea/scripts/release.py

@@ -0,0 +1,153 @@
+"""Publish the renderer's programs. Run by ci.yml.
+
+    release.py version         print version and channel
+    release.py publish <dir>   publish the programs in dir: a release for a vX.Y.Z tag, else the rolling nightly
+
+A vX.Y.Z tag is release X.Y.Z. Other builds are nightlies, "X.Y.Z-nightly.N+commit": N commits after the last
+release tag (0.0.0 before the first). The nightly pre-release (tag `nightly`) is replaced on every push to main.
+The same scheme as T5DE's own releases (t5de's .gitea/scripts/release.py).
+"""
+
+import hashlib
+import json
+import os
+import re
+import subprocess
+import sys
+import urllib.error
+import urllib.request
+import uuid
+from pathlib import Path
+
+ASSETS = ("t5deRenderEngine.dll", "t5de-renderer.exe")
+NIGHTLY_TAG = "nightly"
+USER_AGENT = "t5de-release (https://git.t5de.dev/t5de/t5de-renderer, 1)"
+RELEASE_TAG = re.compile(r"v(\d+)\.(\d+)\.(\d+)")
+
+
+def git(*args: str) -> str:
+    return subprocess.run(["git", *args], capture_output=True, text=True, check=True).stdout.strip()
+
+
+def version() -> dict[str, str]:
+    ref_name = os.environ.get("GITHUB_REF_NAME", "")
+    if os.environ.get("GITHUB_REF_TYPE") == "tag" and RELEASE_TAG.fullmatch(ref_name):
+        return {"version": ref_name[1:], "channel": "release", "tag": ref_name}
+    try:
+        last = git("describe", "--tags", "--abbrev=0", "--match", "v[0-9]*.[0-9]*.[0-9]*")
+        count = int(git("rev-list", "--count", f"{last}..HEAD"))
+        base = last[1:]
+    except subprocess.CalledProcessError:  # no release yet
+        count, base = int(git("rev-list", "--count", "HEAD")), "0.0.0"
+    commit = git("rev-parse", "--short=7", "HEAD")
+    return {"version": f"{base}-nightly.{count}+{commit}", "channel": "nightly", "tag": NIGHTLY_TAG}
+
+
+class Gitea:
+    def __init__(self):
+        self.api = f"{os.environ['GITHUB_SERVER_URL']}/api/v1/repos/{os.environ['GITHUB_REPOSITORY']}"
+        self.token = os.environ["GITEA_TOKEN"]
+
+    def request(self, method: str, path: str, body: dict | None = None, data: bytes | None = None,
+                content_type: str = "application/json"):
+        if body is not None:
+            data = json.dumps(body).encode()
+        req = urllib.request.Request(self.api + path, method=method, data=data,
+                                     # Cloudflare in front of the server refuses Python's default User-Agent.
+                                     headers={"Authorization": f"token {self.token}", "Content-Type": content_type,
+                                              "User-Agent": USER_AGENT})
+        try:
+            with urllib.request.urlopen(req, timeout=120) as response:
+                text = response.read()
+                return json.loads(text) if text else None
+        except urllib.error.HTTPError as e:
+            if e.code == 404 and method in ("GET", "DELETE"):
+                return None
+            raise SystemExit(f"{method} {path}: {e.code} {e.read().decode(errors='replace')}")
+
+    def upload(self, release_id: int, name: str, content: bytes):
+        boundary = uuid.uuid4().hex
+        data = (f"--{boundary}\r\nContent-Disposition: form-data; name=\"attachment\"; filename=\"{name}\"\r\n"
+                f"Content-Type: application/octet-stream\r\n\r\n").encode() + content + f"\r\n--{boundary}--\r\n".encode()
+        return self.request("POST", f"/releases/{release_id}/assets?name={name}", data=data,
+                            content_type=f"multipart/form-data; boundary={boundary}")
+
+
+def notes(info: dict[str, str], files: dict[str, bytes]) -> str:
+    nightly = ("A nightly build of the latest commit, for testing; it's replaced by the next one.\n\n"
+               if info["channel"] == "nightly" else "")
+    hashes = "\n".join(f"`{name}` sha256: `{hashlib.sha256(content).hexdigest()}`" for name, content in files.items())
+    return f"""{nightly}T5DE's renderer for IMVU Classic. T5DE's setup installs a pinned release with its T5DE Renderer
+patch, used when the client's Settings > Advanced > Graphics is OpenGL. To try this build instead, copy both files
+into a T5DE install's folder (with that patch).
+
+Unofficial: not made by or affiliated with IMVU. Use at your own risk.
+
+Version {info['version']} · commit {os.environ.get('GITHUB_SHA', git('rev-parse', 'HEAD'))}
+{hashes}
+"""
+
+
+def publish(folder: str):
+    info = version()
+    files = {name: (Path(folder) / name).read_bytes() for name in ASSETS}
+    gitea = Gitea()
+    previous = None
+    if info["channel"] == "nightly":
+        old = gitea.request("GET", f"/releases/tags/{NIGHTLY_TAG}")
+        if old:
+            previous = old["target_commitish"]
+            gitea.request("DELETE", f"/releases/{old['id']}")
+        gitea.request("DELETE", f"/tags/{NIGHTLY_TAG}")
+        release = gitea.request("POST", "/releases", {
+            "tag_name": NIGHTLY_TAG, "target_commitish": os.environ["GITHUB_SHA"],
+            "name": f"Nightly {info['version']}", "body": notes(info, files), "prerelease": True})
+    else:
+        release = gitea.request("GET", f"/releases/tags/{info['tag']}")
+        fields = {"name": f"T5DE Renderer {info['version']}", "body": notes(info, files), "prerelease": False}
+        if release:  # a rerun: refresh it
+            release = gitea.request("PATCH", f"/releases/{release['id']}", fields)
+            for asset in release.get("assets") or []:
+                if asset["name"] in files:
+                    gitea.request("DELETE", f"/releases/{release['id']}/assets/{asset['id']}")
+        else:
+            release = gitea.request("POST", "/releases", {"tag_name": info["tag"], **fields})
+    for name, content in files.items():
+        gitea.upload(release["id"], name, content)
+    print(f"Published {release['html_url']}")
+    if info["channel"] == "nightly" and os.environ.get("DISCORD_NIGHTLY_WEBHOOK"):
+        announce(os.environ["DISCORD_NIGHTLY_WEBHOOK"], info, release, previous)
+
+
+def announce(webhook: str, info: dict[str, str], release: dict, previous: str | None):
+    """Post the release to a Discord channel. Failing to doesn't fail the release."""
+    commits = []
+    if previous:
+        try:
+            commits = git("log", "--format=%h %s", "--no-merges", f"{previous}..HEAD").splitlines()
+        except subprocess.CalledProcessError:  # the previous nightly's commit is gone (history rewritten)
+            pass
+    shown = commits[:10] + ([f"and {len(commits) - 10} more"] if len(commits) > 10 else [])
+    description = f"[Download]({release['html_url']})"
+    if shown:
+        description += "\n\n" + "\n".join(f"• {line}" for line in shown)
+    body = {"embeds": [{"title": f"Renderer Nightly {info['version']}", "url": release["html_url"],
+                        "description": description[:4000], "color": 0xFFD200}]}
+    req = urllib.request.Request(webhook, method="POST", data=json.dumps(body).encode(),
+                                 headers={"Content-Type": "application/json",
+                                          "User-Agent": USER_AGENT})
+    try:
+        urllib.request.urlopen(req, timeout=30).close()
+        print("Announced on Discord")
+    except (urllib.error.URLError, TimeoutError) as e:
+        print(f"warning: couldn't post to Discord: {e}")
+
+
+if __name__ == "__main__":
+    if sys.argv[1:] == ["version"]:
+        for key, value in version().items():
+            print(f"{key}={value}")
+    elif len(sys.argv) == 3 and sys.argv[1] == "publish":
+        publish(sys.argv[2])
+    else:
+        raise SystemExit(__doc__)

.gitea/workflows/ci.yml

@@ -0,0 +1,59 @@
+# Builds the adapter (32-bit) and the renderer process (64-bit), runs the tests, and publishes both programs: pushes to
+# main replace the nightly pre-release, vX.Y.Z tags make release X.Y.Z (.gitea/scripts/release.py).
+#
+# Runs on T5DE's Windows runner (label `windows`, jobs run directly on the machine: it needs Visual Studio's
+# compiler). The checkout lives in a fixed folder there ($T5DE_BUILD_ROOT, set in the runner's config), so Diligent
+# Engine is fetched and built once, not on every run. Never on pull requests: their code would run on that machine.
+name: CI
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: windows
+    defaults:
+      run:
+        # Steps run as script files, which Windows' default execution policy refuses.
+        shell: powershell -NoProfile -ExecutionPolicy Bypass -Command ". '{0}'"
+    steps:
+      - name: Check out
+        env:
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          function git { & git.exe -c "http.extraHeader=Authorization: token $env:TOKEN" @args; if ($LASTEXITCODE) { exit $LASTEXITCODE } }
+          $root = if ($env:T5DE_BUILD_ROOT) { $env:T5DE_BUILD_ROOT } else { $env:GITHUB_WORKSPACE }
+          $src = Join-Path $root ($env:GITHUB_REPOSITORY -replace '/', '-')
+          if (-not (Test-Path (Join-Path $src .git))) { git init -q $src }
+          Set-Location $src
+          git fetch -q --force --tags "$env:GITHUB_SERVER_URL/$env:GITHUB_REPOSITORY" "+${env:GITHUB_REF}:refs/remotes/ci/head"
+          git checkout -q --force --detach $env:GITHUB_SHA
+          git clean -q -ffdx -e /build/
+          "T5DE_SRC=$src" | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+
+      - name: Build and test the adapter
+        working-directory: ${{ env.T5DE_SRC }}
+        run: cmake --workflow --preset adapter
+
+      - name: Build the renderer process
+        working-directory: ${{ env.T5DE_SRC }}
+        run: cmake --workflow --preset renderer
+
+      - name: Collect the programs
+        working-directory: ${{ env.T5DE_SRC }}
+        run: |
+          cmake --install build/windows-x86 --config Release --prefix dist
+          if ($LASTEXITCODE) { exit $LASTEXITCODE }
+          cmake --install build/windows-x64 --config Release --prefix dist
+
+      - name: Publish the release
+        if: github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v')
+        working-directory: ${{ env.T5DE_SRC }}
+        env:
+          GITEA_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          # Optional: a Discord webhook URL that nightlies are announced on.
+          DISCORD_NIGHTLY_WEBHOOK: ${{ secrets.DISCORD_NIGHTLY_WEBHOOK }}
+        run: python .gitea/scripts/release.py publish dist

CLAUDE.md

@@ -1,7 +1,9 @@
 # t5de-renderer
 
-A renderer plugin for IMVU Classic (see README.md and docs/interface.md). Part of T5DE; the patches and the patcher
-are in the `t5de` repository (git.t5de.dev/t5de/t5de, usually checked out beside this one).
+A new renderer for IMVU Classic: a 32-bit adapter DLL the client loads as a renderer plugin, and a 64-bit renderer
+process drawing with Diligent Engine (see README.md, docs/architecture.md, docs/interface.md). Part of T5DE; the
+patches and the patcher are in the `t5de` repository (git.t5de.dev/t5de/t5de, usually checked out beside this one).
+The user chose this architecture for ray tracing, mesh shaders and a possible browser client later.
 
 ## Rules
 
@@ -13,9 +15,12 @@ are in the `t5de` repository (git.t5de.dev/t5de/t5de, usually checked out beside
 
 ## Notes
 
-- The plugin must match IMVU's ABI: 32-bit, MSVC (cl or clang-cl; MinGW's C++ ABI differs), `__thiscall`
-  virtual methods in IMVU's vtable order, Boost 1.61's `shared_ptr` layout. Exceptions must not cross into IMVU's
-  code (a different C runtime); the CRT is linked statically.
+- The adapter must match IMVU's ABI: 32-bit, MSVC (cl or clang-cl; MinGW's C++ ABI differs), `__thiscall`
+  virtual methods in IMVU's vtable order (never overloaded: MSVC orders overloads unlike their declaration), Boost
+  1.61's `shared_ptr` layout. Exceptions must not cross into IMVU's code (a different C runtime); the CRT is linked
+  statically. Code shared with the 64-bit renderer process (`include/t5de/protocol/`) uses fixed-size fields only.
+- The development VM has no graphics driver (Microsoft Basic Render Driver): Direct3D 11 works in software, IMVU's
+  OpenGL renderer doesn't, and performance there means nothing.
 - Ghidra 12.2 (Java 25) is at `%LOCALAPPDATA%\Programs\ghidra_12.2_PUBLIC`; projects in
   `%LOCALAPPDATA%\t5de-dev\ghidra`, analysed headless (`support\analyzeHeadless.bat`). The client to analyse is the
   `t5de` checkout's `.cache/<version>/install`.

CMakeLists.txt

@@ -1,19 +1,22 @@
 cmake_minimum_required(VERSION 3.28)
 
 project(t5de-renderer
-    VERSION 0.1.0
+    VERSION 0.3.0
     DESCRIPTION "A new 3D renderer for the IMVU Classic client"
     LANGUAGES CXX)
 
-# The plugin is loaded into IMVU Classic, a 32-bit program built with Visual C++: it must use the same ABI.
+# Two programs, for two architectures (a preset for each, see CMakePresets.json):
+# - 32-bit: the adapter, t5deRenderEngine.dll, a renderer plugin loaded into IMVU Classic (a 32-bit Visual C++
+#   program, so it must match its ABI).
+# - 64-bit: the renderer process, t5de-renderer.exe, which draws.
 if(NOT MSVC) # cl or clang-cl
-    message(FATAL_ERROR "Build with MSVC or clang-cl: the plugin must match IMVU Classic's Visual C++ ABI.")
-endif()
-if(NOT CMAKE_SIZEOF_VOID_P EQUAL 4)
-    message(FATAL_ERROR "Build for 32-bit x86 (IMVU Classic is 32-bit): use a CMakePresets.json preset.")
+    message(FATAL_ERROR "Build with MSVC or clang-cl: the adapter must match IMVU Classic's Visual C++ ABI.")
 endif()
 
-# The C runtime is linked statically, so the plugin needs nothing installed beside it.
+# No C++ modules: skip scanning for them.
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
+# The C runtime is linked statically, so the programs need nothing installed beside them.
 set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 
 # Warnings and conformance for our own targets.
@@ -23,25 +26,25 @@ target_compile_features(t5de_options INTERFACE cxx_std_20)
 target_compile_options(t5de_options INTERFACE /W4 /permissive- /utf-8 /Zc:__cplusplus)
 target_compile_definitions(t5de_options INTERFACE WIN32_LEAN_AND_MEAN NOMINMAX UNICODE _UNICODE)
 
-# Our declarations of IMVU's interfaces.
-add_library(t5de_imvu INTERFACE)
-add_library(t5de::imvu ALIAS t5de_imvu)
-target_include_directories(t5de_imvu INTERFACE
-    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)
-target_compile_features(t5de_imvu INTERFACE cxx_std_20)
-
-# The renderer plugin, t5deRenderEngine.dll.
-add_library(t5de_render_engine SHARED
-    src/log.cpp
-    src/passthrough_engine.cpp
-    src/plugin.cpp
-    src/plugin.def)
-set_target_properties(t5de_render_engine PROPERTIES OUTPUT_NAME t5deRenderEngine)
-target_link_libraries(t5de_render_engine PRIVATE t5de::imvu t5de::options)
-
-install(TARGETS t5de_render_engine RUNTIME DESTINATION .)
+# What the adapter and the renderer process share.
+add_library(t5de_protocol INTERFACE)
+add_library(t5de::protocol ALIAS t5de_protocol)
+target_include_directories(t5de_protocol INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)
+target_compile_features(t5de_protocol INTERFACE cxx_std_20)
 
 include(CTest)
+
+if(CMAKE_SIZEOF_VOID_P EQUAL 4)
+    # Our declarations of IMVU's interfaces (32-bit layouts).
+    add_library(t5de_imvu INTERFACE)
+    add_library(t5de::imvu ALIAS t5de_imvu)
+    target_include_directories(t5de_imvu INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)
+    target_compile_features(t5de_imvu INTERFACE cxx_std_20)
+
+    add_subdirectory(adapter)
     if(BUILD_TESTING)
         add_subdirectory(tests)
     endif()
+else()
+    add_subdirectory(renderer)
+endif()

CMakePresets.json

@@ -3,29 +3,43 @@
   "cmakeMinimumRequired": { "major": 3, "minor": 28, "patch": 0 },
   "configurePresets": [
     {
-      "name": "windows-x86",
-      "displayName": "Windows, 32-bit (Visual Studio Build Tools)",
-      "description": "IMVU Classic is a 32-bit Visual C++ program: build for Win32 with MSVC.",
+      "name": "windows",
+      "hidden": true,
       "generator": "Visual Studio 18 2026",
-      "architecture": { "value": "Win32", "strategy": "set" },
       "binaryDir": "${sourceDir}/build/${presetName}",
-      "installDir": "${sourceDir}/build/${presetName}/install",
+      "installDir": "${sourceDir}/build/install",
       "condition": { "type": "equals", "lhs": "${hostSystemName}", "rhs": "Windows" }
+    },
+    {
+      "name": "windows-x86",
+      "inherits": "windows",
+      "displayName": "Adapter (32-bit)",
+      "description": "t5deRenderEngine.dll, loaded into IMVU Classic, a 32-bit Visual C++ program.",
+      "architecture": { "value": "Win32", "strategy": "set" }
+    },
+    {
+      "name": "windows-x64",
+      "inherits": "windows",
+      "displayName": "Renderer process (64-bit)",
+      "description": "t5de-renderer.exe, with Diligent Engine (fetched and built on the first configure).",
+      "architecture": { "value": "x64", "strategy": "set" }
     }
   ],
   "buildPresets": [
-    { "name": "debug", "configurePreset": "windows-x86", "configuration": "Debug" },
-    { "name": "release", "configurePreset": "windows-x86", "configuration": "Release" }
+    { "name": "adapter-debug", "configurePreset": "windows-x86", "configuration": "Debug" },
+    { "name": "adapter-release", "configurePreset": "windows-x86", "configuration": "Release" },
+    { "name": "renderer-debug", "configurePreset": "windows-x64", "configuration": "Debug" },
+    { "name": "renderer-release", "configurePreset": "windows-x64", "configuration": "Release" }
   ],
   "testPresets": [
     {
-      "name": "debug",
+      "name": "adapter-debug",
       "configurePreset": "windows-x86",
       "configuration": "Debug",
       "output": { "outputOnFailure": true }
     },
     {
-      "name": "release",
+      "name": "adapter-release",
       "configurePreset": "windows-x86",
       "configuration": "Release",
       "output": { "outputOnFailure": true }
@@ -33,11 +47,18 @@
   ],
   "workflowPresets": [
     {
-      "name": "release",
+      "name": "adapter",
       "steps": [
         { "type": "configure", "name": "windows-x86" },
-        { "type": "build", "name": "release" },
-        { "type": "test", "name": "release" }
+        { "type": "build", "name": "adapter-release" },
+        { "type": "test", "name": "adapter-release" }
+      ]
+    },
+    {
+      "name": "renderer",
+      "steps": [
+        { "type": "configure", "name": "windows-x64" },
+        { "type": "build", "name": "renderer-release" }
       ]
     }
   ]

README.md

@@ -1,25 +1,28 @@
 # t5de-renderer
 
-A new 3D renderer for the IMVU Classic client, as a renderer plugin the client loads like its own OpenGL renderer.
-Part of [T5DE](https://git.t5de.dev/t5de/t5de); unofficial, not affiliated with IMVU.
+A new 3D renderer for the IMVU Classic client. Part of [T5DE](https://git.t5de.dev/t5de/t5de); unofficial, not
+affiliated with IMVU.
 
-For now it's a pass-through: it wraps IMVU's Direct3D renderer and logs what each frame draws, to prove our
-declarations of IMVU's interface (`docs/interface.md`).
+Two programs (`docs/architecture.md`): an adapter, `t5deRenderEngine.dll`, which IMVU Classic loads as a renderer
+plugin, and a 64-bit renderer process, `t5de-renderer.exe`, which draws with
+[Diligent Engine](https://github.com/DiligentGraphics/DiligentCore). For now the client's own Direct3D renderer still
+draws the scene, and the renderer process proves the setup by drawing a small box over it. `docs/interface.md` has
+what we know of IMVU's renderer interface.
 
 ## Building
 
-Needs Visual Studio Build Tools 2026 (the C++ workload) and CMake 3.28 or newer. IMVU Classic is a 32-bit
-Visual C++ program, so the plugin is built for 32-bit Windows (the `windows-x86` preset):
+Needs Visual Studio Build Tools 2026 (the C++ workload) and CMake 3.28 or newer. One preset per program:
 
 ```sh
-cmake --workflow --preset release
+cmake --workflow --preset adapter    # build/windows-x86/adapter/Release/t5deRenderEngine.dll, and the tests
+cmake --workflow --preset renderer   # build/windows-x64/renderer/Release/t5de-renderer.exe
 ```
 
-That configures, builds `build/windows-x86/Release/t5deRenderEngine.dll` and runs the tests. Or step by step:
-`cmake --preset windows-x86`, `cmake --build --preset debug`, `ctest --preset debug`.
+The renderer's first configure fetches Diligent Engine (pinned in `renderer/CMakeLists.txt`) and builds it, which
+takes a while.
 
 ## Trying it
 
-Copy `t5deRenderEngine.dll` into a T5DE client folder built with the `t5de-renderer` patch, which has the OpenGL
-setting load it in place of `glRenderEngine.dll`, then choose OpenGL in Settings > Advanced. The log is
+Copy both programs into a T5DE client folder built with the `t5de-renderer` patch, which has the OpenGL setting load
+the adapter in place of `glRenderEngine.dll`, then choose OpenGL in Settings > Advanced. The adapter's log is
 `%TEMP%\t5de-renderer.log`.

adapter/CMakeLists.txt

@@ -0,0 +1,17 @@
+# t5deRenderEngine.dll, the adapter: a renderer plugin for IMVU Classic (32-bit).
+
+add_library(t5de_render_engine SHARED
+    engine.cpp
+    frame_pacer.cpp
+    log.cpp
+    pixmap.cpp
+    plugin.cpp
+    plugin.def
+    recorder.cpp
+    renderer_process.cpp
+    resources.cpp
+    scene_hooks.cpp)
+set_target_properties(t5de_render_engine PROPERTIES OUTPUT_NAME t5deRenderEngine)
+target_link_libraries(t5de_render_engine PRIVATE t5de::imvu t5de::protocol t5de::options)
+
+install(TARGETS t5de_render_engine RUNTIME DESTINATION .)

adapter/engine.cpp

@@ -0,0 +1,448 @@
+#include "engine.hpp"
+
+#include <windows.h>
+
+#include <algorithm>
+#include <bit>
+#include <cmath>
+#include <cstring>
+#include <vector>
+
+#include "frame_pacer.hpp"
+#include "inner_timing.hpp"
+#include "log.hpp"
+#include "resources.hpp"
+
+namespace t5de {
+
+using protocol::Op;
+using protocol::State;
+
+namespace {
+
+protocol::SetTransform transform_command(const imvu::Transform& t)
+{
+    protocol::SetTransform command{};
+    std::memcpy(command.m, &t.linear[0][0], sizeof(float) * 9);
+    command.m[9] = t.translation.x;
+    command.m[10] = t.translation.y;
+    command.m[11] = t.translation.z;
+    return command;
+}
+
+} // namespace
+
+Engine::Engine(imvu::SharedPtr<imvu::PiRenderEngine> inner, std::shared_ptr<Recorder> recorder, HWND window)
+    : inner_(std::move(inner)), recorder_(std::move(recorder)), window_(window), innerTicksAtStats_(innerTicks)
+{
+    QueryPerformanceCounter(&statsStart_);
+    if (window_ != nullptr) {
+        frame_pacer::add(window_);
+    }
+}
+
+Engine::~Engine()
+{
+    if (window_ != nullptr) {
+        frame_pacer::remove(window_);
+    }
+    log::info("engine: destroyed after {} frames", frames_);
+}
+
+void Engine::setState(State state, std::uint32_t value)
+{
+    recorder_->add(Op::SetState, protocol::SetState{state, value});
+}
+
+void Engine::resizeFrameBuffer(imvu::Vec2i size) { const InnerCall timed; inner_->resizeFrameBuffer(size); }
+
+void Engine::enable2dFrameBuffer() { const InnerCall timed; inner_->enable2dFrameBuffer(); }
+
+void Engine::clear(std::uint32_t flags, imvu::Color color)
+{
+    if (innerDraws()) {
+        { const InnerCall timed; inner_->clear(flags, color); }
+    }
+    recorder_->add(Op::Clear, protocol::Clear{flags, color});
+}
+
+void Engine::setProjection(imvu::Vec2i viewport, const imvu::Mat4f& projection)
+{
+    { const InnerCall timed; inner_->setProjection(viewport, projection); }
+    if (projection.m[2][3] == 0.0f) {
+        ++stats_.flat;
+    }
+    protocol::SetProjection command{viewport.x, viewport.y, {}};
+    std::memcpy(command.m, &projection.m[0][0], sizeof(command.m));
+    recorder_->add(Op::SetProjection, command);
+}
+
+void Engine::setModelSpace(const imvu::Transform& model)
+{
+    { const InnerCall timed; inner_->setModelSpace(model); }
+    recorder_->add(Op::SetModel, transform_command(model));
+}
+
+void Engine::setViewSpace(const imvu::Transform& view)
+{
+    { const InnerCall timed; inner_->setViewSpace(view); }
+    recorder_->add(Op::SetView, transform_command(view));
+}
+
+void Engine::setTextures(imvu::PiRenderTexture* texture0, imvu::PiRenderTexture* texture1)
+{
+    { const InnerCall timed; inner_->setTextures(inner(texture0), inner(texture1)); }
+    for (imvu::PiRenderTexture* texture : {texture0, texture1}) {
+        if (texture != nullptr && id(texture) == 0 && foreignLogged_ < 20) {
+            ++foreignLogged_;
+            log::info("engine: frame {}: a texture the client renderer made ({})", frames_, static_cast<void*>(texture));
+        }
+    }
+    recorder_->add(Op::SetTextures, protocol::SetTextures{id(texture0), id(texture1)});
+}
+
+void Engine::setDepthTestingOn(bool on)
+{
+    { const InnerCall timed; inner_->setDepthTestingOn(on); }
+    setState(State::DepthTest, on);
+}
+
+void Engine::setDepthWritingOn(bool on)
+{
+    { const InnerCall timed; inner_->setDepthWritingOn(on); }
+    setState(State::DepthWrite, on);
+}
+
+void Engine::setBlendMode(imvu::RenderBlendMode mode)
+{
+    { const InnerCall timed; inner_->setBlendMode(mode); }
+    setState(State::BlendMode, static_cast<std::uint32_t>(mode));
+}
+
+void Engine::setAlphaTestingOn(bool on)
+{
+    { const InnerCall timed; inner_->setAlphaTestingOn(on); }
+    setState(State::AlphaTest, on);
+}
+
+void Engine::setAlphaTestValue(float value)
+{
+    { const InnerCall timed; inner_->setAlphaTestValue(value); }
+    setState(State::AlphaReference, static_cast<std::uint32_t>(std::lround(value * 255.0f)));
+}
+
+void Engine::setBlendingOn(bool on)
+{
+    { const InnerCall timed; inner_->setBlendingOn(on); }
+    setState(State::Blending, on);
+}
+
+void Engine::setBackFaceCullingOn(bool on)
+{
+    { const InnerCall timed; inner_->setBackFaceCullingOn(on); }
+    setState(State::Culling, on);
+}
+
+void Engine::setNormalInvertingOn(bool on)
+{
+    { const InnerCall timed; inner_->setNormalInvertingOn(on); }
+    setState(State::NormalInverting, on);
+}
+
+void Engine::setLightingOn(bool on)
+{
+    { const InnerCall timed; inner_->setLightingOn(on); }
+    setState(State::Lighting, on);
+}
+
+void Engine::setLightProperties(std::uint32_t index, const imvu::LightProperties& light)
+{
+    { const InnerCall timed; inner_->setLightProperties(index, light); }
+    protocol::SetLight command{index, light.enabled, light.diffuse,
+                               light.type == imvu::LightType::Directional,
+                               {light.vector.x, light.vector.y, light.vector.z}};
+    // IMVU's Direct3D renderer shines a directional light along -vector, along -x for a zero vector.
+    if (command.directional && light.vector.x == 0 && light.vector.y == 0 && light.vector.z == 0) {
+        command.vector[0] = 1;
+    }
+    recorder_->add(Op::SetLight, command);
+}
+
+void Engine::setFogOn(bool on)
+{
+    { const InnerCall timed; inner_->setFogOn(on); }
+    setState(State::Fog, on);
+}
+
+void Engine::setFogAttributes(float start, float end, imvu::Color color)
+{
+    { const InnerCall timed; inner_->setFogAttributes(start, end, color); }
+    recorder_->add(Op::SetFog, protocol::SetFog{start, end, color});
+}
+
+void Engine::setTextureTransformMatrixIdentity(std::uint32_t stage)
+{
+    { const InnerCall timed; inner_->setTextureTransformMatrixIdentity(stage); }
+    recorder_->add(Op::SetTextureTransform, protocol::SetTextureTransform{stage, 1, {1, 0, 0, 1, 0, 0}});
+}
+
+void Engine::setTextureTransformMatrix(std::uint32_t stage, const imvu::TextureTransform& transform)
+{
+    { const InnerCall timed; inner_->setTextureTransformMatrix(stage, transform); }
+    protocol::SetTextureTransform command{stage, 0, {}};
+    std::memcpy(command.m, transform.m, sizeof(command.m));
+    recorder_->add(Op::SetTextureTransform, command);
+}
+
+void Engine::setEnvironmentAmbient(imvu::Color color)
+{
+    { const InnerCall timed; inner_->setEnvironmentAmbient(color); }
+    setState(State::Ambient, color);
+}
+
+imvu::PiRenderTexture* Engine::newRenderTexture(const imvu::Pixmap& pixmap, std::uint32_t flags)
+{
+    imvu::PiRenderTexture* texture = inner_->newRenderTexture(pixmap, flags);
+    if (texture == nullptr) {
+        return nullptr;
+    }
+    return new Texture(texture, recorder_, recorder_->createTexture(pixmap, flags));
+}
+
+imvu::PiInternalIndexBuffer* Engine::newIndexBuffer(std::uint32_t count, const std::uint16_t* indices)
+{
+    imvu::PiInternalIndexBuffer* buffer = inner_->newIndexBuffer(count, indices);
+    if (buffer == nullptr) {
+        return nullptr;
+    }
+    return new IndexBuffer(buffer, recorder_,
+                           recorder_->createBuffer(protocol::BufferKind::Index, indices, 2, 2, count));
+}
+
+imvu::PiInternalVertexBuffer* Engine::newStaticVertexBuffer(const void* data, std::uint32_t stride,
+                                                            std::uint32_t elementSize, std::uint32_t elementCount)
+{
+    imvu::PiInternalVertexBuffer* buffer = inner_->newStaticVertexBuffer(data, stride, elementSize, elementCount);
+    if (buffer == nullptr) {
+        return nullptr;
+    }
+    return new VertexBuffer(
+        buffer, recorder_,
+        recorder_->createBuffer(protocol::BufferKind::Vertex, data, stride, elementSize, elementCount));
+}
+
+imvu::PiInternalVertexBuffer* Engine::newDynamicVertexBuffer(std::uint32_t elementSize, std::uint32_t elementCount)
+{
+    imvu::PiInternalVertexBuffer* buffer = inner_->newDynamicVertexBuffer(elementSize, elementCount);
+    if (buffer == nullptr) {
+        return nullptr;
+    }
+    return new VertexBuffer(
+        buffer, recorder_,
+        recorder_->createBuffer(protocol::BufferKind::Vertex, nullptr, 0, elementSize, elementCount));
+}
+
+imvu::SharedPtr<imvu::PiPixmapRenderTarget> Engine::newPixmapRenderTarget(imvu::Vec2i size)
+{
+    log::info("engine: frame {}: a {}x{} pixmap render target", frames_, size.x, size.y);
+    if (!recorder_->active() || size.x <= 0 || size.y <= 0) {
+        return inner_->newPixmapRenderTarget(size);
+    }
+    return imvu::SharedPtr<PixmapTarget>(std::make_unique<PixmapTarget>(recorder_, size));
+}
+
+imvu::SharedPtr<imvu::PiTextureRenderTarget> Engine::newTextureRenderTarget(imvu::Vec2i size)
+{
+    log::info("engine: frame {}: a {}x{} texture render target", frames_, size.x, size.y);
+    if (!recorder_->active() || size.x <= 0 || size.y <= 0) {
+        return inner_->newTextureRenderTarget(size);
+    }
+    return imvu::SharedPtr<TextureTarget>(std::make_unique<TextureTarget>(recorder_, size));
+}
+
+void Engine::beginRendering(imvu::PiRenderTarget* target)
+{
+    QueryPerformanceCounter(&frameStart_);
+    windowFrame_ = target == nullptr;
+    if (windowFrame_) {
+        if (lastWindowFrame_ != 0) {
+            LARGE_INTEGER frequency;
+            QueryPerformanceFrequency(&frequency);
+            longestGap_ = std::max(longestGap_, static_cast<double>(frameStart_.QuadPart - lastWindowFrame_) /
+                                                    static_cast<double>(frequency.QuadPart));
+        }
+        lastWindowFrame_ = frameStart_.QuadPart;
+    }
+    // Frames into our render targets are drawn by the renderer process only; the client's renderer doesn't know them.
+    ourTarget_ = ours(target) ? target : nullptr;
+    // Decided per frame: frames into the client renderer's render targets, and frames while the renderer process
+    // doesn't cover the view, are drawn by the client's renderer.
+    const bool takenOver = ourTarget_ != nullptr || (target == nullptr && recorder_->covering());
+    // Frames the client's renderer doesn't draw aren't begun in it either: its endRendering presents, which can wait
+    // for the display (and would show nothing: the renderer process's window covers it).
+    innerFrame_ = !takenOver;
+    if (innerFrame_) {
+        { const InnerCall timed; inner_->beginRendering(target); }
+    }
+    if (takenOver != takenOver_ && target == nullptr) {
+        log::info("engine: frame {}: {}", frames_, takenOver ? "drawn by the renderer process" : "drawn by the client's renderer");
+    }
+    takenOver_ = takenOver;
+    if (target != nullptr && foreignLogged_ < 20) {
+        ++foreignLogged_;
+        log::info("engine: frame {}: drawing into {} render target ({})", frames_,
+                  ourTarget_ != nullptr ? "our" : "the client renderer's", static_cast<void*>(target));
+    }
+    protocol::BeginFrame begin{target == nullptr ? 0 : protocol::foreignTarget, 0};
+    if (const auto* pixmap = dynamic_cast<const PixmapTarget*>(ourTarget_)) {
+        begin = {pixmap->id(), 1};
+    } else if (const auto* texture = dynamic_cast<const TextureTarget*>(ourTarget_)) {
+        begin = {texture->id(), 0};
+    }
+    recorder_->add(Op::BeginFrame, begin);
+}
+
+void Engine::endRendering()
+{
+    if (innerFrame_) {
+        { const InnerCall timed; inner_->endRendering(); }
+    }
+    LARGE_INTEGER now;
+    QueryPerformanceCounter(&now);
+    recorder_->add(Op::EndFrame, protocol::EndFrame{static_cast<std::uint64_t>(now.QuadPart)});
+    recorder_->flush(true);
+    if (auto* pixmap = dynamic_cast<PixmapTarget*>(ourTarget_)) {
+        pixmap->setPixels(recorder_->readBack());
+    } else if (windowFrame_ && window_ != nullptr) {
+        LARGE_INTEGER end, frequency;
+        QueryPerformanceCounter(&end);
+        QueryPerformanceFrequency(&frequency);
+        const double seconds =
+            static_cast<double>(end.QuadPart - frameStart_.QuadPart) / static_cast<double>(frequency.QuadPart);
+        frameSeconds_ += seconds;
+        frame_pacer::frameDrawn(window_, seconds);
+    }
+    ourTarget_ = nullptr;
+    ++frames_;
+    if (frames_ % 300 == 0) {
+        LARGE_INTEGER ended, frequency;
+        QueryPerformanceCounter(&ended);
+        QueryPerformanceFrequency(&frequency);
+        const double seconds =
+            static_cast<double>(ended.QuadPart - statsStart_.QuadPart) / static_cast<double>(frequency.QuadPart);
+        statsStart_ = ended;
+        const Recorder::Counters sent = recorder_->takeCounters();
+        if (statsLogged_ < 6 || frames_ % 3000 == 0) {
+            ++statsLogged_;
+            log::info("engine: last 300 frames: {:.0f} per second, at most {:.1f} ms apart; each {:.2f} ms beginRendering to "
+                      "endRendering, {:.2f} ms in the client renderer's methods, {:.2f} ms sending, {:.0f} KB sent, {:.1f} "
+                      "buffer updates ({:.0f} KB); drawTriangles {} (and {} with buffers not ours), drawTrianglesFromMemory "
+                      "{} (and {} without indices), point sprites {}, lines {}, 2D projections {}",
+                      300 / seconds, longestGap_ * 1000, frameSeconds_ * 1000 / 300,
+                      static_cast<double>(innerTicks - innerTicksAtStats_) * 1000 / static_cast<double>(frequency.QuadPart) / 300,
+                      sent.sendSeconds * 1000 / 300,
+                      static_cast<double>(sent.bytes) / 1024 / 300, sent.bufferUpdates / 300.0,
+                      static_cast<double>(sent.bufferBytes) / 1024 / 300, stats_.triangles, stats_.foreignTriangles,
+                      stats_.indexed, stats_.unindexed, stats_.sprites, stats_.lines, stats_.flat);
+        }
+        stats_ = {};
+        frameSeconds_ = 0;
+        longestGap_ = 0;
+        innerTicksAtStats_ = innerTicks;
+    }
+}
+
+void Engine::drawTriangles(imvu::PiInternalIndexBuffer* indices, imvu::PiInternalVertexBuffer* positions,
+                           imvu::PiInternalVertexBuffer* normals, imvu::PiInternalVertexBuffer* texCoords,
+                           imvu::PiInternalVertexBuffer* colors)
+{
+    if (innerDraws()) {
+        { const InnerCall timed; inner_->drawTriangles(inner(indices), inner(positions), inner(normals), inner(texCoords), inner(colors)); }
+    }
+    ++(id(indices) != 0 && id(positions) != 0 ? stats_.triangles : stats_.foreignTriangles);
+    recorder_->add(Op::DrawTriangles,
+                   protocol::DrawTriangles{id(indices), id(positions), id(normals), id(texCoords), id(colors)});
+}
+
+void Engine::drawLine(imvu::Vec3f from, imvu::Vec3f to, imvu::Color color)
+{
+    if (innerDraws()) {
+        { const InnerCall timed; inner_->drawLine(from, to, color); }
+    }
+    ++stats_.lines;
+}
+
+void Engine::drawPointSprites(const imvu::PointSpriteVector& sprites)
+{
+    if (innerDraws()) {
+        { const InnerCall timed; inner_->drawPointSprites(sprites); }
+    }
+    ++stats_.sprites;
+    if (sprites.first == nullptr || sprites.last <= sprites.first) {
+        return;
+    }
+    const auto count = static_cast<std::uint32_t>(sprites.last - sprites.first);
+    if (std::byte* payload = recorder_->add(Op::DrawPointSprites, protocol::DrawPointSprites{count},
+                                            std::size_t{count} * sizeof(imvu::PointSprite))) {
+        std::memcpy(payload, sprites.first, std::size_t{count} * sizeof(imvu::PointSprite));
+    }
+}
+
+void Engine::drawTrianglesFromMemory(std::uint32_t vertexCount, std::uint32_t indexCount,
+                                     const std::uint16_t* indices,
+                                     const imvu::VertexAttributeArray<imvu::Vec3f>& positions,
+                                     const imvu::VertexAttributeArray<imvu::Vec3f>& normals,
+                                     const imvu::VertexAttributeArray<imvu::Vec2f>& texCoords,
+                                     const imvu::VertexAttributeArray<imvu::Color>& colors)
+{
+    if (innerDraws()) {
+        { const InnerCall timed; inner_->drawTrianglesFromMemory(vertexCount, indexCount, indices, positions, normals, texCoords, colors); }
+    }
+    ++(indices != nullptr ? stats_.indexed : stats_.unindexed);
+    if (positions.data == nullptr || vertexCount == 0) {
+        return;
+    }
+    // Without indices: the vertices in order, as a triangle list.
+    std::vector<std::uint16_t> sequence;
+    if (indices == nullptr) {
+        if (vertexCount > 0xffff) {
+            return;
+        }
+        sequence.resize(vertexCount - vertexCount % 3);
+        for (std::size_t i = 0; i < sequence.size(); ++i) {
+            sequence[i] = static_cast<std::uint16_t>(i);
+        }
+        indices = sequence.data();
+        indexCount = static_cast<std::uint32_t>(sequence.size());
+    }
+    const bool hasNormals = normals.data != nullptr && normals.count >= vertexCount;
+    const bool hasTexCoords = texCoords.data != nullptr && texCoords.count >= vertexCount;
+    const bool hasColors = colors.data != nullptr && colors.count >= vertexCount;
+    const std::size_t indexBytes = protocol::padded(std::size_t{indexCount} * 2);
+    const std::size_t size = indexBytes + std::size_t{vertexCount} * (12 + (hasNormals ? 12 : 0) +
+                                                                      (hasTexCoords ? 8 : 0) + (hasColors ? 4 : 0));
+    std::byte* payload = recorder_->add(Op::DrawArrays,
+                                        protocol::DrawArrays{vertexCount, indexCount, hasNormals, hasTexCoords,
+                                                             hasColors},
+                                        size);
+    if (payload == nullptr) {
+        return;
+    }
+    std::memcpy(payload, indices, std::size_t{indexCount} * 2);
+    std::byte* next = payload + indexBytes;
+    pack(next, positions.data, positions.stride, 12, vertexCount);
+    next += std::size_t{vertexCount} * 12;
+    if (hasNormals) {
+        pack(next, normals.data, normals.stride, 12, vertexCount);
+        next += std::size_t{vertexCount} * 12;
+    }
+    if (hasTexCoords) {
+        pack(next, texCoords.data, texCoords.stride, 8, vertexCount);
+        next += std::size_t{vertexCount} * 8;
+    }
+    if (hasColors) {
+        pack(next, colors.data, colors.stride, 4, vertexCount);
+    }
+}
+
+} // namespace t5de

adapter/engine.hpp

@@ -0,0 +1,104 @@
+#pragma once
+// The adapter's engine: what the client draws with. Everything is recorded for the renderer process, which draws the
+// 3D view and the render targets it makes. The client's own Direct3D renderer gets state and resources too (as a
+// fallback, and for reading textures back), but while the renderer process covers the whole view, the client's
+// renderer skips its frames' clears and draws. When the renderer process doesn't cover it (it failed, or shows only
+// part of the view, for comparing) the client's renderer draws everything, from the next frame on.
+
+#include <windows.h>
+
+#include <cstdint>
+#include <memory>
+
+#include "recorder.hpp"
+#include "t5de/imvu/render_engine.hpp"
+
+namespace t5de {
+
+class Engine final : public imvu::PiRenderEngine {
+public:
+    // recorder may be inactive (no renderer process); window is the 3D window drawn into (frame_pacer.hpp), or null.
+    Engine(imvu::SharedPtr<imvu::PiRenderEngine> inner, std::shared_ptr<Recorder> recorder, HWND window);
+    ~Engine() override;
+
+    void resizeFrameBuffer(imvu::Vec2i size) override;
+    void enable2dFrameBuffer() override;
+    void clear(std::uint32_t flags, imvu::Color color) override;
+    void setProjection(imvu::Vec2i viewport, const imvu::Mat4f& projection) override;
+    void setModelSpace(const imvu::Transform& model) override;
+    void setViewSpace(const imvu::Transform& view) override;
+    void setTextures(imvu::PiRenderTexture* texture0, imvu::PiRenderTexture* texture1) override;
+    void setDepthTestingOn(bool on) override;
+    void setDepthWritingOn(bool on) override;
+    void setBlendMode(imvu::RenderBlendMode mode) override;
+    void setAlphaTestingOn(bool on) override;
+    void setAlphaTestValue(float value) override;
+    void setBlendingOn(bool on) override;
+    void setBackFaceCullingOn(bool on) override;
+    void setNormalInvertingOn(bool on) override;
+    void setLightingOn(bool on) override;
+    void setLightProperties(std::uint32_t index, const imvu::LightProperties& light) override;
+    void setFogOn(bool on) override;
+    void setFogAttributes(float start, float end, imvu::Color color) override;
+    void setTextureTransformMatrixIdentity(std::uint32_t stage) override;
+    void setTextureTransformMatrix(std::uint32_t stage, const imvu::TextureTransform& transform) override;
+    void setEnvironmentAmbient(imvu::Color color) override;
+    imvu::PiRenderTexture* newRenderTexture(const imvu::Pixmap& pixmap, std::uint32_t flags) override;
+    imvu::PiInternalIndexBuffer* newIndexBuffer(std::uint32_t count, const std::uint16_t* indices) override;
+    imvu::PiInternalVertexBuffer* newStaticVertexBuffer(const void* data, std::uint32_t stride,
+                                                        std::uint32_t elementSize,
+                                                        std::uint32_t elementCount) override;
+    imvu::PiInternalVertexBuffer* newDynamicVertexBuffer(std::uint32_t elementSize,
+                                                         std::uint32_t elementCount) override;
+    imvu::SharedPtr<imvu::PiPixmapRenderTarget> newPixmapRenderTarget(imvu::Vec2i size) override;
+    imvu::SharedPtr<imvu::PiTextureRenderTarget> newTextureRenderTarget(imvu::Vec2i size) override;
+    void beginRendering(imvu::PiRenderTarget* target) override;
+    void endRendering() override;
+    void drawTriangles(imvu::PiInternalIndexBuffer* indices, imvu::PiInternalVertexBuffer* positions,
+                       imvu::PiInternalVertexBuffer* normals, imvu::PiInternalVertexBuffer* texCoords,
+                       imvu::PiInternalVertexBuffer* colors) override;
+    void drawLine(imvu::Vec3f from, imvu::Vec3f to, imvu::Color color) override;
+    void drawPointSprites(const imvu::PointSpriteVector& sprites) override;
+    void drawTrianglesFromMemory(std::uint32_t vertexCount, std::uint32_t indexCount, const std::uint16_t* indices,
+                                 const imvu::VertexAttributeArray<imvu::Vec3f>& positions,
+                                 const imvu::VertexAttributeArray<imvu::Vec3f>& normals,
+                                 const imvu::VertexAttributeArray<imvu::Vec2f>& texCoords,
+                                 const imvu::VertexAttributeArray<imvu::Color>& colors) override;
+
+private:
+    void setState(protocol::State state, std::uint32_t value);
+    // Whether the client's renderer should draw this frame's clears and draws.
+    [[nodiscard]] bool innerDraws() const { return !takenOver_; }
+
+    imvu::SharedPtr<imvu::PiRenderEngine> inner_;
+    std::shared_ptr<Recorder> recorder_;
+    HWND window_;
+    std::uint64_t frames_ = 0;
+    bool takenOver_ = false; // this frame is drawn by the renderer process only
+    imvu::PiRenderTarget* ourTarget_ = nullptr; // this frame's render target, if it's one of ours
+    int foreignLogged_ = 0; // diagnostics: textures the client renderer made, render targets
+
+    // Diagnostics: what the client draws, summed over 300 frames and logged (the first few times).
+    struct Stats {
+        std::uint32_t triangles = 0;        // drawTriangles with our buffers
+        std::uint32_t foreignTriangles = 0; // drawTriangles with buffers that aren't ours (not drawn)
+        std::uint32_t indexed = 0;          // drawTrianglesFromMemory with indices
+        std::uint32_t unindexed = 0;        // drawTrianglesFromMemory without
+        std::uint32_t sprites = 0;
+        std::uint32_t lines = 0;
+        std::uint32_t flat = 0; // setProjection with an orthographic projection (2D)
+    };
+    Stats stats_;
+    LARGE_INTEGER statsStart_{}; // when the stats' 300 frames started
+    LARGE_INTEGER frameStart_{}; // when the current frame began
+    std::int64_t lastWindowFrame_ = 0; // when the last window frame began
+    double longestGap_ = 0;      // the stats' longest time between window frames' beginnings, in seconds
+    double frameSeconds_ = 0;    // the stats' window frames' time, beginRendering to endRendering
+    bool windowFrame_ = false;   // the current frame is drawn into the window
+    bool innerFrame_ = false;    // the current frame is begun in the client's renderer
+    std::int64_t innerTicksAtStats_ = 0; // innerTicks when the stats' 300 frames started
+    int statsLogged_ = 0;
+
+};
+
+} // namespace t5de

adapter/frame_pacer.cpp

@@ -0,0 +1,167 @@
+#include "frame_pacer.hpp"
+
+#include <algorithm>
+#include <cstdint>
+#include <mutex>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include "log.hpp"
+#include "scene_hooks.hpp"
+
+namespace t5de::frame_pacer {
+
+namespace {
+
+// The client's own rate: its ticks already draw these frames.
+constexpr DWORD clientRate = 30;
+// The client is left idle at least this share of a frame's time between frames.
+constexpr double idleShare = 1.0 / 3.0;
+// The client's tick (SceneWindow.dll's millisecondsPerFrame).
+constexpr double tickSeconds = 0.033;
+// An extra frame must end at least this long before the next tick is due.
+constexpr double tickMargin = 0.001;
+
+// The user's frame rate, from the registry (unset or unreadable: the client's own).
+DWORD read_rate()
+{
+    DWORD rate = 0;
+    DWORD size = sizeof(rate);
+    if (RegGetValueW(HKEY_CURRENT_USER, L"Software\\T5DE\\Graphics", L"FrameRate", RRF_RT_REG_DWORD, nullptr, &rate,
+                     &size) != ERROR_SUCCESS) {
+        return clientRate;
+    }
+    return rate;
+}
+
+double seconds(std::int64_t counter)
+{
+    static const double frequency = [] {
+        LARGE_INTEGER value;
+        QueryPerformanceFrequency(&value);
+        return static_cast<double>(value.QuadPart);
+    }();
+    return static_cast<double>(counter) / frequency;
+}
+
+double now_seconds()
+{
+    LARGE_INTEGER counter;
+    QueryPerformanceCounter(&counter);
+    return seconds(counter.QuadPart);
+}
+
+class Pacer {
+public:
+    static Pacer& get()
+    {
+        static Pacer pacer;
+        return pacer;
+    }
+
+    void add(HWND window)
+    {
+        const std::scoped_lock lock(mutex_);
+        windows_.push_back({.window = window});
+        if (!started_) {
+            started_ = true;
+            std::thread([this] { run(); }).detach(); // runs while the client does
+        }
+    }
+
+    void remove(HWND window)
+    {
+        const std::scoped_lock lock(mutex_);
+        std::erase_if(windows_, [window](const Window& w) { return w.window == window; });
+    }
+
+    void frameDrawn(HWND window, double seconds)
+    {
+        const std::scoped_lock lock(mutex_);
+        for (Window& w : windows_) {
+            if (w.window == window) {
+                w.pending = false;
+                w.frameTime = w.frameTime == 0 ? seconds : w.frameTime * 0.9 + seconds * 0.1;
+                w.drawnAt = now_seconds();
+            }
+        }
+    }
+
+private:
+    struct Window {
+        HWND window;
+        bool pending = false;  // a repaint asked for and not yet drawn
+        double frameTime = 0;  // seconds a frame takes the client, averaged
+        double drawnAt = 0;    // when its last frame was drawn
+        double askedAt = 0;    // when a repaint was last asked for
+    };
+
+    // Re-reads the setting now and then; above the client's rate, asks each window for repaints at the rate, or as often
+    // as leaves the client its idle time.
+    void run()
+    {
+        HANDLE timer = CreateWaitableTimerExW(nullptr, nullptr, CREATE_WAITABLE_TIMER_HIGH_RESOLUTION, TIMER_ALL_ACCESS);
+        double checked = 0;
+        DWORD rate = clientRate;
+        for (;;) {
+            const double now = now_seconds();
+            if (now - checked >= 0.5) {
+                checked = now;
+                const DWORD read = read_rate();
+                if (read != rate) {
+                    rate = read;
+                    log::info("frame pacer: frame rate {}", rate == 0 ? std::string("uncapped") : std::to_string(rate));
+                }
+            }
+            if (rate != 0 && rate <= clientRate) {
+                Sleep(100);
+                continue;
+            }
+            const double interval = rate == 0 ? 0 : 1.0 / rate;
+            // The next tick, if known (scene_hooks.hpp): extra frames mustn't hold it up, or the client catches up two
+            // steps at once (visible hitches).
+            const std::int64_t lastStep = scene_hooks::lastStep();
+            const double untilTick = lastStep != 0 ? seconds(lastStep) + tickSeconds - now : tickSeconds;
+            {
+                const std::scoped_lock lock(mutex_);
+                for (Window& w : windows_) {
+                    if (w.pending && now - w.askedAt < 0.25) {
+                        continue; // not drawn yet (asked again after a while: the client may have skipped it)
+                    }
+                    if (untilTick > -tickSeconds && untilTick < w.frameTime + tickMargin) {
+                        continue; // the tick is due: it draws a frame of its own
+                    }
+                    // Since the last frame ended: the rest of the interval since it began, and the idle time.
+                    if (now - w.drawnAt >= std::max(interval - w.frameTime, w.frameTime * idleShare)) {
+                        w.pending = true;
+                        w.askedAt = now;
+                        InvalidateRect(w.window, nullptr, FALSE);
+                    }
+                }
+            }
+            // Wake often enough for the rate (1 ms at most when uncapped).
+            const double wait = std::clamp(interval / 4, 0.0005, 0.004);
+            LARGE_INTEGER due{.QuadPart = -static_cast<LONGLONG>(wait * 10'000'000)}; // relative, 100 ns units
+            if (timer != nullptr && SetWaitableTimer(timer, &due, 0, nullptr, nullptr, FALSE)) {
+                WaitForSingleObject(timer, INFINITE);
+            } else {
+                Sleep(1);
+            }
+        }
+    }
+
+    std::mutex mutex_;
+    std::vector<Window> windows_;
+    bool started_ = false;
+};
+
+} // namespace
+
+void add(HWND window) { Pacer::get().add(window); }
+
+void remove(HWND window) { Pacer::get().remove(window); }
+
+void frameDrawn(HWND window, double seconds) { Pacer::get().frameDrawn(window, seconds); }
+
+} // namespace t5de::frame_pacer

adapter/frame_pacer.hpp

@@ -0,0 +1,25 @@
+#pragma once
+// Extra frames between the client's 30-per-second ticks. The client draws a 3D window's frame when the window gets
+// WM_PAINT, and steps its scene on its own timer (SceneWindow.dll's runApp: a step, then the window is invalidated);
+// its message loop also wakes for WM_PAINT between steps. So asking the windows to repaint more often makes the client
+// draw more frames, without stepping the scene. The rate is the user's (T5DE's settings, Graphics: HKCU\Software\T5DE\
+// Graphics, FrameRate): 30, the client's own and the default, adds nothing; 60, 120, 240 or 360 add frames between
+// ticks; 0 is uncapped.
+//
+// The rate counts all of a window's frames, the client's own included: a window is asked for one once its last frame
+// is drawn and the interval since it began has passed. Drawing runs on the client's main thread, with its input and
+// interface, so the client is also always left idle a third of a frame's time between frames: when the rate can't be
+// reached, the client draws as many frames as that allows.
+
+#include <windows.h>
+
+namespace t5de::frame_pacer {
+
+// A 3D window an engine draws into: repainted at the user's frame rate while added.
+void add(HWND window);
+void remove(HWND window);
+
+// A frame drawn into window, taking the client this long (beginRendering to endRendering).
+void frameDrawn(HWND window, double seconds);
+
+} // namespace t5de::frame_pacer

adapter/inner_timing.hpp

@@ -0,0 +1,31 @@
+#pragma once
+// Diagnostics: the time spent in the client renderer's methods (the engine's inner engine, and the resources it made),
+// summed, so the stats can tell it from the rest of a frame.
+
+#include <windows.h>
+
+#include <cstdint>
+
+namespace t5de {
+
+// QueryPerformanceCounter ticks spent in the client renderer's methods so far.
+inline std::int64_t innerTicks = 0;
+
+// Adds its lifetime to innerTicks.
+class InnerCall {
+public:
+    InnerCall() { QueryPerformanceCounter(&start_); }
+    InnerCall(const InnerCall&) = delete;
+    InnerCall& operator=(const InnerCall&) = delete;
+    ~InnerCall()
+    {
+        LARGE_INTEGER end;
+        QueryPerformanceCounter(&end);
+        innerTicks += end.QuadPart - start_.QuadPart;
+    }
+
+private:
+    LARGE_INTEGER start_;
+};
+
+} // namespace t5de

adapter/pixmap.cpp

@@ -0,0 +1,83 @@
+#include "pixmap.hpp"
+
+#include <windows.h>
+
+namespace t5de {
+
+namespace {
+
+using Getter = unsigned(__thiscall*)(const imvu::Pixmap*);
+using PixelsGetter = std::uint32_t*(__thiscall*)(const imvu::Pixmap*);
+using SizeConstructor = imvu::Pixmap*(__thiscall*)(void*, int, int);
+using DefaultConstructor = imvu::Pixmap*(__thiscall*)(void*);
+using CopyConstructor = imvu::Pixmap*(__thiscall*)(void*, const imvu::Pixmap*);
+using Destructor = void(__thiscall*)(imvu::Pixmap*);
+
+struct Methods {
+    Getter width = nullptr;
+    Getter height = nullptr;
+    Getter rowBytes = nullptr;
+    PixelsGetter pixels = nullptr;
+    SizeConstructor construct = nullptr;
+    DefaultConstructor constructEmpty = nullptr;
+    CopyConstructor copy = nullptr;
+    Destructor destroy = nullptr;
+};
+
+const Methods& methods()
+{
+    static const Methods methods = [] {
+        Methods found;
+        if (HMODULE module = GetModuleHandleW(L"pixmap.dll")) {
+            found.width = reinterpret_cast<Getter>(GetProcAddress(module, "?width@Pixmap@@QBEIXZ"));
+            found.height = reinterpret_cast<Getter>(GetProcAddress(module, "?height@Pixmap@@QBEIXZ"));
+            found.rowBytes = reinterpret_cast<Getter>(GetProcAddress(module, "?rowBytes@Pixmap@@QBEIXZ"));
+            found.pixels = reinterpret_cast<PixelsGetter>(GetProcAddress(module, "?pixels@Pixmap@@QBEPAIXZ"));
+            found.construct = reinterpret_cast<SizeConstructor>(GetProcAddress(module, "??0Pixmap@@QAE@HH@Z"));
+            found.constructEmpty = reinterpret_cast<DefaultConstructor>(GetProcAddress(module, "??0Pixmap@@QAE@XZ"));
+            found.copy = reinterpret_cast<CopyConstructor>(GetProcAddress(module, "??0Pixmap@@QAE@ABV0@@Z"));
+            found.destroy = reinterpret_cast<Destructor>(GetProcAddress(module, "??1Pixmap@@QAE@XZ"));
+        }
+        return found;
+    }();
+    return methods;
+}
+
+} // namespace
+
+std::optional<PixmapPixels> pixmap_pixels(const imvu::Pixmap& pixmap)
+{
+    const Methods& m = methods();
+    if (m.width == nullptr || m.height == nullptr || m.rowBytes == nullptr || m.pixels == nullptr) {
+        return std::nullopt;
+    }
+    return PixmapPixels{m.width(&pixmap), m.height(&pixmap), m.rowBytes(&pixmap), m.pixels(&pixmap)};
+}
+
+OwnedPixmap::OwnedPixmap(int width, int height)
+{
+    const Methods& m = methods();
+    if (m.construct != nullptr && m.constructEmpty != nullptr && m.copy != nullptr && m.destroy != nullptr) {
+        m.construct(storage_, width, height);
+        valid_ = true;
+    }
+}
+
+OwnedPixmap::~OwnedPixmap()
+{
+    if (valid_) {
+        methods().destroy(reinterpret_cast<imvu::Pixmap*>(storage_));
+    }
+}
+
+imvu::Pixmap* OwnedPixmap::copyTo(imvu::Pixmap* result) const
+{
+    const Methods& m = methods();
+    if (valid_) {
+        return m.copy(result, &get());
+    }
+    // Without pixmap.dll's methods there's nothing to construct one with (IMVU's own code would have failed already).
+    return m.constructEmpty != nullptr ? m.constructEmpty(result) : result;
+}
+
+} // namespace t5de

adapter/pixmap.hpp

@@ -0,0 +1,45 @@
+#pragma once
+// IMVU's images (Pixmap), through pixmap.dll's exported methods rather than depending on their layout (only their
+// size, for making our own).
+
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+
+#include "t5de/imvu/types.hpp"
+
+namespace t5de {
+
+struct PixmapPixels {
+    std::uint32_t width;
+    std::uint32_t height;
+    std::uint32_t rowBytes;
+    std::uint32_t* pixels; // 0xAARRGGBB, rows rowBytes apart
+};
+
+// Null if pixmap.dll's methods can't be found.
+std::optional<PixmapPixels> pixmap_pixels(const imvu::Pixmap& pixmap);
+
+// A Pixmap of our own, made and destroyed by pixmap.dll.
+class OwnedPixmap {
+public:
+    // Width by height; invalid if pixmap.dll's methods can't be found.
+    OwnedPixmap(int width, int height);
+    OwnedPixmap(const OwnedPixmap&) = delete;
+    OwnedPixmap& operator=(const OwnedPixmap&) = delete;
+    ~OwnedPixmap();
+
+    [[nodiscard]] bool valid() const { return valid_; }
+    [[nodiscard]] const imvu::Pixmap& get() const { return *reinterpret_cast<const imvu::Pixmap*>(storage_); }
+
+    // Constructs a copy in result (raw memory for a Pixmap, as for a Pixmap returned by value); an empty Pixmap if
+    // this one isn't valid.
+    imvu::Pixmap* copyTo(imvu::Pixmap* result) const;
+
+private:
+    // sizeof(Pixmap) in pixmap.dll: its constructors set 7 fields.
+    alignas(4) std::byte storage_[28];
+    bool valid_ = false;
+};
+
+} // namespace t5de

adapter/plugin.cpp

@@ -1,12 +1,17 @@
 // The renderer plugin's entry points, which SceneWindow.dll's createDLLRenderer looks up by name (exported
-// undecorated by plugin.def). For now the renderer is the pass-through: IMVU's Direct3D engine, wrapped.
+// undecorated by plugin.def). The engine is the adapter's (engine.hpp): IMVU's Direct3D engine draws, and the
+// renderer process draws over part of it.
 
 #include <windows.h>
 
 #include <exception>
+#include <string_view>
 
 #include "log.hpp"
-#include "passthrough_engine.hpp"
+#include "engine.hpp"
+#include "recorder.hpp"
+#include "renderer_process.hpp"
+#include "scene_hooks.hpp"
 #include "t5de/imvu/render_engine.hpp"
 
 namespace {
@@ -29,6 +34,19 @@ imvu::SharedPtr<imvu::PiRenderEngine> create_imvu_engine(imvu::SharedPtr<imvu::I
     return create(std::move(window), imvu::RendererType::Direct3D);
 }
 
+// What the renderer process draws: T5DE_RENDERER_VIEW=off, split (the right half), full (the default) or compare.
+// (The renderer process can also be switched while it runs: renderer/main.cpp.)
+protocol::View view()
+{
+    wchar_t value[16] = {};
+    GetEnvironmentVariableW(L"T5DE_RENDERER_VIEW", value, 16);
+    const std::wstring_view setting = value;
+    return setting == L"off"       ? protocol::View::Off
+           : setting == L"split"   ? protocol::View::Split
+           : setting == L"compare" ? protocol::View::Compare
+                                   : protocol::View::Full;
+}
+
 } // namespace
 
 extern "C" int __cdecl isRenderEngineSupported() { return 1; }
@@ -39,11 +57,16 @@ extern "C" imvu::SharedPtr<imvu::PiRenderEngine> __cdecl createRenderEngine(imvu
 {
     try {
         log::info("createRenderEngine: window {}", static_cast<void*>(window.get()));
+        HWND hwnd = window ? window->getPlatformWindow() : nullptr;
+        scene_hooks::install();
         auto inner = create_imvu_engine(std::move(window));
         if (!inner) {
             return {};
         }
-        return imvu::SharedPtr<imvu::PiRenderEngine>(std::make_unique<PassthroughEngine>(std::move(inner)));
+        const protocol::View shown = view();
+        auto renderer = hwnd != nullptr && shown != protocol::View::Off ? RendererProcess::start(hwnd, shown) : nullptr;
+        return imvu::SharedPtr<imvu::PiRenderEngine>(std::make_unique<Engine>(
+            std::move(inner), std::make_shared<Recorder>(std::move(renderer)), hwnd));
     } catch (const std::exception& e) {
         // Exceptions mustn't cross into IMVU's code (a different C++ runtime).
         log::info("createRenderEngine failed: {}", e.what());

adapter/recorder.cpp

@@ -0,0 +1,131 @@
+#include "recorder.hpp"
+
+#include <cstring>
+
+#include "log.hpp"
+#include "pixmap.hpp"
+
+namespace t5de {
+
+namespace {
+
+// Between frames, recorded commands (mostly textures and buffers being loaded) are sent once they reach this size.
+constexpr std::size_t flushSize = 4 * 1024 * 1024;
+
+} // namespace
+
+void pack(std::byte* destination, const void* source, std::uint32_t stride, std::uint32_t elementSize,
+          std::uint32_t count)
+{
+    const auto* from = static_cast<const std::byte*>(source);
+    if (stride == 0 || stride == elementSize) {
+        std::memcpy(destination, from, std::size_t{elementSize} * count);
+        return;
+    }
+    for (std::uint32_t i = 0; i < count; ++i) {
+        std::memcpy(destination + std::size_t{i} * elementSize, from + std::size_t{i} * stride, elementSize);
+    }
+}
+
+Recorder::Recorder(std::unique_ptr<RendererProcess> process) : process_(std::move(process)) {}
+
+void Recorder::flush(bool endsFrame)
+{
+    if (!active()) {
+        writer_.clear();
+        return;
+    }
+    LARGE_INTEGER start, end, frequency;
+    QueryPerformanceCounter(&start);
+    process_->send(writer_.bytes(), endsFrame);
+    QueryPerformanceCounter(&end);
+    QueryPerformanceFrequency(&frequency);
+    counters_.bytes += writer_.size();
+    counters_.sendSeconds += static_cast<double>(end.QuadPart - start.QuadPart) / static_cast<double>(frequency.QuadPart);
+    writer_.clear();
+}
+
+void Recorder::flushIfLarge()
+{
+    if (writer_.size() >= flushSize) {
+        flush(false);
+    }
+}
+
+void Recorder::addPixels(protocol::Op op, std::uint32_t id, const imvu::Pixmap& pixmap, std::uint32_t flags)
+{
+    const auto pixels = pixmap_pixels(pixmap);
+    if (!pixels || pixels->pixels == nullptr) {
+        return;
+    }
+    const std::size_t rowSize = std::size_t{pixels->width} * 4;
+    std::byte* payload = nullptr;
+    if (op == protocol::Op::CreateTexture) {
+        payload = add(op, protocol::CreateTexture{id, pixels->width, pixels->height, flags}, rowSize * pixels->height);
+    } else {
+        payload = add(op, protocol::UpdateTexture{id, pixels->width, pixels->height}, rowSize * pixels->height);
+    }
+    if (payload == nullptr) {
+        return;
+    }
+    const auto* rows = reinterpret_cast<const std::byte*>(pixels->pixels);
+    for (std::uint32_t y = 0; y < pixels->height; ++y) {
+        std::memcpy(payload + y * rowSize, rows + std::size_t{y} * pixels->rowBytes, rowSize);
+    }
+    flushIfLarge();
+}
+
+std::uint32_t Recorder::createRenderTarget(std::uint32_t width, std::uint32_t height)
+{
+    const std::uint32_t id = nextId_++;
+    add(protocol::Op::CreateRenderTarget, protocol::CreateRenderTarget{id, width, height});
+    return id;
+}
+
+std::span<const std::byte> Recorder::readBack()
+{
+    return active() ? process_->readBack() : std::span<const std::byte>{};
+}
+
+std::uint32_t Recorder::createTexture(const imvu::Pixmap& pixmap, std::uint32_t flags)
+{
+    const std::uint32_t id = nextId_++;
+    addPixels(protocol::Op::CreateTexture, id, pixmap, flags);
+    return id;
+}
+
+void Recorder::updateTexture(std::uint32_t id, const imvu::Pixmap& pixmap)
+{
+    addPixels(protocol::Op::UpdateTexture, id, pixmap, 0);
+}
+
+void Recorder::destroyTexture(std::uint32_t id) { add(protocol::Op::DestroyTexture, protocol::DestroyTexture{id}); }
+
+std::uint32_t Recorder::createBuffer(protocol::BufferKind kind, const void* data, std::uint32_t stride,
+                                     std::uint32_t elementSize, std::uint32_t count)
+{
+    const std::uint32_t id = nextId_++;
+    const std::size_t size = data != nullptr ? std::size_t{elementSize} * count : 0;
+    if (std::byte* payload = add(protocol::Op::CreateBuffer, protocol::CreateBuffer{id, kind, elementSize, count}, size);
+        payload != nullptr && size != 0) {
+        pack(payload, data, stride, elementSize, count);
+    }
+    flushIfLarge();
+    return id;
+}
+
+void Recorder::updateBuffer(std::uint32_t id, const void* data, std::uint32_t stride, std::uint32_t elementSize,
+                            std::uint32_t count)
+{
+    const std::size_t size = std::size_t{elementSize} * count;
+    ++counters_.bufferUpdates;
+    counters_.bufferBytes += size;
+    if (std::byte* payload = add(protocol::Op::UpdateBuffer, protocol::UpdateBuffer{id, elementSize, count}, size);
+        payload != nullptr && data != nullptr) {
+        pack(payload, data, stride, elementSize, count);
+    }
+}
+
+void Recorder::destroyBuffer(std::uint32_t id) { add(protocol::Op::DestroyBuffer, protocol::DestroyBuffer{id}); }
+
+} // namespace t5de

adapter/recorder.hpp

@@ -0,0 +1,79 @@
+#pragma once
+// Records what the client draws as commands (include/t5de/protocol/commands.hpp) and sends them to the renderer
+// process. Shared by an engine and the resources it creates (which can outlive it); once the renderer process is
+// gone, it records nothing.
+
+#include <cstdint>
+#include <memory>
+#include <span>
+#include <utility>
+
+#include "renderer_process.hpp"
+#include "t5de/imvu/types.hpp"
+#include "t5de/protocol/commands.hpp"
+
+namespace t5de {
+
+class Recorder {
+public:
+    explicit Recorder(std::unique_ptr<RendererProcess> process);
+
+    [[nodiscard]] bool active() const { return process_ && process_->alive(); }
+
+    // Whether the renderer process draws the whole 3D view, so the client's renderer needn't.
+    [[nodiscard]] bool covering() const { return process_ && process_->covering(); }
+
+    // Records a command (if active); returns its payload to fill, or null.
+    template <class Body>
+    std::byte* add(protocol::Op op, const Body& body, std::size_t payloadSize = 0)
+    {
+        if (!active()) {
+            return nullptr;
+        }
+        std::byte* payload = writer_.add(op, body, payloadSize);
+        return payload;
+    }
+
+    // Sends what's recorded: at the end of each frame, and between frames when a lot is waiting (resources).
+    void flush(bool endsFrame);
+    void flushIfLarge();
+
+    std::uint32_t createTexture(const imvu::Pixmap& pixmap, std::uint32_t flags);
+    // Destroyed with destroyTexture.
+    std::uint32_t createRenderTarget(std::uint32_t width, std::uint32_t height);
+    // After flushing a frame that reads its render target back: its pixels (RendererProcess::readBack).
+    std::span<const std::byte> readBack();
+    void updateTexture(std::uint32_t id, const imvu::Pixmap& pixmap);
+    void destroyTexture(std::uint32_t id);
+
+    // Copies count elements of elementSize bytes, stride bytes apart (0: packed), from data (null: none yet).
+    std::uint32_t createBuffer(protocol::BufferKind kind, const void* data, std::uint32_t stride,
+                               std::uint32_t elementSize, std::uint32_t count);
+    void updateBuffer(std::uint32_t id, const void* data, std::uint32_t stride, std::uint32_t elementSize,
+                      std::uint32_t count);
+    void destroyBuffer(std::uint32_t id);
+
+    // Diagnostics: what's been sent, and the time spent sending (waiting for the renderer process to take it).
+    struct Counters {
+        std::uint64_t bytes = 0;
+        double sendSeconds = 0;
+        std::uint32_t bufferUpdates = 0;
+        std::uint64_t bufferBytes = 0;
+    };
+    // Returns the counters since the last call.
+    Counters takeCounters() { return std::exchange(counters_, {}); }
+
+private:
+    void addPixels(protocol::Op op, std::uint32_t id, const imvu::Pixmap& pixmap, std::uint32_t flags);
+
+    std::unique_ptr<RendererProcess> process_;
+    protocol::Writer writer_;
+    std::uint32_t nextId_ = 1;
+    Counters counters_;
+};
+
+// Copies count elements of elementSize bytes, stride bytes apart (0: packed), into destination, packed.
+void pack(std::byte* destination, const void* source, std::uint32_t stride, std::uint32_t elementSize,
+          std::uint32_t count);
+
+} // namespace t5de

adapter/renderer_process.cpp

@@ -0,0 +1,244 @@
+#include "renderer_process.hpp"
+
+#include <algorithm>
+#include <cstring>
+#include <filesystem>
+#include <format>
+#include <mutex>
+#include <string>
+
+#include "log.hpp"
+
+namespace t5de {
+
+namespace {
+
+// How long to wait for the renderer process to take a chunk before giving up on it.
+constexpr DWORD consumeTimeout = 5000;
+
+// The folder this DLL is in: the client's program folder.
+std::filesystem::path module_folder()
+{
+    HMODULE self = nullptr;
+    GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+                       reinterpret_cast<LPCWSTR>(&module_folder), &self);
+    wchar_t path[MAX_PATH];
+    GetModuleFileNameW(self, path, MAX_PATH);
+    return std::filesystem::path(path).parent_path();
+}
+
+std::string narrow(const std::wstring& text) { return std::filesystem::path(text).string(); }
+
+// The renderer process runs from a copy in %TEMP%\t5de-renderer, one per version of the program (by size and
+// modification time), so the program in the client's folder can be replaced (updated) while the client runs: the
+// next engine runs the new one. Copies no longer running are removed. Falls back to the program itself.
+std::filesystem::path running_copy(const std::filesystem::path& exe)
+{
+    std::error_code error;
+    const auto size = std::filesystem::file_size(exe, error);
+    const auto modified = std::filesystem::last_write_time(exe, error);
+    if (error) {
+        return exe;
+    }
+    const auto folder = std::filesystem::temp_directory_path(error) / L"t5de-renderer";
+    std::filesystem::create_directories(folder, error);
+    const auto copy = folder / std::format(L"t5de-renderer-{}-{}.exe", size, modified.time_since_epoch().count());
+    if (!std::filesystem::exists(copy, error)) {
+        for (const auto& old : std::filesystem::directory_iterator(folder, error)) {
+            std::filesystem::remove(old.path(), error); // fails, harmlessly, for copies still running
+        }
+        if (!CopyFileW(exe.c_str(), copy.c_str(), FALSE)) {
+            return exe;
+        }
+    }
+    return copy;
+}
+
+// The client's one renderer process, and the control section (protocol::Control) engines attach their channels
+// through. Started with the first engine; started again by the next one if it has exited.
+class Host {
+public:
+    static Host& get()
+    {
+        static Host host;
+        return host;
+    }
+
+    std::mutex& mutex() { return mutex_; }
+
+    // The next channel's name.
+    std::wstring nextChannel() const { return std::format(L"{}-{}", name_, channels_); }
+
+    // Tells the renderer process about the channel just created (nextChannel()), starting it if it isn't running.
+    // Returns a handle to the renderer process, the caller's to close; null if it can't.
+    HANDLE attach()
+    {
+        if (control_ == nullptr || (!running() && !startProcess())) {
+            return nullptr;
+        }
+        control_->channels = ++channels_;
+        SetEvent(attach_);
+        HANDLE process = nullptr;
+        DuplicateHandle(GetCurrentProcess(), process_, GetCurrentProcess(), &process, 0, FALSE, DUPLICATE_SAME_ACCESS);
+        return process;
+    }
+
+private:
+    Host() : name_(std::format(L"Local\\t5de-renderer-{}", GetCurrentProcessId()))
+    {
+        mapping_ = CreateFileMappingW(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, 0, sizeof(protocol::Control),
+                                      name_.c_str());
+        attach_ = CreateEventW(nullptr, FALSE, FALSE, (name_ + protocol::attachEventSuffix).c_str());
+        if (mapping_ != nullptr && attach_ != nullptr) {
+            control_ = static_cast<protocol::Control*>(
+                MapViewOfFile(mapping_, FILE_MAP_ALL_ACCESS, 0, 0, sizeof(protocol::Control)));
+        }
+        if (control_ == nullptr) {
+            log::info("renderer process: can't create the control section: error {}", GetLastError());
+            return;
+        }
+        *control_ = {.version = protocol::version, .channels = 0};
+    }
+
+    [[nodiscard]] bool running() const { return process_ != nullptr && WaitForSingleObject(process_, 0) == WAIT_TIMEOUT; }
+
+    bool startProcess()
+    {
+        if (process_ != nullptr) {
+            CloseHandle(process_);
+            process_ = nullptr;
+        }
+        const auto exe = running_copy(module_folder() / L"t5de-renderer.exe");
+        std::wstring command =
+            std::format(L"\"{}\" --control {} --parent {}", exe.wstring(), name_, GetCurrentProcessId());
+        STARTUPINFOW startup{.cb = sizeof(STARTUPINFOW)};
+        PROCESS_INFORMATION process{};
+        if (!CreateProcessW(exe.c_str(), command.data(), nullptr, nullptr, FALSE, 0, nullptr, nullptr, &startup,
+                            &process)) {
+            log::info("renderer process: can't start {}: error {}", exe.string(), GetLastError());
+            return false;
+        }
+        CloseHandle(process.hThread);
+        process_ = process.hProcess;
+        log::info("renderer process: started {} (pid {})", exe.string(), process.dwProcessId);
+        return true;
+    }
+
+    std::mutex mutex_;
+    std::wstring name_;
+    HANDLE mapping_ = nullptr;
+    HANDLE attach_ = nullptr;
+    protocol::Control* control_ = nullptr;
+    HANDLE process_ = nullptr;
+    std::uint32_t channels_ = 0;
+};
+
+} // namespace
+
+std::unique_ptr<RendererProcess> RendererProcess::start(HWND window, protocol::View view)
+{
+    Host& host = Host::get();
+    const std::scoped_lock lock(host.mutex());
+    const std::wstring name = host.nextChannel();
+    constexpr DWORD size = sizeof(protocol::Channel) + protocol::channelCapacity;
+
+    std::unique_ptr<RendererProcess> renderer(new RendererProcess());
+    renderer->mapping_ = CreateFileMappingW(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, 0, size, name.c_str());
+    if (renderer->mapping_ == nullptr) {
+        log::info("renderer process: can't create the channel: error {}", GetLastError());
+        return nullptr;
+    }
+    renderer->channel_ =
+        static_cast<protocol::Channel*>(MapViewOfFile(renderer->mapping_, FILE_MAP_ALL_ACCESS, 0, 0, size));
+    renderer->ready_ = CreateEventW(nullptr, FALSE, FALSE, (name + protocol::readyEventSuffix).c_str());
+    renderer->consumed_ = CreateEventW(nullptr, FALSE, TRUE, (name + protocol::consumedEventSuffix).c_str());
+    renderer->read_ = CreateEventW(nullptr, FALSE, FALSE, (name + protocol::readEventSuffix).c_str());
+    if (renderer->channel_ == nullptr || renderer->ready_ == nullptr || renderer->consumed_ == nullptr
+        || renderer->read_ == nullptr) {
+        log::info("renderer process: can't set up the channel: error {}", GetLastError());
+        return nullptr;
+    }
+    renderer->data_ = reinterpret_cast<std::byte*>(renderer->channel_ + 1);
+    *renderer->channel_ = {.version = protocol::version,
+                           .closing = 0,
+                           .window = reinterpret_cast<std::uintptr_t>(window),
+                           .frames = 0,
+                           .view = view,
+                           .capacity = protocol::channelCapacity,
+                           .chunkSize = 0,
+                           .chunkFlags = 0,
+                           .covering = 0,
+                           .readSize = 0};
+
+    // The renderer's window goes on top of the client's 3D view, as a child window. The client's window mustn't clip
+    // its children (WS_CLIPCHILDREN, which the client creates it with): the client draws a frame when its window gets
+    // WM_PAINT, which a window entirely covered by clipped children never gets (it then drew about once a second). The
+    // renderer's swap chain is a flip model one, which the compositor shows above the client's drawing anyway.
+    SetWindowLongW(window, GWL_STYLE, GetWindowLongW(window, GWL_STYLE) & ~WS_CLIPCHILDREN);
+    renderer->process_ = host.attach();
+    if (renderer->process_ == nullptr) {
+        return nullptr;
+    }
+    log::info("renderer process: drawing channel {}", narrow(name));
+    return renderer;
+}
+
+RendererProcess::~RendererProcess()
+{
+    if (channel_ != nullptr) {
+        channel_->closing = 1;
+        if (ready_ != nullptr) {
+            SetEvent(ready_);
+        }
+        UnmapViewOfFile(channel_);
+    }
+    for (HANDLE handle : {ready_, consumed_, read_, mapping_, process_}) {
+        if (handle != nullptr) {
+            CloseHandle(handle);
+        }
+    }
+}
+
+bool RendererProcess::send(std::span<const std::byte> commands, bool endsFrame)
+{
+    if (!alive_) {
+        return false;
+    }
+    do {
+        const HANDLE waits[] = {consumed_, process_};
+        const DWORD result = WaitForMultipleObjects(2, waits, FALSE, consumeTimeout);
+        if (result != WAIT_OBJECT_0) {
+            log::info("renderer process: {}; giving up on it", result == WAIT_OBJECT_0 + 1 ? "exited" : "not responding");
+            alive_ = false;
+            return false;
+        }
+        const std::size_t size = std::min<std::size_t>(commands.size(), channel_->capacity);
+        std::memcpy(data_, commands.data(), size);
+        commands = commands.subspan(size);
+        channel_->chunkSize = static_cast<std::uint32_t>(size);
+        channel_->chunkFlags = endsFrame && commands.empty() ? protocol::chunkEndsFrame : 0;
+        if (endsFrame && commands.empty()) {
+            ++channel_->frames;
+        }
+        SetEvent(ready_);
+    } while (!commands.empty());
+    return true;
+}
+
+std::span<const std::byte> RendererProcess::readBack()
+{
+    if (!alive_) {
+        return {};
+    }
+    const HANDLE waits[] = {read_, process_};
+    const DWORD result = WaitForMultipleObjects(2, waits, FALSE, consumeTimeout);
+    if (result != WAIT_OBJECT_0) {
+        log::info("renderer process: {} reading back a frame; giving up on it",
+                  result == WAIT_OBJECT_0 + 1 ? "exited" : "not responding");
+        alive_ = false;
+        return {};
+    }
+    return {data_, std::min<std::size_t>(channel_->readSize, channel_->capacity)};
+}
+
+} // namespace t5de

adapter/renderer_process.hpp

@@ -0,0 +1,52 @@
+#pragma once
+// The renderer process (t5de-renderer.exe, 64-bit) an engine draws through: one for the whole client, started with
+// the first engine; each engine sends it the command stream through a shared memory channel of its own
+// (include/t5de/protocol/channel.hpp), and closes the channel when it's destroyed.
+
+#include <windows.h>
+
+#include <cstddef>
+#include <memory>
+#include <span>
+
+#include "t5de/protocol/channel.hpp"
+
+namespace t5de {
+
+class RendererProcess {
+public:
+    // A channel to the renderer process (t5de-renderer.exe from this DLL's folder, started if it isn't running),
+    // drawing into part of window; null if it can't.
+    static std::unique_ptr<RendererProcess> start(HWND window, protocol::View view);
+
+    RendererProcess(const RendererProcess&) = delete;
+    RendererProcess& operator=(const RendererProcess&) = delete;
+    ~RendererProcess();
+
+    // Sends commands, in as many chunks as they take; endsFrame marks the end of a frame. False if the renderer
+    // process is gone or stopped taking them (it's then given up on).
+    bool send(std::span<const std::byte> commands, bool endsFrame);
+
+    // After sending a frame that reads its render target back: waits for the pixels (protocol::Channel), valid until
+    // the next send. Empty if the renderer process couldn't, or is gone.
+    std::span<const std::byte> readBack();
+
+    [[nodiscard]] bool alive() const { return alive_; }
+
+    // Whether the renderer process covers the whole 3D view (protocol::Channel::covering).
+    [[nodiscard]] bool covering() const { return alive_ && channel_->covering != 0; }
+
+private:
+    RendererProcess() = default;
+
+    HANDLE mapping_ = nullptr;
+    HANDLE ready_ = nullptr;
+    HANDLE consumed_ = nullptr;
+    HANDLE read_ = nullptr;
+    HANDLE process_ = nullptr;
+    protocol::Channel* channel_ = nullptr;
+    std::byte* data_ = nullptr;
+    bool alive_ = true;
+};
+
+} // namespace t5de

adapter/resources.cpp

@@ -0,0 +1,192 @@
+#include "resources.hpp"
+
+#include <algorithm>
+#include <cstring>
+#include <mutex>
+#include <new>
+#include <unordered_set>
+
+#include "inner_timing.hpp"
+#include "log.hpp"
+
+namespace t5de {
+
+namespace {
+
+// Our live resources, by address.
+struct Registry {
+    std::mutex mutex;
+    std::unordered_set<const void*> objects;
+};
+
+Registry& registry()
+{
+    static Registry instance;
+    return instance;
+}
+
+void add(const void* object)
+{
+    const std::scoped_lock lock(registry().mutex);
+    registry().objects.insert(object);
+}
+
+void remove(const void* object)
+{
+    const std::scoped_lock lock(registry().mutex);
+    registry().objects.erase(object);
+}
+
+} // namespace
+
+bool ours(const void* object)
+{
+    if (object == nullptr) {
+        return false;
+    }
+    const std::scoped_lock lock(registry().mutex);
+    return registry().objects.contains(object);
+}
+
+Texture::Texture(imvu::PiRenderTexture* inner, std::shared_ptr<Recorder> recorder, std::uint32_t id)
+    : inner_(inner), recorder_(std::move(recorder)), id_(id)
+{
+    add(static_cast<imvu::PiRenderTexture*>(this));
+}
+
+Texture::Texture(std::shared_ptr<Recorder> recorder, std::uint32_t targetId, imvu::Vec2i size)
+    : inner_(nullptr), recorder_(std::move(recorder)), id_(targetId), size_(size), ownsId_(false)
+{
+    add(static_cast<imvu::PiRenderTexture*>(this));
+}
+
+Texture::~Texture()
+{
+    remove(static_cast<imvu::PiRenderTexture*>(this));
+    delete inner_; // through its virtual destructor: IMVU's code frees it
+    if (ownsId_) {
+        recorder_->destroyTexture(id_);
+    }
+}
+
+imvu::Vec2i Texture::size() const { return inner_ != nullptr ? inner_->size() : size_; }
+
+void Texture::updateRegions(const imvu::Pixmap& pixmap, const imvu::CompoundRegion& regions)
+{
+    if (inner_ != nullptr) {
+        { const InnerCall timed; inner_->updateRegions(pixmap, regions); }
+        recorder_->updateTexture(id_, pixmap); // all of it: the regions' layout isn't known
+    }
+}
+
+void Texture::update(const imvu::Pixmap& pixmap)
+{
+    if (inner_ != nullptr) {
+        { const InnerCall timed; inner_->update(pixmap); }
+        recorder_->updateTexture(id_, pixmap);
+    }
+}
+
+imvu::Pixmap* Texture::read(imvu::Pixmap* result) const
+{
+    if (inner_ != nullptr) {
+        return inner_->read(result);
+    }
+    // A render target's texture: not read back (not seen used); an image of its size.
+    log::info("texture: a render target's texture read; not supported, returning a blank image");
+    return OwnedPixmap(size_.x, size_.y).copyTo(result);
+}
+
+IndexBuffer::IndexBuffer(imvu::PiInternalIndexBuffer* inner, std::shared_ptr<Recorder> recorder, std::uint32_t id)
+    : inner_(inner), recorder_(std::move(recorder)), id_(id)
+{
+    add(static_cast<imvu::PiInternalIndexBuffer*>(this));
+}
+
+IndexBuffer::~IndexBuffer()
+{
+    remove(static_cast<imvu::PiInternalIndexBuffer*>(this));
+    delete inner_;
+    recorder_->destroyBuffer(id_);
+}
+
+VertexBuffer::VertexBuffer(imvu::PiInternalVertexBuffer* inner, std::shared_ptr<Recorder> recorder, std::uint32_t id)
+    : inner_(inner), recorder_(std::move(recorder)), id_(id)
+{
+    add(static_cast<imvu::PiInternalVertexBuffer*>(this));
+}
+
+VertexBuffer::~VertexBuffer()
+{
+    remove(static_cast<imvu::PiInternalVertexBuffer*>(this));
+    delete inner_;
+    recorder_->destroyBuffer(id_);
+}
+
+void VertexBuffer::update(const void* data, std::uint32_t stride, std::uint32_t elementSize, std::uint32_t elementCount)
+{
+    { const InnerCall timed; inner_->update(data, stride, elementSize, elementCount); }
+    recorder_->updateBuffer(id_, data, stride, elementSize, elementCount);
+}
+
+void VertexBuffer::unknown2() { inner_->unknown2(); }
+
+PixmapTarget::PixmapTarget(std::shared_ptr<Recorder> recorder, imvu::Vec2i size)
+    : recorder_(std::move(recorder)),
+      id_(recorder_->createRenderTarget(static_cast<std::uint32_t>(size.x), static_cast<std::uint32_t>(size.y))),
+      size_(size), pixmap_(size.x, size.y)
+{
+    add(static_cast<imvu::PiRenderTarget*>(this));
+}
+
+PixmapTarget::~PixmapTarget()
+{
+    remove(static_cast<imvu::PiRenderTarget*>(this));
+    recorder_->destroyTexture(id_);
+}
+
+imvu::Pixmap* PixmapTarget::getPixmap(imvu::Pixmap* result) const { return pixmap_.copyTo(result); }
+
+void PixmapTarget::setPixels(std::span<const std::byte> pixels)
+{
+    const auto into = pixmap_.valid() ? pixmap_pixels(pixmap_.get()) : std::nullopt;
+    const auto width = static_cast<std::uint32_t>(size_.x);
+    const auto height = static_cast<std::uint32_t>(size_.y);
+    const std::size_t rowSize = std::size_t{width} * 4;
+    if (!into || into->pixels == nullptr || pixels.size() < rowSize * height) {
+        log::info("render target: {}x{} frame not read back ({} bytes)", width, height, pixels.size());
+        return;
+    }
+    const std::size_t copied = std::min<std::size_t>(rowSize, std::size_t{into->width} * 4);
+    auto* rows = reinterpret_cast<std::byte*>(into->pixels);
+    for (std::uint32_t y = 0; y < std::min(into->height, height); ++y) {
+        std::memcpy(rows + std::size_t{y} * into->rowBytes, pixels.data() + y * rowSize, copied);
+    }
+}
+
+TextureTarget::TextureTarget(std::shared_ptr<Recorder> recorder, imvu::Vec2i size)
+    : recorder_(std::move(recorder)),
+      id_(recorder_->createRenderTarget(static_cast<std::uint32_t>(size.x), static_cast<std::uint32_t>(size.y))),
+      size_(size)
+{
+    add(static_cast<imvu::PiRenderTarget*>(this));
+}
+
+TextureTarget::~TextureTarget()
+{
+    remove(static_cast<imvu::PiRenderTarget*>(this));
+    recorder_->destroyTexture(id_);
+}
+
+imvu::TextureArea* TextureTarget::area(imvu::TextureArea* result) const
+{
+    return new (result) imvu::TextureArea{0, 0, 1, 1};
+}
+
+imvu::SharedPtr<imvu::PiRenderTexture>* TextureTarget::texture(imvu::SharedPtr<imvu::PiRenderTexture>* result) const
+{
+    return new (result) imvu::SharedPtr<imvu::PiRenderTexture>(
+        std::unique_ptr<imvu::PiRenderTexture>(new Texture(recorder_, id_, size_)));
+}
+
+} // namespace t5de

adapter/resources.hpp

@@ -0,0 +1,141 @@
+#pragma once
+// The textures and buffers the adapter's engine hands to the client: each wraps the client renderer's own (which the
+// client renderer still draws with) and mirrors it, by id, to the renderer process. The client deletes them through
+// their virtual destructors.
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <span>
+
+#include "pixmap.hpp"
+
+#include "recorder.hpp"
+#include "t5de/imvu/resources.hpp"
+
+namespace t5de {
+
+class Texture final : public imvu::PiRenderTexture {
+public:
+    Texture(imvu::PiRenderTexture* inner, std::shared_ptr<Recorder> recorder, std::uint32_t id);
+    // What's been drawn into one of our texture render targets (TextureTarget): no texture of the client renderer's,
+    // and the id stays the target's.
+    Texture(std::shared_ptr<Recorder> recorder, std::uint32_t targetId, imvu::Vec2i size);
+    ~Texture() override;
+
+    imvu::Vec2i size() const override;
+    void updateRegions(const imvu::Pixmap& pixmap, const imvu::CompoundRegion& regions) override;
+    void update(const imvu::Pixmap& pixmap) override;
+    imvu::Pixmap* read(imvu::Pixmap* result) const override;
+
+    [[nodiscard]] imvu::PiRenderTexture* inner() const { return inner_; }
+    [[nodiscard]] std::uint32_t id() const { return id_; }
+
+private:
+    imvu::PiRenderTexture* inner_;
+    std::shared_ptr<Recorder> recorder_;
+    std::uint32_t id_;
+    imvu::Vec2i size_{};
+    bool ownsId_ = true;
+};
+
+// Render targets the renderer process draws (made while it runs; otherwise the client renderer makes its own).
+class PixmapTarget final : public imvu::PiPixmapRenderTarget {
+public:
+    PixmapTarget(std::shared_ptr<Recorder> recorder, imvu::Vec2i size);
+    ~PixmapTarget() override;
+
+    imvu::Pixmap* getPixmap(imvu::Pixmap* result) const override;
+
+    // Copies a frame's pixels, read back from the renderer process (rows packed, 0xAARRGGBB), into the pixmap.
+    void setPixels(std::span<const std::byte> pixels);
+
+    [[nodiscard]] std::uint32_t id() const { return id_; }
+
+private:
+    std::shared_ptr<Recorder> recorder_;
+    std::uint32_t id_;
+    imvu::Vec2i size_;
+    OwnedPixmap pixmap_;
+};
+
+class TextureTarget final : public imvu::PiTextureRenderTarget {
+public:
+    TextureTarget(std::shared_ptr<Recorder> recorder, imvu::Vec2i size);
+    ~TextureTarget() override;
+
+    imvu::TextureArea* area(imvu::TextureArea* result) const override;
+    imvu::SharedPtr<imvu::PiRenderTexture>* texture(imvu::SharedPtr<imvu::PiRenderTexture>* result) const override;
+
+    [[nodiscard]] std::uint32_t id() const { return id_; }
+
+private:
+    std::shared_ptr<Recorder> recorder_;
+    std::uint32_t id_;
+    imvu::Vec2i size_;
+};
+
+class IndexBuffer final : public imvu::PiInternalIndexBuffer {
+public:
+    IndexBuffer(imvu::PiInternalIndexBuffer* inner, std::shared_ptr<Recorder> recorder, std::uint32_t id);
+    ~IndexBuffer() override;
+
+    [[nodiscard]] imvu::PiInternalIndexBuffer* inner() const { return inner_; }
+    [[nodiscard]] std::uint32_t id() const { return id_; }
+
+private:
+    imvu::PiInternalIndexBuffer* inner_;
+    std::shared_ptr<Recorder> recorder_;
+    std::uint32_t id_;
+};
+
+class VertexBuffer final : public imvu::PiInternalVertexBuffer {
+public:
+    VertexBuffer(imvu::PiInternalVertexBuffer* inner, std::shared_ptr<Recorder> recorder, std::uint32_t id);
+    ~VertexBuffer() override;
+
+    void update(const void* data, std::uint32_t stride, std::uint32_t elementSize,
+                std::uint32_t elementCount) override;
+    void unknown2() override;
+
+    [[nodiscard]] imvu::PiInternalVertexBuffer* inner() const { return inner_; }
+    [[nodiscard]] std::uint32_t id() const { return id_; }
+
+private:
+    imvu::PiInternalVertexBuffer* inner_;
+    std::shared_ptr<Recorder> recorder_;
+    std::uint32_t id_;
+};
+
+// Whether an object is one of ours (live Texture, IndexBuffer, VertexBuffer, PixmapTarget or TextureTarget): the client
+// can also hand the engine objects the client renderer made itself (its render targets, and their textures), which
+// must reach it unchanged.
+bool ours(const void* object);
+
+// The client renderer's object, and our id, for what the client passes in: ours unwrapped, others unchanged (id 0).
+inline imvu::PiRenderTexture* inner(imvu::PiRenderTexture* texture)
+{
+    return ours(texture) ? static_cast<Texture*>(texture)->inner() : texture;
+}
+inline std::uint32_t id(imvu::PiRenderTexture* texture)
+{
+    return ours(texture) ? static_cast<Texture*>(texture)->id() : 0;
+}
+inline imvu::PiInternalIndexBuffer* inner(imvu::PiInternalIndexBuffer* buffer)
+{
+    return ours(buffer) ? static_cast<IndexBuffer*>(buffer)->inner() : buffer;
+}
+inline std::uint32_t id(imvu::PiInternalIndexBuffer* buffer)
+{
+    return ours(buffer) ? static_cast<IndexBuffer*>(buffer)->id() : 0;
+}
+inline imvu::PiInternalVertexBuffer* inner(imvu::PiInternalVertexBuffer* buffer)
+{
+    return ours(buffer) ? static_cast<VertexBuffer*>(buffer)->inner() : buffer;
+}
+inline std::uint32_t id(imvu::PiInternalVertexBuffer* buffer)
+{
+    return ours(buffer) ? static_cast<VertexBuffer*>(buffer)->id() : 0;
+}
+
+} // namespace t5de

adapter/scene_hooks.cpp

@@ -0,0 +1,503 @@
+#include "scene_hooks.hpp"
+
+#include <windows.h>
+
+#include <algorithm>
+#include <atomic>
+#include <cmath>
+#include <cstring>
+#include <mutex>
+#include <unordered_map>
+
+#include "log.hpp"
+
+namespace t5de::scene_hooks {
+
+namespace {
+
+// IMVU's SceneViewer::step() and ModelInstance::updateCalSkeleton(): methods, called with the object in ECX.
+using Method = void(__thiscall*)(void* self);
+
+Method originalStep = nullptr;
+Method originalUpdateCalSkeleton = nullptr;
+// IMVU's CameraController::getCameraTransform(): returns a Transform by value (constructed in result).
+using GetTransform = void*(__thiscall*)(const void* self, void* result);
+GetTransform originalGetCameraTransform = nullptr;
+float cameraEasing = 0; // the share of the way to its target the camera moves at each tick
+std::atomic<std::int64_t> stepTime = 0;
+std::atomic<std::uint64_t> steps = 0;
+// How many ticks the last step covered: the client steps a scene several ticks at once when it falls behind.
+std::atomic<int> stepTicks = 1;
+std::atomic<bool> stepHooked = false;
+std::atomic<bool> poseHooked = false;
+bool crossfades = false; // whether ModelInstance::step's crossfades are as expected (checked when installing)
+std::atomic<bool> cameraHooked = false;
+std::atomic<bool> particlesHooked = false;
+
+// IMVU's ParticleSystem::render(RenderManager*, const Transform&, const Transform&): a method with 3 arguments.
+using RenderParticles = void(__thiscall*)(void* self, void* renderManager, const void* a, const void* b);
+RenderParticles originalRenderParticles = nullptr;
+// The particle library's (ParticleLib.dll: PAPI, the Particle System API) PContextParticleGroup_t::GetParticlePointer:
+// the current group's particles, as floats: returns their count, and sets the first's address, the stride between
+// them, and the offsets of their attributes (in floats): position, previous position, size, velocity, previous
+// velocity, color, alpha, age, up, rotational velocity, previous up, mass, data.
+using GetParticlePointer = unsigned(__thiscall*)(void* group, float*& particles, unsigned& stride, unsigned& position,
+                                                 unsigned& positionB, unsigned& size, unsigned& velocity,
+                                                 unsigned& velocityB, unsigned& color, unsigned& alpha, unsigned& age,
+                                                 unsigned& up, unsigned& rotationalVelocity, unsigned& upB,
+                                                 unsigned& mass, unsigned& data);
+GetParticlePointer getParticlePointer = nullptr;
+// PContextParticleGroup_t::GetGroupCount: how many particle groups there are (GetParticlePointer throws without one).
+using GetGroupCount = unsigned(__thiscall*)(void* group);
+GetGroupCount getGroupCount = nullptr;
+
+// zero.dll's constants: a tick, in milliseconds (33), and an animation frame, in seconds (1/30).
+const unsigned* millisecondsPerFrame = nullptr;
+const float* secondsPerFrame = nullptr;
+
+LARGE_INTEGER frequency()
+{
+    static const LARGE_INTEGER value = [] {
+        LARGE_INTEGER f;
+        QueryPerformanceFrequency(&f);
+        return f;
+    }();
+    return value;
+}
+
+// Our SceneViewer::step: records the tick, then steps as IMVU's does. __fastcall takes ECX like __thiscall (EDX unused).
+// Each scene viewer steps in turn at a tick: steps closer than 5 ms are the same tick.
+void __fastcall step(void* self, void* /*edx*/)
+{
+    LARGE_INTEGER now;
+    QueryPerformanceCounter(&now);
+    const std::int64_t last = stepTime.load();
+    if (now.QuadPart - last > frequency().QuadPart / 200) {
+        ++steps;
+        if (last != 0 && millisecondsPerFrame != nullptr && *millisecondsPerFrame != 0) {
+            const double ticks = static_cast<double>(now.QuadPart - last) * 1000.0 /
+                                 static_cast<double>(frequency().QuadPart) / *millisecondsPerFrame;
+            stepTicks = std::clamp(static_cast<int>(ticks + 0.5), 1, 5);
+        }
+        stepTime = now.QuadPart;
+    }
+    originalStep(self);
+}
+
+// IMVU's objects, as far as posing between ticks reads and writes them (from SceneWindow.dll's ModelInstance::step,
+// which copies each effect's time and weight into its Cal3D animation at every tick, and updateCalSkeleton):
+// - ModelInstance: +0x2c, a flag: its skeleton must be posed again; +0x120, its animation effects, a std::list (a pointer
+//   to the list's head node; a node: next, previous, then the effect).
+// - Effect: +0x34, playing (a flag); +0x3c, its time, in seconds; +0x90, its Cal3D animation.
+// - The Cal3D animation: +0x8, its time, which the mixer poses the skeleton at (CalMixer::updateSkeleton); +0xc, its
+//   weight in the pose.
+//
+// Crossfades (ModelInstance::step, at each tick): an effect fading in (+0x44 set, +0x18 nonzero) has its weight
+// (+0x38) ramped over 10 ticks, counted at +0x48: (n + 1) * 0.1 * weight, then n goes up. One fading out is in the
+// model's crossfade list (+0x138, a std::list; a node holds the effect at +0xc and its count at +0x14): m goes up, then
+// (1 - m * 0.1) * weight; after 10, it's removed. Between ticks, both are partway to the next tick's weight.
+constexpr std::size_t modelPoseDirty = 0x2c;
+constexpr std::size_t modelEffects = 0x120;
+constexpr std::size_t modelFadingOut = 0x138;
+constexpr std::size_t effectPlaying = 0x34;
+constexpr std::size_t effectTime = 0x3c;
+constexpr std::size_t effectAnimation = 0x90;
+constexpr std::size_t effectFadesIn = 0x44;
+constexpr std::size_t effectFadeSource = 0x18;
+constexpr std::size_t effectFadeCount = 0x48;
+constexpr std::size_t effectWeight = 0x38;
+constexpr std::size_t fadingOutEffect = 0xc;
+constexpr std::size_t fadingOutCount = 0x14;
+constexpr std::size_t animationTime = 0x8;
+constexpr std::size_t animationWeight = 0xc;
+constexpr unsigned fadeTicks = 10;
+
+template <class T>
+T& field(void* object, std::size_t offset)
+{
+    return *reinterpret_cast<T*>(static_cast<std::byte*>(object) + offset);
+}
+
+// Each effect's time at the last two ticks it was posed at, to tell an animation playing on (at any rate: the time it
+// moved per tick at the last step) from one held, looping back or just started (posed as it is).
+struct EffectHistory {
+    std::uint64_t step = 0;
+    float time = 0;
+    float previous = -1;
+};
+std::unordered_map<void*, EffectHistory> histories;
+
+// How far into the current tick the client is, from 0 to just under 1; 0 if unknown.
+float tick_fraction()
+{
+    const std::int64_t last = stepTime.load();
+    if (last == 0 || millisecondsPerFrame == nullptr || *millisecondsPerFrame == 0) {
+        return 0;
+    }
+    LARGE_INTEGER now;
+    QueryPerformanceCounter(&now);
+    const double elapsed = static_cast<double>(now.QuadPart - last) * 1000.0 / static_cast<double>(frequency().QuadPart);
+    return static_cast<float>(std::clamp(elapsed / *millisecondsPerFrame, 0.0, 0.999));
+}
+
+// Our ModelInstance::updateCalSkeleton, called where ModelInstance::render poses the model before drawing it: between
+// ticks, poses it at the time between them. Each playing animation that moved on at the last step is set ahead by the
+// fraction of a tick since, at the rate it moved (up to 4 frames a tick), and crossfading animations' weights partway
+// to the next tick's; the skeleton is posed (by IMVU's), and the times and weights put back, with the skeleton marked to
+// be posed again, so everything else sees the tick's pose.
+void __fastcall updateCalSkeleton(void* model, void* /*edx*/)
+{
+    const float fraction = tick_fraction();
+    if (fraction < 0.01f || secondsPerFrame == nullptr) {
+        originalUpdateCalSkeleton(model);
+        return;
+    }
+    const std::uint64_t tick = steps.load();
+    const float frame = *secondsPerFrame;
+
+    struct Saved {
+        float* value;
+        float was;
+    };
+    Saved saved[128];
+    std::size_t count = 0;
+    const auto set = [&](float& value, float to) {
+        saved[count++] = {&value, value};
+        value = to;
+    };
+    void* head = field<void*>(model, modelEffects);
+    for (void* node = head != nullptr ? field<void*>(head, 0) : nullptr; node != nullptr && node != head && count < 126;
+         node = field<void*>(node, 0)) {
+        void* effect = field<void*>(node, 8);
+        void* animation = effect != nullptr ? field<void*>(effect, effectAnimation) : nullptr;
+        if (animation == nullptr) {
+            continue;
+        }
+        const unsigned faded = field<std::uint32_t>(effect, effectFadeCount);
+        if (crossfades && field<std::uint8_t>(effect, effectFadesIn) != 0 && field<std::int32_t>(effect, effectFadeSource) != 0
+            && faded >= 1 && faded < fadeTicks) {
+            set(field<float>(animation, animationWeight),
+                (static_cast<float>(faded) + fraction) * 0.1f * field<float>(effect, effectWeight));
+        }
+        if (field<std::uint8_t>(effect, effectPlaying) == 0) {
+            continue;
+        }
+        const float time = field<float>(effect, effectTime);
+        EffectHistory& history = histories[effect];
+        if (history.step != tick) {
+            history.previous = history.step + 1 == tick ? history.time : -1;
+            history.time = time;
+            history.step = tick;
+        }
+        const float perTick = (history.time - history.previous) / static_cast<float>(stepTicks.load());
+        if (history.previous < 0 || perTick <= frame * 0.01f || perTick > frame * 4) {
+            continue; // held, looped back, or just started: as it is
+        }
+        set(field<float>(animation, animationTime), time + fraction * perTick);
+    }
+    void* fadingHead = crossfades ? field<void*>(model, modelFadingOut) : nullptr;
+    for (void* node = fadingHead != nullptr ? field<void*>(fadingHead, 0) : nullptr;
+         node != nullptr && node != fadingHead && count < 127; node = field<void*>(node, 0)) {
+        void* effect = field<void*>(node, fadingOutEffect);
+        void* animation = effect != nullptr ? field<void*>(effect, effectAnimation) : nullptr;
+        const unsigned faded = field<std::uint32_t>(node, fadingOutCount);
+        if (animation != nullptr && faded >= 1 && faded < fadeTicks) {
+            set(field<float>(animation, animationWeight),
+                (1.0f - (static_cast<float>(faded) + fraction) * 0.1f) * field<float>(effect, effectWeight));
+        }
+    }
+    if (count == 0) {
+        originalUpdateCalSkeleton(model);
+        return;
+    }
+    field<std::uint8_t>(model, modelPoseDirty) = 1;
+    originalUpdateCalSkeleton(model);
+    for (std::size_t i = count; i-- > 0;) {
+        *saved[i].value = saved[i].was;
+    }
+    field<std::uint8_t>(model, modelPoseDirty) = 1;
+
+    // Forget effects not posed for a while (they may be gone).
+    if (histories.size() > 1024) {
+        std::erase_if(histories, [tick](const auto& entry) { return entry.second.step + 30 < tick; });
+    }
+}
+
+// The camera (SceneWindow.dll's CameraController::step, at each tick): each of these values moves a share k of the way
+// to its target (k is 0.4): the camera's position (+0x118, 3 floats, to +0xf0; panning moves the target), and its
+// orbit angles and zoom, in degrees (+0x140, 3 floats, to +0x134; the difference taken between -180 and 180).
+// A fraction f of a tick on, the same easing has moved it 1 - (1 - k)^f of the way: exactly, nothing guessed. The point
+// the camera looks at (+0x160, 3 floats) is the position plus an offset (setCameraFocus, at each tick), so it moves with
+// the position.
+constexpr std::size_t cameraPosition = 0x118;
+constexpr std::size_t cameraPositionTarget = 0xf0;
+constexpr std::size_t cameraAngles = 0x140;
+constexpr std::size_t cameraAnglesTarget = 0x134;
+constexpr std::size_t cameraFocus = 0x160;
+// Nonzero: the camera shows a fixed view ("take"), not eased.
+constexpr std::size_t cameraTake = 0xec;
+
+float degrees180(float degrees)
+{
+    float wrapped = std::fmod(degrees + 180.0f, 360.0f);
+    if (wrapped < 0) {
+        wrapped += 360.0f;
+    }
+    return wrapped - 180.0f;
+}
+
+// Our CameraController::getCameraTransform: between ticks, the camera where its easing has brought it since the tick.
+// The eased values are set ahead for IMVU's code to make the transform from, then put back. __fastcall takes ECX like
+// __thiscall, and like it the callee pops the stack argument.
+void* __fastcall getCameraTransform(void* camera, void* /*edx*/, void* result)
+{
+    const float fraction = tick_fraction();
+    if (fraction < 0.01f || field<std::int32_t>(camera, cameraTake) != 0) {
+        return originalGetCameraTransform(camera, result);
+    }
+    const float moved = 1.0f - std::pow(1.0f - cameraEasing, fraction);
+    float saved[9];
+    for (int i = 0; i < 3; ++i) {
+        float& position = field<float>(camera, cameraPosition + i * 4);
+        float& focus = field<float>(camera, cameraFocus + i * 4);
+        saved[i] = position;
+        saved[6 + i] = focus;
+        const float step = (field<float>(camera, cameraPositionTarget + i * 4) - position) * moved;
+        position += step;
+        focus += step;
+        float& angle = field<float>(camera, cameraAngles + i * 4);
+        saved[3 + i] = angle;
+        angle = degrees180(angle + degrees180(field<float>(camera, cameraAnglesTarget + i * 4) - angle) * moved);
+    }
+    void* transform = originalGetCameraTransform(camera, result);
+    for (int i = 0; i < 3; ++i) {
+        field<float>(camera, cameraPosition + i * 4) = saved[i];
+        field<float>(camera, cameraAngles + i * 4) = saved[3 + i];
+        field<float>(camera, cameraFocus + i * 4) = saved[6 + i];
+    }
+    return transform;
+}
+
+// Particles (SceneWindow.dll's ParticleSystem::step, at each tick) move by their velocity times the tick's time
+// (PContextActionList_t::TimeStep, millisecondsPerFrame / 1000 seconds a tick, then Move). Between ticks, they're drawn
+// moved on by their velocity times the time since the tick, then moved back the same way. (ParticleSystem::render
+// sorts the particles by distance before drawing them, reordering them in memory: each is moved back by its own
+// velocity, wherever it now is.) A ParticleSystem's particle group is at +0x28 (what ParticleSystem::render reads
+// them from).
+constexpr std::size_t particleGroup = 0x28;
+
+void __fastcall renderParticles(void* system, void* /*edx*/, void* renderManager, const void* a, const void* b)
+{
+    const float fraction = tick_fraction();
+    void* group = static_cast<std::byte*>(system) + particleGroup;
+    float* particles = nullptr;
+    unsigned stride = 0, position = 0, positionB = 0, size = 0, velocity = 0, velocityB = 0, color = 0, alpha = 0,
+             age = 0, up = 0, rotationalVelocity = 0, upB = 0, mass = 0, data = 0;
+    // As ParticleSystem::render does: no particles without a group. The library reports errors by throwing; then the
+    // particles are drawn as they are.
+    const auto particle_pointer = [&] {
+        try {
+            if (getGroupCount(group) != 0) {
+                return getParticlePointer(group, particles, stride, position, positionB, size, velocity, velocityB,
+                                          color, alpha, age, up, rotationalVelocity, upB, mass, data);
+            }
+        } catch (...) {
+        }
+        return 0u;
+    };
+    const unsigned count = fraction >= 0.01f ? particle_pointer() : 0;
+    if (count == 0 || particles == nullptr || stride == 0) {
+        originalRenderParticles(system, renderManager, a, b);
+        return;
+    }
+    const float seconds = fraction * static_cast<float>(*millisecondsPerFrame) / 1000.0f;
+    const auto move = [&](float by) {
+        for (unsigned i = 0; i < count; ++i) {
+            float* particle = particles + std::size_t{i} * stride;
+            for (unsigned axis = 0; axis < 3; ++axis) {
+                particle[position + axis] += particle[velocity + axis] * by;
+            }
+        }
+    };
+    move(seconds);
+    originalRenderParticles(system, renderManager, a, b);
+    if (particle_pointer() == count && particles != nullptr) { // the same particles, maybe reordered
+        move(-seconds);
+    }
+}
+
+// Replaces the vtable entry at slot, if it holds expected; returns whether it did.
+bool replace(void** slot, void* expected, void* replacement)
+{
+    if (*slot != expected) {
+        return false;
+    }
+    DWORD protection = 0;
+    if (!VirtualProtect(slot, sizeof(void*), PAGE_READWRITE, &protection)) {
+        return false;
+    }
+    *slot = replacement;
+    VirtualProtect(slot, sizeof(void*), protection, &protection);
+    FlushInstructionCache(GetCurrentProcess(), slot, sizeof(void*));
+    return true;
+}
+
+// Redirects the call instruction (E8, then the target relative to the next instruction) at site, if it calls
+// expected; returns whether it did.
+bool redirect_call(std::byte* site, void* expected, void* replacement)
+{
+    std::int32_t offset = 0;
+    std::memcpy(&offset, site + 1, sizeof(offset));
+    if (site[0] != std::byte{0xe8} || site + 5 + offset != expected) {
+        return false;
+    }
+    const auto replacementOffset = static_cast<std::int32_t>(static_cast<std::byte*>(replacement) - (site + 5));
+    DWORD protection = 0;
+    if (!VirtualProtect(site, 5, PAGE_EXECUTE_READWRITE, &protection)) {
+        return false;
+    }
+    std::memcpy(site + 1, &replacementOffset, sizeof(replacementOffset));
+    VirtualProtect(site, 5, protection, &protection);
+    FlushInstructionCache(GetCurrentProcess(), site, 5);
+    return true;
+}
+
+void install_step(HMODULE sceneWindow)
+{
+    auto* vtable = reinterpret_cast<void**>(GetProcAddress(sceneWindow, "??_7SceneViewer@@6BIFrameListener@@@"));
+    auto* stepMethod = GetProcAddress(sceneWindow, "?step@SceneViewer@@UAEXXZ");
+    // IFrameListener's vtable: its destructor, then step (what stepFrame calls).
+    if (vtable == nullptr || stepMethod == nullptr) {
+        log::info("scene hooks: SceneViewer's vtable or step not found");
+        return;
+    }
+    originalStep = reinterpret_cast<Method>(stepMethod);
+    if (!replace(&vtable[1], reinterpret_cast<void*>(stepMethod), reinterpret_cast<void*>(&step))) {
+        log::info("scene hooks: SceneViewer's vtable doesn't hold its step");
+        return;
+    }
+    stepHooked = true;
+}
+
+void install_pose(HMODULE sceneWindow)
+{
+    HMODULE zero = GetModuleHandleW(L"zero.dll");
+    millisecondsPerFrame =
+        zero == nullptr ? nullptr : reinterpret_cast<const unsigned*>(GetProcAddress(zero, "?millisecondsPerFrame@@3IB"));
+    secondsPerFrame = zero == nullptr ? nullptr : reinterpret_cast<const float*>(GetProcAddress(zero, "?secondsPerFrame@@3MB"));
+    auto* render = reinterpret_cast<std::byte*>(GetProcAddress(
+        sceneWindow, "?render@ModelInstance@@QAEXPAVRenderManager@@ABVCullingFrustum@@ABVTransform@@2ABUFogState@@"
+                     "ABULightState@@_NAAVSceneStats@@ABVRenderSettings@@@Z"));
+    auto* update = GetProcAddress(sceneWindow, "?updateCalSkeleton@ModelInstance@@AAEXXZ");
+    if (millisecondsPerFrame == nullptr || secondsPerFrame == nullptr || render == nullptr || update == nullptr) {
+        log::info("scene hooks: ModelInstance::render, updateCalSkeleton or zero.dll's frame lengths not found");
+        return;
+    }
+    // ModelInstance::render poses the model first: its 5th instruction, at +0x12, calls updateCalSkeleton.
+    originalUpdateCalSkeleton = reinterpret_cast<Method>(update);
+    if (!redirect_call(render + 0x12, reinterpret_cast<void*>(update), reinterpret_cast<void*>(&updateCalSkeleton))) {
+        log::info("scene hooks: ModelInstance::render doesn't call updateCalSkeleton where expected");
+        return;
+    }
+    poseHooked = true;
+
+    // Crossfades: ModelInstance::step's instructions that count a fade in (cmp dword ptr [eax + 0x48], 10) and a fade
+    // out (cmp dword ptr [ebx + 0x14], 10), where expected.
+    auto* step = reinterpret_cast<const std::byte*>(GetProcAddress(sceneWindow, "?step@ModelInstance@@QAEXABVFrameInterval@@@Z"));
+    constexpr std::uint8_t fadeIn[] = {0x83, 0x78, 0x48, 0x0a};
+    constexpr std::uint8_t fadeOut[] = {0x83, 0x7b, 0x14, 0x0a};
+    crossfades = step != nullptr && std::memcmp(step + 0xc6, fadeIn, sizeof(fadeIn)) == 0
+                 && std::memcmp(step + 0xf1, fadeOut, sizeof(fadeOut)) == 0;
+    if (!crossfades) {
+        log::info("scene hooks: ModelInstance::step's crossfades not as expected; crossfades at the client's rate");
+    }
+}
+
+void install_particles(HMODULE sceneWindow)
+{
+    HMODULE particleLib = GetModuleHandleW(L"ParticleLib.dll");
+    getParticlePointer = particleLib == nullptr
+                             ? nullptr
+                             : reinterpret_cast<GetParticlePointer>(GetProcAddress(
+                                   particleLib, "?GetParticlePointer@PContextParticleGroup_t@PAPI@@QAEIAAPAMAAI1111111111111@Z"));
+    getGroupCount = particleLib == nullptr ? nullptr
+                                           : reinterpret_cast<GetGroupCount>(GetProcAddress(
+                                                 particleLib, "?GetGroupCount@PContextParticleGroup_t@PAPI@@QAEIXZ"));
+    auto* modelRender = reinterpret_cast<std::byte*>(GetProcAddress(
+        sceneWindow, "?render@ModelInstance@@QAEXPAVRenderManager@@ABVCullingFrustum@@ABVTransform@@2ABUFogState@@"
+                     "ABULightState@@_NAAVSceneStats@@ABVRenderSettings@@@Z"));
+    auto* render = GetProcAddress(sceneWindow, "?render@ParticleSystem@@QAEXPAVRenderManager@@ABVTransform@@1@Z");
+    if (getParticlePointer == nullptr || getGroupCount == nullptr || modelRender == nullptr || render == nullptr
+        || millisecondsPerFrame == nullptr) {
+        log::info("scene hooks: ParticleLib's GetParticlePointer, ModelInstance::render or ParticleSystem::render not found");
+        return;
+    }
+    // ModelInstance::render draws its particle systems with a call at +0x114.
+    originalRenderParticles = reinterpret_cast<RenderParticles>(render);
+    if (!redirect_call(modelRender + 0x114, reinterpret_cast<void*>(render), reinterpret_cast<void*>(&renderParticles))) {
+        log::info("scene hooks: ModelInstance::render doesn't call ParticleSystem::render where expected");
+        return;
+    }
+    particlesHooked = true;
+}
+
+void install_camera(HMODULE sceneWindow)
+{
+    auto* vtable = reinterpret_cast<void**>(GetProcAddress(sceneWindow, "??_7CameraController@@6B@"));
+    auto* get = GetProcAddress(sceneWindow, "?getCameraTransform@CameraController@@UBE?AVTransform@@XZ");
+    auto* step = reinterpret_cast<const std::byte*>(GetProcAddress(sceneWindow, "?step@CameraController@@UAEXXZ"));
+    if (vtable == nullptr || get == nullptr || step == nullptr) {
+        log::info("scene hooks: CameraController's vtable, getCameraTransform or step not found");
+        return;
+    }
+    // The easing share: a float constant CameraController::step reads (at SceneWindow.dll's 0x100cb934 when loaded at
+    // its preferred address), checked to be referenced by step's code and to be the expected 0.4.
+    const auto* base = reinterpret_cast<const std::byte*>(sceneWindow);
+    const auto* easing = reinterpret_cast<const float*>(base + 0xcb934);
+    const auto address = static_cast<std::uint32_t>(reinterpret_cast<std::uintptr_t>(easing));
+    bool referenced = false;
+    for (std::size_t i = 0; i + 4 <= 0x700 && !referenced; ++i) {
+        referenced = std::memcmp(step + i, &address, 4) == 0;
+    }
+    if (!referenced || *easing != 0.4f) {
+        log::info("scene hooks: CameraController::step's easing not where expected");
+        return;
+    }
+    cameraEasing = *easing;
+    // CameraController's vtable: getCameraTransform is its 6th entry.
+    originalGetCameraTransform = reinterpret_cast<GetTransform>(get);
+    if (!replace(&vtable[5], reinterpret_cast<void*>(get), reinterpret_cast<void*>(&getCameraTransform))) {
+        log::info("scene hooks: CameraController's vtable doesn't hold its getCameraTransform");
+        return;
+    }
+    cameraHooked = true;
+}
+
+} // namespace
+
+void install()
+{
+    static std::once_flag once;
+    std::call_once(once, [] {
+        HMODULE sceneWindow = GetModuleHandleW(L"SceneWindow.dll");
+        if (sceneWindow == nullptr) {
+            log::info("scene hooks: SceneWindow.dll not loaded");
+            return;
+        }
+        install_step(sceneWindow);
+        if (stepHooked) { // drawing between ticks needs the ticks
+            install_pose(sceneWindow);
+            install_particles(sceneWindow);
+            install_camera(sceneWindow);
+        }
+        log::info("scene hooks: ticks {}, posing between ticks {}, particles between ticks {}, camera between ticks {}",
+                  stepHooked ? "recorded" : "not recorded", poseHooked ? "on" : "off", particlesHooked ? "on" : "off",
+                  cameraHooked ? "on" : "off");
+    });
+}
+
+bool installed() { return stepHooked; }
+
+std::int64_t lastStep() { return stepTime; }
+
+} // namespace t5de::scene_hooks

adapter/scene_hooks.hpp

@@ -0,0 +1,30 @@
+#pragma once
+// Our hooks into SceneWindow.dll's scene code, installed once, the first time an engine is made. Each replaces where
+// IMVU's code calls a function (an entry of an exported vtable, or a call instruction's target), after checking it
+// calls the function expected, with ours, which calls IMVU's: nothing else is changed, and nothing is if a check
+// fails (an unexpected SceneWindow.dll: the hooks' features are then off, and the client runs as it would without).
+//
+// - SceneViewer::step (the IFrameListener vtable): the client's tick, 30 times a second (SceneWindow.dll's runApp
+//   calls stepFrame, which steps each scene viewer). Recorded, for the frame pacer and for drawing between ticks.
+// - ModelInstance::render's call to updateCalSkeleton, which poses the model before it's drawn: between ticks, the
+//   model is posed at the time between them (its animations' times moved on by the fraction of a frame since the
+//   tick; Cal3D poses between keyframes) and crossfading animations' weights partway to the next tick's, then its
+//   animations are put back as they were.
+// - ModelInstance::render's call to ParticleSystem::render: between ticks, particles drawn moved on by their velocity
+//   times the time since the tick (as the particle library moves them at each tick), then put back.
+// - CameraController::getCameraTransform (its exported vtable): between ticks, the camera where its easing toward its
+//   target has brought it since the tick.
+
+#include <cstdint>
+
+namespace t5de::scene_hooks {
+
+void install();
+
+// Whether the hooks are installed.
+[[nodiscard]] bool installed();
+
+// When a scene viewer last stepped (QueryPerformanceCounter), or 0 if none has.
+[[nodiscard]] std::int64_t lastStep();
+
+} // namespace t5de::scene_hooks

docs/architecture.md

@@ -0,0 +1,111 @@
+# Architecture
+
+The renderer is two programs:
+
+- **The adapter**, `t5deRenderEngine.dll` (32-bit, `adapter/`): a renderer plugin IMVU Classic loads in place of its
+  OpenGL renderer (selected by the `t5de-renderer` patch in the `t5de` repository). It implements IMVU's
+  `PiRenderEngine` interface (`include/t5de/imvu/`, `docs/interface.md`) and passes what the client draws to the
+  renderer process. It stays thin: IMVU's process is 32-bit (4 GB of address space shared with Python, Gecko and
+  IMVU's own code) and tied to Visual C++ 2010's ABI.
+- **The renderer process**, `t5de-renderer.exe` (64-bit, `renderer/`): draws, with
+  [Diligent Engine](https://github.com/DiligentGraphics/DiligentCore) (Apache-2.0). Being 64-bit and separate, it can
+  use any modern API and library, isn't limited by the client's address space, and can crash without taking the
+  client down.
+
+Why Diligent: one API over Direct3D 11 (every Windows PC, and software rendering on machines without a graphics
+driver), Direct3D 12 and Vulkan (ray tracing, mesh shaders), and WebGPU (browsers, for a possible future client).
+It's built with CMake and fetched by `FetchContent`, pinned to a commit (`renderer/CMakeLists.txt`); only the
+Direct3D 11 backend is built for now.
+
+## How they talk
+
+`include/t5de/protocol/` is shared by both builds, so it uses fixed-size fields only. One renderer process draws all
+of a client's 3D views, with one Direct3D device. The adapter starts `t5de-renderer.exe --control <name> --parent
+<pid>` from its own folder with the first engine (again with the next one if it has exited), and creates a control
+section (`Local\t5de-renderer-<pid>`, `protocol::Control`). For each engine the client creates (each 3D view: Home's
+avatar, the room, ...), the adapter:
+
+1. creates a shared memory channel (`<control name>-<n>`) holding IMVU's window handle, and its events;
+2. counts it in the control section and sets `<control name>-attach`, and the renderer process opens it, with a
+   child window, swap chain and scene of its own;
+3. sends each frame's commands through it, and sets `closing` when the engine is destroyed (the renderer process
+   then closes the view).
+
+The renderer process draws into a child window it creates inside the client's window: window handles are valid in
+every process, and Windows allows child windows across processes (Chrome's GPU process works this way). The child
+is disabled so mouse input goes to the client's window under it. Its swap chain is a flip model one, which the
+compositor shows above the client's own drawing. The client's window must not clip its children (`WS_CLIPCHILDREN`,
+which the client creates it with, so the adapter clears it):
+the client draws a frame when its window gets `WM_PAINT` (`SceneWindow.dll` invalidates it, and draws on the paint),
+and a window entirely covered by clipped children never gets one, so the client fell to about one frame a second.
+The process exits when the client exits.
+
+## Status
+
+The renderer process draws the whole 3D view in place of the client's renderer (the full view, the default). The
+adapter still forwards state and resources to the client's Direct3D renderer (as a fallback, and for reading textures
+back, which the renderer process doesn't do), but while the renderer process covers the whole view
+(`Channel::covering`, set after each frame it presents) the client's renderer skips its clears and draws, decided per
+frame; it draws again as soon as the renderer process stops covering the view (the view changes, or the process
+fails). Checked in rooms with screenshots of both renderers side by side (the compare view): they match, particles
+and the 2D overlay (name tags) included.
+
+For comparing while the client runs (development):
+
+- Views: `T5DE_RENDERER_VIEW` (off, split, full (the default) or compare) when the client starts, or
+  `%TEMP%\t5de-renderer-view.txt` holding one of those at any time. Compare draws the left half's scene over the
+  right half, so both renderers show the same thing side by side.
+- `%TEMP%\t5de-renderer-shaders\fixed_function.hlsl`, if present, replaces the built-in shaders and is reloaded
+  when it changes.
+- The renderer process runs from a copy (`%TEMP%\t5de-renderer`), so `t5de-renderer.exe` can be replaced while the
+  client runs; engines started afterwards run the new one (the room's view keeps its engine until the client
+  restarts).
+- The adapter's log (`%TEMP%\t5de-renderer.log`) sums up what the client draws every 300 frames (the first few
+  times), and logs textures and render targets the client renderer made itself.
+
+- The command stream (`include/t5de/protocol/commands.hpp`) carries state, transforms, lights, fog, textures,
+  buffers (copied when created or updated) and draws, in chunks through the channel; the adapter waits for each to
+  be taken, and gives up on a renderer process that stops taking them (the client's renderer carries on).
+- The renderer process reproduces IMVU's Direct3D 9 setup (`renderer/shaders/fixed_function.hlsl`), particles
+  included (point sprites, drawn as instanced squares), with a pipeline per combination of states.
+- Speed: on a PC with a graphics card, drawing the whole view (3440x1059, a room of some 220 draws) takes 1.3 to
+  3.8 ms a frame, and the time from the client finishing a frame to ours being presented is the same (frames don't
+  queue, none skipped). Earlier, in the split view, the halves couldn't be told apart, even while the camera moved. On the development VM (software rendering, over Remote Desktop) drawing takes 8 to 60 ms, and
+  the right half visibly trails, mostly from compositing another process's window over Remote Desktop. The
+  renderer process draws only the newest frame when it falls behind, and keeps at most one frame queued.
+
+Render targets are the renderer process's too, while it runs: the adapter makes its own (`PixmapTarget`,
+`TextureTarget`), the renderer process draws frames into them (textures in the window's formats, so the same
+pipelines draw both), and a pixmap target's frame is read back through the channel (`Channel::readSize`, the
+`-read` event) into its Pixmap, as the client's renderer does, synchronously. A read back must fit in the channel's
+data area (16 MB: the client's 2048x2048 snapshots just do). Checked with outfit pictures and photos.
+
+Higher frame rates (in progress): the client steps its scene 30 times a second (SceneWindow.dll's `runApp`), and
+draws a window's frame on WM_PAINT. The adapter's frame pacer (`adapter/frame_pacer.cpp`) asks the 3D windows to
+repaint between steps at the user's rate (T5DE's settings, Graphics: `HKCU\Software\T5DE\Graphics\FrameRate`), only
+leaving the client idle time, and never holding up the next step: the adapter records the client's steps by replacing
+`SceneViewer::step`'s entry in its exported vtable (`adapter/scene_hooks.cpp`, after checking it), and a frame that
+wouldn't end before the step is due isn't asked for (a late step makes the client catch up two at once: hitches).
+While the renderer process covers the view, the client's renderer doesn't begin or present frames (its present can
+wait for the display). The renderer process takes each view's chunks on a thread of its own as they come, so the
+client never waits for drawing; it draws the newest frame. On a PC with a graphics card a room frame takes the client
+about 2.5 ms (the client's own work: posing avatars, which it does every frame, and walking the scene), and the
+renderer process about 0.5 ms.
+
+Between steps, the frames show the scene at the time between them (`adapter/scene_hooks.cpp`): avatars posed with
+their animations a fraction of a frame on (ModelInstance::render's call to updateCalSkeleton, redirected; Cal3D poses
+between keyframes; animations held, looping or starting are posed as they are), and the camera where its easing (a
+share 0.4 of the way to its target per step) has brought it, `1 - 0.6^fraction` of the way (CameraController's
+getCameraTransform, in its exported vtable). Nothing is predicted: both are what the next step would give, at the
+fraction; and particles moved on by their velocity times the time since the step (ModelInstance::render's call to
+ParticleSystem::render, redirected), then back by the same (the client sorts them by distance as it draws them, which
+reorders them); and crossfades between animations (weights ramped in tenths over 10 steps by ModelInstance::step),
+partway to the next step's weights. Still at 30 per second: gaze (heads turning to whoever's talking).
+
+Next: sharing pipelines between views (each view's scene compiles its own).
+
+## Building
+
+Two presets, one per architecture: `cmake --workflow --preset adapter` (32-bit, with the tests) and
+`cmake --workflow --preset renderer` (64-bit; the first configure fetches and builds Diligent). Both programs go in
+the client's folder.

docs/interface.md

@@ -59,9 +59,39 @@ virtual methods, IMVU's code only uses an engine through helpers that call its v
   `destroy`, `get_deleter`, `get_untyped_deleter`), the use count and the weak count, changed atomically.
   `include/t5de/imvu/shared_ptr.hpp` matches it. With non-trivial copy and destruction, it's returned through a
   hidden pointer and passed on the stack, as IMVU's code expects.
-- Still to work out, for a renderer of our own: `Mat4f`, `Transform`, `LightProperties`, `TextureTransform`,
-  `Pixmap` (`pixmap.dll`), the buffers' contents, `VertexAttributeArray<T>`, `std::vector<PointSprite>` as
-  Visual C++ 2010 lays it out, and `RenderBlendMode`'s values.
+- The data types are in `include/t5de/imvu/types.hpp`, worked out from the Direct3D engine: matrices and
+  transforms in Direct3D's row-vector convention, colors as `0xAARRGGBB`, lights (point or directional), blend
+  modes, linear fog, texture coordinate transforms, vertex attribute arrays (data, count, stride). `Pixmap` is used
+  through `pixmap.dll`'s exported methods (`width`, `height`, `pitch`, `pixels`, ...), not its layout.
+- `drawTriangles`' vertex buffers are positions (`Vec3f`), normals (`Vec3f`), texture coordinates (`Vec2f`) and
+  colors; vertex buffers are made with a stride, element size and count, dynamic ones filled later through the
+  buffer's own `update`. The objects an engine creates (buffers, textures, render targets) are declared in
+  `include/t5de/imvu/resources.hpp`; IMVU's code deletes them through their virtual destructors.
+- Checked in the client with the pass-through's logged arguments: a right-handed perspective projection (45 degree
+  vertical field of view, Direct3D's 0 to 1 depth) and an orthographic one for 2D, orthonormal view rotations,
+  opaque clear colors, ambient light with zero alpha, linear fog (1 to 50), scrolling texture transforms. Furniture
+  vertices are interleaved: positions and normals are 12-byte elements 32 bytes apart, so strides matter.
+- Projections give depth from -1 to 1, as OpenGL's do: IMVU's Direct3D renderer multiplies them by a matrix
+  mapping it to 0 to 1 (z' = z / 2 + w / 2) and shifting them half a pixel (-1 / width, +1 / height, for Direct3D
+  9's pixel centers). Without the depth mapping, everything in the nearer half of the depth range is clipped: the
+  2D overlay (name tags, the frame rate, the room's title) is drawn at depth -0.98.
+- The 2D overlay is ordinary `drawTriangles` with an orthographic projection (a few per frame), textured with text
+  IMVU draws with GDI into bitmaps.
+- Particles (`drawPointSprites`): a Visual C++ 2010 `std::vector` of 16-byte points (position, color), drawn as
+  Direct3D 9 point sprites: squares viewport height / distance pixels across (IMVU sets the size, 1, and the scale
+  factors 0, 0, 1), textured over the whole square. Direct3D 9's documented 64-pixel default limit doesn't apply in
+  practice: clamped to it they look much smaller and fainter than the client's.
+- Fog: linear table fog, start 1 and end 50 in rooms. Fogging by view depth matches the client; by depth buffer
+  value (as Direct3D 9's documentation suggests for projections like IMVU's) doesn't.
+- Render targets (`include/t5de/imvu/resources.hpp`): the engine returns each as a pointer into its own object;
+  the client calls only their interfaces' methods and passes them to `beginRendering`. A pixmap render target has one
+  method, `getPixmap()` (a Pixmap returned by value), with the pixels of the last frame drawn into it (IMVU's engine
+  copies them from the GPU at the frame's end). A texture render target has `area()` (always 0, 0, 1, 1) and
+  `texture()` (a new texture object for what's been drawn, as a shared pointer returned by value). The client uses
+  pixmap targets for snapshots (`takeSnapshot`: outfit pictures, the photo widget), 2048x2048; texture targets
+  haven't been seen used. Pixmap is 28 bytes; pixmap.dll exports its constructors and destructor.
+- Still unknown: `CompoundRegion` (texture update regions), `newRenderTexture`'s flags, and what `beginRendering` does with a null target. MSVC orders overloaded
+  virtual methods unlike their declaration, so our declarations never overload virtual methods.
 - Memory crosses the boundary only through virtual methods (destructors, control blocks), so each side can use its
   own C runtime. Exceptions must not cross it.
 

include/t5de/imvu/render_engine.hpp

@@ -1,54 +1,16 @@
 #pragma once
 // IMVU's renderer interface, PiRenderEngine (SceneWindow.dll), declared to match its vtable: the order of the methods
 // and their parameter types are what matter. The names are IMVU's, from SceneWindow.dll's exported RenderEngineDx
-// methods; parameter names are ours, and guesses until the calls are traced. Types used only through pointers or
-// references are left incomplete until we need their layout. See docs/interface.md.
+// methods; parameter names are ours, from what IMVU's Direct3D engine does with them. See docs/interface.md.
 
 #include <cstdint>
 
+#include "t5de/imvu/resources.hpp"
 #include "t5de/imvu/shared_ptr.hpp"
+#include "t5de/imvu/types.hpp"
 
 namespace t5de::imvu {
 
-template <class T>
-struct Vec2 {
-    T x;
-    T y;
-};
-
-template <class T>
-struct Vec3 {
-    T x;
-    T y;
-    T z;
-};
-
-using Vec2i = Vec2<int>;
-using Vec2f = Vec2<float>;
-using Vec3f = Vec3<float>;
-
-struct Mat4f;
-struct Transform;
-struct LightProperties;
-struct TextureTransform;
-struct PointSprite;
-class Pixmap;
-class INativeWindow;
-class PiRenderTexture;
-class PiInternalIndexBuffer;
-class PiInternalVertexBuffer;
-class PiRenderTarget;
-class PiPixmapRenderTarget;
-class PiTextureRenderTarget;
-template <class T>
-class VertexAttributeArray;
-
-// std::vector<PointSprite> as Visual C++ 2010 lays it out.
-struct PointSpriteVector;
-
-// Values not yet known.
-enum class RenderBlendMode : int {};
-
 class PiRenderEngine {
 public:
     PiRenderEngine() = default;
@@ -59,7 +21,7 @@ public:
 
     virtual void resizeFrameBuffer(Vec2i size) = 0;
     virtual void enable2dFrameBuffer() = 0;
-    virtual void clear(std::uint32_t flags, std::uint32_t color) = 0;
+    virtual void clear(std::uint32_t flags, Color color) = 0; // ClearFlags
     virtual void setProjection(Vec2i viewport, const Mat4f& projection) = 0;
     virtual void setModelSpace(const Transform& model) = 0; // slot 5
     virtual void setViewSpace(const Transform& view) = 0;
@@ -75,29 +37,33 @@ public:
     virtual void setLightingOn(bool on) = 0;
     virtual void setLightProperties(std::uint32_t index, const LightProperties& light) = 0;
     virtual void setFogOn(bool on) = 0;
-    virtual void setFogAttributes(float start, float end, std::uint32_t color) = 0;
+    virtual void setFogAttributes(float start, float end, Color color) = 0;
     virtual void setTextureTransformMatrixIdentity(std::uint32_t stage) = 0; // slot 20
     virtual void setTextureTransformMatrix(std::uint32_t stage, const TextureTransform& transform) = 0;
-    virtual void setEnvironmentAmbient(std::uint32_t color) = 0;
-    virtual PiRenderTexture* newRenderTexture(Pixmap* pixmap, std::uint32_t flags) = 0;
+    virtual void setEnvironmentAmbient(Color color) = 0; // zero alpha
+    virtual PiRenderTexture* newRenderTexture(const Pixmap& pixmap, std::uint32_t flags) = 0;
     virtual PiInternalIndexBuffer* newIndexBuffer(std::uint32_t count, const std::uint16_t* indices) = 0;
-    virtual PiInternalVertexBuffer* newStaticVertexBuffer(const void* data, std::uint32_t a, std::uint32_t b,
-                                                          std::uint32_t c) = 0; // slot 25
-    virtual PiInternalVertexBuffer* newDynamicVertexBuffer(std::uint32_t a, std::uint32_t b) = 0;
+    virtual PiInternalVertexBuffer* newStaticVertexBuffer(const void* data, std::uint32_t stride,
+                                                          std::uint32_t elementSize,
+                                                          std::uint32_t elementCount) = 0; // slot 25
+    // Filled later with PiInternalVertexBuffer::update.
+    virtual PiInternalVertexBuffer* newDynamicVertexBuffer(std::uint32_t elementSize, std::uint32_t elementCount) = 0;
     virtual SharedPtr<PiPixmapRenderTarget> newPixmapRenderTarget(Vec2i size) = 0;
     virtual SharedPtr<PiTextureRenderTarget> newTextureRenderTarget(Vec2i size) = 0;
     virtual void beginRendering(PiRenderTarget* target) = 0;
     virtual void endRendering() = 0; // slot 30
+    // Vertex buffers: positions (Vec3f), normals (Vec3f), texture coordinates (Vec2f), colors (Color); all but
+    // positions may be null.
     virtual void drawTriangles(PiInternalIndexBuffer* indices, PiInternalVertexBuffer* positions,
-                               PiInternalVertexBuffer* normals, PiInternalVertexBuffer* texCoords0,
-                               PiInternalVertexBuffer* texCoords1) = 0;
+                               PiInternalVertexBuffer* normals, PiInternalVertexBuffer* texCoords,
+                               PiInternalVertexBuffer* colors) = 0;
     virtual void drawLine(Vec3f from, Vec3f to, std::uint32_t color) = 0;
     virtual void drawPointSprites(const PointSpriteVector& sprites) = 0;
     virtual void drawTrianglesFromMemory(std::uint32_t vertexCount, std::uint32_t indexCount,
                                          const std::uint16_t* indices, const VertexAttributeArray<Vec3f>& positions,
                                          const VertexAttributeArray<Vec3f>& normals,
                                          const VertexAttributeArray<Vec2f>& texCoords,
-                                         const VertexAttributeArray<std::uint32_t>& colors) = 0; // slot 34
+                                         const VertexAttributeArray<Color>& colors) = 0; // slot 34
 
 private:
     // PiRenderEngine's own fields, after the vtable pointer: a magic number IMVU's destructor checks, and a size

include/t5de/imvu/resources.hpp

@@ -0,0 +1,75 @@
+#pragma once
+// The objects a PiRenderEngine creates and hands to IMVU's code: buffers, textures, render targets. IMVU's code keeps
+// them, calls their virtual methods, and deletes them through their virtual destructors. Declared from the vtables in
+// SceneWindow.dll; method names are ours, from what IMVU's implementations do. Not yet verified by a renderer of our
+// own.
+
+#include <cstdint>
+
+#include "t5de/imvu/shared_ptr.hpp"
+#include "t5de/imvu/types.hpp"
+
+namespace t5de::imvu {
+
+class PiInternalIndexBuffer {
+public:
+    virtual ~PiInternalIndexBuffer() = default;
+};
+
+class PiInternalVertexBuffer {
+public:
+    virtual ~PiInternalVertexBuffer() = default;
+    // Replaces a dynamic buffer's contents: elementCount elements of elementSize bytes, stride bytes apart (a multiple
+    // of 4, at least elementSize). Element size and count are the ones the buffer was created with.
+    virtual void update(const void* data, std::uint32_t stride, std::uint32_t elementSize,
+                        std::uint32_t elementCount) = 0;
+    // Unknown: IMVU's software buffer forgets its data; its Direct3D buffer asserts, so it isn't called there.
+    virtual void unknown2() = 0;
+};
+
+class PiRenderTexture {
+public:
+    virtual ~PiRenderTexture() = default;
+    virtual Vec2i size() const = 0;
+    // Copies the parts of pixmap in regions into the texture. (Not overloaded with update: MSVC orders overloaded
+    // virtual methods unlike their declaration.)
+    virtual void updateRegions(const Pixmap& pixmap, const CompoundRegion& regions) = 0;
+    // Copies all of pixmap into the texture.
+    virtual void update(const Pixmap& pixmap) = 0;
+    // Reads the texture into a new Pixmap, constructed in result (a Pixmap returned by value).
+    virtual Pixmap* read(Pixmap* result) const = 0;
+};
+
+// What frames can be drawn into besides the window (PiRenderEngine::beginRendering). IMVU's Direct3D engine returns
+// each as a pointer into its own object (single inheritance from these, so the PiRenderTarget pointer is the same).
+class PiRenderTarget {
+public:
+    virtual ~PiRenderTarget() = default;
+};
+
+// Drawn into, then read: after each frame drawn into it, getPixmap() has its pixels (IMVU's engine copies them at the
+// end of the frame). Used for snapshots: outfit pictures, the photo widget.
+class PiPixmapRenderTarget : public PiRenderTarget {
+public:
+    // Constructs a copy of the pixels in result (a Pixmap returned by value).
+    virtual Pixmap* getPixmap(Pixmap* result) const = 0;
+};
+
+// The part of the texture the target covers, in texture coordinates. IMVU's Direct3D engine always returns 0, 0, 1, 1.
+struct TextureArea {
+    float left;
+    float top;
+    float right;
+    float bottom;
+};
+
+// Drawn into, then drawn with as a texture.
+class PiTextureRenderTarget : public PiRenderTarget {
+public:
+    // Constructs the area in result (returned by value).
+    virtual TextureArea* area(TextureArea* result) const = 0;
+    // Constructs, in result, a new texture object for what's been drawn (a shared pointer returned by value).
+    virtual SharedPtr<PiRenderTexture>* texture(SharedPtr<PiRenderTexture>* result) const = 0;
+};
+
+} // namespace t5de::imvu

include/t5de/imvu/types.hpp

@@ -0,0 +1,126 @@
+#pragma once
+// The data types IMVU's renderer interface passes, as SceneWindow.dll's Direct3D 9 engine reads them. Most are passed
+// by reference: where IMVU's type might hold more than we read, its size isn't asserted. See docs/interface.md.
+
+#include <cstddef>
+#include <cstdint>
+
+struct HWND__; // windows.h's window handle type (HWND is HWND__*)
+
+namespace t5de::imvu {
+
+template <class T>
+struct Vec2 {
+    T x;
+    T y;
+};
+
+template <class T>
+struct Vec3 {
+    T x;
+    T y;
+    T z;
+};
+
+using Vec2i = Vec2<int>;
+using Vec2f = Vec2<float>;
+using Vec3f = Vec3<float>;
+
+// Colors are 0xAARRGGBB (Direct3D's D3DCOLOR). Light and ambient colors must have zero alpha.
+using Color = std::uint32_t;
+
+// A 4x4 matrix in Direct3D's convention: row-major, transforming row vectors (p' = p * M).
+struct Mat4f {
+    float m[4][4];
+};
+
+// An affine transform: a 3x3 matrix (row-major), then a translation; p' = p * linear + translation, as in Direct3D.
+// The Direct3D engine expands it to [linear 0; translation 1]. (What it reads; IMVU's type may be larger.)
+struct Transform {
+    float linear[3][3];
+    Vec3f translation;
+};
+
+// A texture coordinate transform: u' = u * m[0] + v * m[1] + m[4], v' = u * m[2] + v * m[3] + m[5].
+struct TextureTransform {
+    float m[6];
+};
+
+enum class LightType : int {
+    Point = 0,       // at `vector`; the Direct3D engine sets no attenuation and a fixed range
+    Directional = 1, // shining along -`vector` (a zero vector means along -x)
+};
+
+// What the Direct3D engine reads of a light. (IMVU's type may be larger.)
+struct LightProperties {
+    bool enabled;
+    Color diffuse; // zero alpha
+    Vec3f vector;
+    LightType type;
+};
+
+static_assert(offsetof(LightProperties, diffuse) == 4 && offsetof(LightProperties, vector) == 8
+              && offsetof(LightProperties, type) == 0x14);
+
+// Blend functions, as source and destination factors.
+enum class RenderBlendMode : int {
+    Alpha = 1,         // source alpha, inverse source alpha
+    Additive = 2,      // one, one
+    Premultiplied = 3, // one, inverse source alpha
+    AdditiveAlpha = 4, // source alpha, one
+};
+
+// clear()'s flags.
+enum ClearFlags : std::uint32_t {
+    ClearColor = 1,
+    ClearDepth = 2, // to 1.0
+};
+
+// Vertex attributes in memory: count elements, stride bytes apart (0: packed).
+template <class T>
+struct VertexAttributeArray {
+    const T* data;
+    std::uint32_t count;
+    std::uint32_t stride;
+};
+
+static_assert(sizeof(VertexAttributeArray<Vec3f>) == 12);
+
+// IMVU's image class (pixmap.dll): 32-bit pixels (Color). Its layout isn't needed: pixmap.dll exports its methods
+// (width, height, pitch, rowBytes, pixels, ...).
+class Pixmap;
+
+// A particle (drawPointSprites): a point drawn as a camera-facing square, textured, about viewport height / distance
+// pixels across (1 to 64), as the Direct3D engine's point sprites are.
+struct PointSprite {
+    Vec3f position;
+    Color color;
+};
+
+static_assert(sizeof(PointSprite) == 16);
+
+// std::vector<PointSprite> as Visual C++ 2010 lays it out (release builds): its elements are [first, last).
+struct PointSpriteVector {
+    const PointSprite* first;
+    const PointSprite* last;
+    const PointSprite* end; // of the allocation
+};
+
+// Region lists IMVU passes to texture updates; unknown so far.
+class CompoundRegion;
+
+struct UiEvent;
+using NativeWindowHandle = ::HWND__*; // an HWND
+
+// IMVU's window (SceneWindow.dll's NativeWindow), as far as a renderer needs it: the first methods of its vtable.
+// Its later methods include overloads, which MSVC lays out unlike their declaration: declare them from the vtable
+// if they're ever needed.
+class INativeWindow {
+public:
+    virtual ~INativeWindow() = default;
+    virtual void handleMessage(UiEvent* event) = 0;
+    virtual int onSetCursor(Vec2i position) = 0;
+    virtual NativeWindowHandle getPlatformWindow() = 0;
+};
+
+} // namespace t5de::imvu

include/t5de/protocol/channel.hpp

@@ -0,0 +1,66 @@
+#pragma once
+// What the adapter (t5deRenderEngine.dll, in IMVU's 32-bit process) and the renderer process (64-bit) share. Both
+// are built from this header, for different architectures: fixed-size fields only, no pointers or handles' native
+// sizes.
+
+#include <cstdint>
+
+namespace t5de::protocol {
+
+inline constexpr std::uint32_t version = 5;
+
+// One renderer process draws all of a client's 3D views. A shared memory section the adapter creates once per client
+// process, named by the renderer process's `--control <name>` argument, holds this; each engine's channel is named
+// "<name>-<n>", n counting from 0. Having created a channel, the adapter increments channels and sets the event
+// "<name>-attach" (auto-reset); the renderer process opens the channels it hasn't yet (those already gone are
+// skipped), and stops drawing a channel's view when its engine sets closing. It exits with the client.
+struct Control {
+    std::uint32_t version;
+    std::uint32_t channels; // channels created so far
+};
+
+inline constexpr wchar_t attachEventSuffix[] = L"-attach";
+
+// Which part of the client's 3D view the renderer process draws. Full is the default; the others are for comparing
+// with the client's renderer, which then draws the whole view under the renderer process's window.
+enum class View : std::uint32_t {
+    Off,     // none
+    Split,   // the right half, to compare with the client's renderer on the left
+    Full,
+    Compare, // over the right half, the left half's scene: both renderers side by side, showing the same
+};
+
+// A shared memory section the adapter creates for each engine (named as Control says): this header, then `capacity`
+// bytes of data. The adapter sends the command stream (commands.hpp) through
+// it in chunks: it waits for the event "<name>-consumed", writes a chunk and sets "<name>-ready"; the renderer
+// process copies the chunk out and sets "<name>-consumed" (both auto-reset; consumed starts set).
+//
+// A frame drawn into a render target can ask for its pixels back (BeginFrame::readBack): having sent it, the adapter
+// waits for "<name>-read" (auto-reset), which the renderer process sets once it has drawn the frame and written the
+// pixels into the data area (readSize bytes: rows packed, 0xAARRGGBB; 0 if it couldn't). The adapter sends nothing
+// meanwhile, so the data area is free.
+struct Channel {
+    std::uint32_t version;
+    std::uint32_t closing; // nonzero: the engine is gone, the renderer process should exit
+    std::uint64_t window;  // IMVU's 3D window (an HWND; window handles are valid in every process)
+    std::uint64_t frames;  // frames the client has drawn
+    View view;
+    std::uint32_t capacity;
+    std::uint32_t chunkSize;
+    std::uint32_t chunkFlags; // chunkEndsFrame
+    // Set by the renderer process while its window covers the whole 3D view and it's presenting frames: the client's
+    // renderer then needn't draw (the adapter skips its draws; it draws again as soon as this is cleared).
+    std::uint32_t covering;
+    std::uint32_t readSize;
+};
+
+static_assert(sizeof(Channel) == 48, "same layout in 32-bit and 64-bit builds");
+
+inline constexpr std::uint32_t chunkEndsFrame = 1;
+inline constexpr std::uint32_t channelCapacity = 16 * 1024 * 1024;
+
+inline constexpr wchar_t readyEventSuffix[] = L"-ready";
+inline constexpr wchar_t consumedEventSuffix[] = L"-consumed";
+inline constexpr wchar_t readEventSuffix[] = L"-read";
+
+} // namespace t5de::protocol

include/t5de/protocol/commands.hpp

@@ -0,0 +1,280 @@
+#pragma once
+// The command stream: what the adapter records from IMVU's renderer interface, and the renderer process carries out.
+// Each command is a Header, its fixed-size body, then for some a variable-size payload (pixels, vertex data),
+// padded to 4 bytes. Built for 32-bit and 64-bit: fixed-size fields only.
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <optional>
+#include <span>
+#include <vector>
+
+namespace t5de::protocol {
+
+enum class Op : std::uint16_t {
+    BeginFrame = 1,
+    EndFrame,
+    Clear,
+    SetProjection,
+    SetModel,
+    SetView,
+    SetTextures,
+    SetState,
+    SetLight,
+    SetFog,
+    SetTextureTransform,
+    CreateTexture,
+    UpdateTexture,
+    DestroyTexture,
+    CreateBuffer,
+    UpdateBuffer,
+    DestroyBuffer,
+    DrawTriangles,
+    DrawArrays,
+    DrawPointSprites,
+    CreateRenderTarget,
+};
+
+struct Header {
+    Op op;
+    std::uint16_t reserved;
+    std::uint32_t size; // of the body and payload, padded to 4 bytes
+};
+
+// Colors are 0xAARRGGBB. Resource ids are the adapter's, per engine; 0 means none.
+
+struct BeginFrame {
+    // The render target drawn into (CreateRenderTarget's id), 0 for the window, or foreignTarget.
+    std::uint32_t target;
+    std::uint32_t readBack; // at the end of the frame, send the render target's pixels back (channel.hpp)
+};
+
+// A frame drawn into a render target of the client renderer's own (made while the renderer process wasn't running):
+// the client renderer draws it, the renderer process only follows its changes.
+inline constexpr std::uint32_t foreignTarget = 0xffffffff;
+
+struct EndFrame {
+    std::uint64_t sentAt; // the adapter's QueryPerformanceCounter (the same clock in every process)
+};
+
+struct Clear {
+    std::uint32_t flags; // 1: color, 2: depth (to 1)
+    std::uint32_t color;
+};
+
+// The viewport's size, and a Direct3D projection matrix (row-major, row vectors).
+struct SetProjection {
+    std::int32_t width;
+    std::int32_t height;
+    float m[16];
+};
+
+// An affine transform (SetModel, SetView): a 3x3 matrix, row-major, then the translation.
+struct SetTransform {
+    float m[12];
+};
+
+struct SetTextures {
+    std::uint32_t texture0;
+    std::uint32_t texture1;
+};
+
+enum class State : std::uint32_t {
+    DepthTest,
+    DepthWrite,
+    Blending,
+    BlendMode,      // 1: alpha, 2: additive, 3: premultiplied, 4: additive alpha
+    AlphaTest,
+    AlphaReference, // 0-255: pixels pass if their alpha is greater
+    Culling,
+    NormalInverting, // flips which winding faces front
+    Lighting,
+    Fog,
+    Ambient,         // a color
+};
+
+struct SetState {
+    State state;
+    std::uint32_t value;
+};
+
+struct SetLight {
+    std::uint32_t index;
+    std::uint32_t enabled;
+    std::uint32_t color;
+    std::uint32_t directional; // 0: a point light at vector; 1: light coming from direction vector
+    float vector[3];
+};
+
+struct SetFog {
+    float start;
+    float end;
+    std::uint32_t color;
+};
+
+// Texture coordinates for a stage: u' = u * m[0] + v * m[1] + m[4], v' = u * m[2] + v * m[3] + m[5].
+struct SetTextureTransform {
+    std::uint32_t stage;
+    std::uint32_t identity;
+    float m[6];
+};
+
+// Payload: width * height pixels (0xAARRGGBB), rows packed.
+struct CreateTexture {
+    std::uint32_t id;
+    std::uint32_t width;
+    std::uint32_t height;
+    std::uint32_t flags; // 2: wrap u, 4: wrap v (else clamp)
+};
+
+struct UpdateTexture {
+    std::uint32_t id;
+    std::uint32_t width;
+    std::uint32_t height;
+};
+
+struct DestroyTexture {
+    std::uint32_t id;
+};
+
+// A texture frames can be drawn into (BeginFrame), and drawn with like any other; destroyed with DestroyTexture.
+struct CreateRenderTarget {
+    std::uint32_t id;
+    std::uint32_t width;
+    std::uint32_t height;
+};
+
+enum class BufferKind : std::uint32_t {
+    Index,  // 16-bit indices
+    Vertex, // positions and normals (3 floats), texture coordinates (2 floats) or colors (0xAARRGGBB)
+};
+
+// Payload: count elements of elementSize bytes, packed; empty for a buffer filled later (UpdateBuffer).
+struct CreateBuffer {
+    std::uint32_t id;
+    BufferKind kind;
+    std::uint32_t elementSize;
+    std::uint32_t count;
+};
+
+struct UpdateBuffer {
+    std::uint32_t id;
+    std::uint32_t elementSize;
+    std::uint32_t count;
+};
+
+struct DestroyBuffer {
+    std::uint32_t id;
+};
+
+// Triangles from buffers: indices and positions are required, the others optional.
+struct DrawTriangles {
+    std::uint32_t indices;
+    std::uint32_t positions;
+    std::uint32_t normals;
+    std::uint32_t texCoords;
+    std::uint32_t colors;
+};
+
+// Triangles from data in the payload, packed: indexCount 16-bit indices (padded to 4 bytes), then vertexCount
+// positions, and normals, texture coordinates and colors if present.
+struct DrawArrays {
+    std::uint32_t vertexCount;
+    std::uint32_t indexCount;
+    std::uint32_t hasNormals;
+    std::uint32_t hasTexCoords;
+    std::uint32_t hasColors;
+};
+
+// Particles: payload count sprites of 16 bytes, a position (3 floats) and a color. Each is a camera-facing square,
+// viewport height / distance pixels across (1 to 64), textured with the first texture over the whole square.
+struct DrawPointSprites {
+    std::uint32_t count;
+};
+
+static_assert(sizeof(Header) == 8 && sizeof(SetProjection) == 72 && sizeof(SetLight) == 28
+              && sizeof(DrawArrays) == 20);
+
+inline constexpr std::size_t padded(std::size_t size) { return (size + 3) & ~std::size_t{3}; }
+
+// Appends commands to a byte buffer.
+class Writer {
+public:
+    // Appends a command and returns its payload, payloadSize bytes for the caller to fill.
+    template <class Body>
+    std::byte* add(Op op, const Body& body, std::size_t payloadSize = 0)
+    {
+        static_assert(sizeof(Body) % 4 == 0);
+        const std::size_t size = sizeof(Body) + padded(payloadSize);
+        const std::size_t start = bytes_.size();
+        bytes_.resize(start + sizeof(Header) + size);
+        const Header header{op, 0, static_cast<std::uint32_t>(size)};
+        std::memcpy(bytes_.data() + start, &header, sizeof(Header));
+        std::memcpy(bytes_.data() + start + sizeof(Header), &body, sizeof(Body));
+        return bytes_.data() + start + sizeof(Header) + sizeof(Body);
+    }
+
+    [[nodiscard]] std::span<const std::byte> bytes() const { return bytes_; }
+    [[nodiscard]] std::size_t size() const { return bytes_.size(); }
+    void clear() { bytes_.clear(); }
+
+private:
+    std::vector<std::byte> bytes_;
+};
+
+// One command, as read back.
+class Command {
+public:
+    Command(Op op, std::span<const std::byte> data) : op_(op), data_(data) {}
+
+    [[nodiscard]] Op op() const { return op_; }
+
+    // The body, if the command is long enough to hold one.
+    template <class Body>
+    [[nodiscard]] std::optional<Body> body() const
+    {
+        if (data_.size() < sizeof(Body)) {
+            return std::nullopt;
+        }
+        Body body;
+        std::memcpy(&body, data_.data(), sizeof(Body));
+        return body;
+    }
+
+    template <class Body>
+    [[nodiscard]] std::span<const std::byte> payload() const
+    {
+        return data_.size() < sizeof(Body) ? std::span<const std::byte>{} : data_.subspan(sizeof(Body));
+    }
+
+private:
+    Op op_;
+    std::span<const std::byte> data_;
+};
+
+// Reads commands back from a byte buffer; stops at the end, or at a truncated command.
+class Reader {
+public:
+    explicit Reader(std::span<const std::byte> bytes) : bytes_(bytes) {}
+
+    std::optional<Command> next()
+    {
+        if (bytes_.size() < sizeof(Header)) {
+            return std::nullopt;
+        }
+        Header header;
+        std::memcpy(&header, bytes_.data(), sizeof(Header));
+        if (bytes_.size() - sizeof(Header) < header.size) {
+            return std::nullopt;
+        }
+        Command command(header.op, bytes_.subspan(sizeof(Header), header.size));
+        bytes_ = bytes_.subspan(sizeof(Header) + header.size);
+        return command;
+    }
+
+private:
+    std::span<const std::byte> bytes_;
+};
+
+} // namespace t5de::protocol

renderer/CMakeLists.txt

@@ -0,0 +1,40 @@
+# t5de-renderer.exe, the 64-bit renderer process, drawing with Diligent Engine.
+
+include(FetchContent)
+
+# Diligent Engine's core, pinned to an exact commit. Only the Direct3D 11 backend for now; the others (Direct3D 12,
+# Vulkan for ray tracing and mesh shaders, WebGPU for browsers) are switched on as they're needed.
+set(DILIGENT_NO_DIRECT3D12 ON CACHE BOOL "" FORCE)
+set(DILIGENT_NO_VULKAN ON CACHE BOOL "" FORCE)
+set(DILIGENT_NO_OPENGL ON CACHE BOOL "" FORCE)
+set(DILIGENT_NO_WEBGPU ON CACHE BOOL "" FORCE)
+set(DILIGENT_NO_ARCHIVER ON CACHE BOOL "" FORCE)
+set(DILIGENT_NO_SUPER_RESOLUTION ON CACHE BOOL "" FORCE)
+set(DILIGENT_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+set(DILIGENT_INSTALL_CORE OFF CACHE BOOL "" FORCE)
+FetchContent_Declare(DiligentCore
+    GIT_REPOSITORY https://github.com/DiligentGraphics/DiligentCore.git
+    GIT_TAG c555e4d26de3f414eaf792fa16c0c24827619b17 # master, 2026-10-27
+    GIT_SUBMODULES ThirdParty/xxHash
+    EXCLUDE_FROM_ALL
+    SYSTEM)
+FetchContent_MakeAvailable(DiligentCore)
+
+# Shader sources, embedded in the program (Diligent compiles them at run time): each shaders/<name>.hlsl becomes
+# <name>_hlsl.hpp, defining <camelCaseName>Hlsl.
+function(t5de_embed_shader file name)
+    set(T5DE_SHADER_FILE ${file})
+    set(T5DE_SHADER_NAME ${name})
+    file(READ ${CMAKE_CURRENT_SOURCE_DIR}/shaders/${file} T5DE_SHADER_SOURCE)
+    get_filename_component(stem ${file} NAME_WE)
+    configure_file(shaders/embed.hpp.in ${CMAKE_CURRENT_BINARY_DIR}/generated/${stem}_hlsl.hpp @ONLY)
+    set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS shaders/${file})
+endfunction()
+t5de_embed_shader(fixed_function.hlsl fixedFunctionHlsl)
+
+add_executable(t5de_renderer WIN32 log.cpp main.cpp scene.cpp)
+set_target_properties(t5de_renderer PROPERTIES OUTPUT_NAME t5de-renderer)
+target_include_directories(t5de_renderer PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/generated)
+target_link_libraries(t5de_renderer PRIVATE t5de::protocol t5de::options Diligent-GraphicsEngineD3D11-static Diligent-Common)
+
+install(TARGETS t5de_renderer RUNTIME DESTINATION .)

renderer/log.cpp

@@ -0,0 +1,30 @@
+#include "log.hpp"
+
+#include <windows.h>
+
+#include <filesystem>
+#include <string>
+
+namespace t5de::log {
+
+// Each line is one appending write, so lines from several processes don't mix.
+void write(std::string_view line)
+{
+    static const HANDLE file = [] {
+        wchar_t temp[MAX_PATH + 1];
+        const DWORD length = GetTempPathW(MAX_PATH + 1, temp);
+        if (length == 0 || length > MAX_PATH) {
+            return INVALID_HANDLE_VALUE;
+        }
+        return CreateFileW((std::filesystem::path(temp) / L"t5de-renderer-process.log").c_str(), FILE_APPEND_DATA,
+                           FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr, OPEN_ALWAYS,
+                           FILE_ATTRIBUTE_NORMAL, nullptr);
+    }();
+    if (file != INVALID_HANDLE_VALUE) {
+        const std::string text = std::format("{}: {}\n", GetCurrentProcessId(), line);
+        DWORD written = 0;
+        WriteFile(file, text.data(), static_cast<DWORD>(text.size()), &written, nullptr);
+    }
+}
+
+} // namespace t5de::log

renderer/log.hpp

@@ -0,0 +1,18 @@
+#pragma once
+// The renderer processes' log: %TEMP%\t5de-renderer-process.log, shared by all of them (lines start with the pid).
+
+#include <format>
+#include <string_view>
+#include <utility>
+
+namespace t5de::log {
+
+void write(std::string_view line);
+
+template <class... Args>
+void info(std::format_string<Args...> format, Args&&... args)
+{
+    write(std::format(format, std::forward<Args>(args)...));
+}
+
+} // namespace t5de::log

renderer/main.cpp

@@ -0,0 +1,486 @@
+// t5de-renderer.exe: the renderer process. Started by the adapter (t5deRenderEngine.dll), one for the whole client:
+// receives each 3D view's drawing as commands through a shared memory channel of its own, and draws it with Diligent
+// into a child window it places over the view in the client's window.
+
+#include <windows.h>
+
+#include <d3d11.h>
+#include <dxgi.h>
+#include <shellapi.h>
+
+#include <algorithm>
+#include <atomic>
+#include <cstdint>
+#include <cstring>
+#include <filesystem>
+#include <format>
+#include <memory>
+#include <mutex>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <thread>
+#include <vector>
+
+#include "EngineFactoryD3D11.h"
+#include "RefCntAutoPtr.hpp"
+#include "RenderDeviceD3D11.h"
+#include "log.hpp"
+#include "scene.hpp"
+#include "t5de/protocol/channel.hpp"
+
+namespace {
+
+using namespace Diligent;
+using t5de::protocol::Channel;
+using t5de::protocol::View;
+
+using t5de::log::info;
+
+// Diligent's messages (shader compilation errors, invalid states, ...), into the log.
+void DILIGENT_CALL_TYPE diligent_message(DEBUG_MESSAGE_SEVERITY severity, const Char* message, const Char* function,
+                                         const Char*, int)
+{
+    static constexpr const char* severities[] = {"info", "warning", "error", "fatal error"};
+    info("Diligent {}: {}{}{}", severities[severity < 4 ? severity : 3], function != nullptr ? function : "",
+         function != nullptr ? ": " : "", message != nullptr ? message : "");
+}
+
+struct Arguments {
+    std::wstring control;
+    DWORD parent = 0;
+};
+
+Arguments parse_arguments()
+{
+    Arguments arguments;
+    int count = 0;
+    wchar_t** argv = CommandLineToArgvW(GetCommandLineW(), &count);
+    for (int i = 1; i + 1 < count; i += 2) {
+        const std::wstring_view name = argv[i];
+        if (name == L"--control") {
+            arguments.control = argv[i + 1];
+        } else if (name == L"--parent") {
+            arguments.parent = static_cast<DWORD>(std::wcstoul(argv[i + 1], nullptr, 10));
+        }
+    }
+    LocalFree(argv);
+    return arguments;
+}
+
+std::string narrow(const std::wstring& text) { return std::filesystem::path(text).string(); }
+
+LRESULT CALLBACK window_procedure(HWND window, UINT message, WPARAM wparam, LPARAM lparam)
+{
+    if (message == WM_ERASEBKGND) {
+        return 1; // we draw all of it
+    }
+    return DefWindowProcW(window, message, wparam, lparam);
+}
+
+// A child of the client's window. Disabled, so mouse input goes to the client's window under it.
+HWND create_child_window(HWND parent)
+{
+    static const ATOM windowClass = [] {
+        const WNDCLASSEXW description{.cbSize = sizeof(WNDCLASSEXW),
+                                      .lpfnWndProc = window_procedure,
+                                      .hInstance = GetModuleHandleW(nullptr),
+                                      .hCursor = LoadCursorW(nullptr, IDC_ARROW),
+                                      .lpszClassName = L"T5DERenderer"};
+        return RegisterClassExW(&description);
+    }();
+    return CreateWindowExW(0, MAKEINTATOM(windowClass), L"", WS_CHILD | WS_VISIBLE | WS_DISABLED | WS_CLIPSIBLINGS, 0,
+                           0, 1, 1, parent, nullptr, GetModuleHandleW(nullptr), nullptr);
+}
+
+// The view, as the adapter set it, or as %TEMP%\t5de-renderer-view.txt says while the client runs (off, split, full
+// or compare): for comparing the renderers without restarting the client. Read every second or so.
+View current_view(View adapter)
+{
+    static std::optional<View> view;
+    static ULONGLONG checked = 0;
+    if (GetTickCount64() - checked >= 1000) {
+        checked = GetTickCount64();
+        view.reset();
+        wchar_t temp[MAX_PATH + 1];
+        const DWORD length = GetTempPathW(MAX_PATH + 1, temp);
+        const HANDLE file = length == 0 || length > MAX_PATH
+                                ? INVALID_HANDLE_VALUE
+                                : CreateFileW((std::filesystem::path(temp) / L"t5de-renderer-view.txt").c_str(),
+                                              GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                                              nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+        if (file != INVALID_HANDLE_VALUE) {
+            char text[16] = {};
+            DWORD read = 0;
+            ReadFile(file, text, sizeof(text) - 1, &read, nullptr);
+            CloseHandle(file);
+            const std::string_view setting(text, std::strcspn(text, "\r\n "));
+            if (setting == "off") {
+                view = View::Off;
+            } else if (setting == "split") {
+                view = View::Split;
+            } else if (setting == "full") {
+                view = View::Full;
+            } else if (setting == "compare") {
+                view = View::Compare;
+            }
+        }
+    }
+    return view.value_or(adapter);
+}
+
+// Shader changes to try while the client runs: %TEMP%\t5de-renderer-shaders\fixed_function.hlsl, if there is
+// one, replaces the built-in shaders, and is read again when it changes (checked every second or so). Returns the
+// new source when it has changed.
+std::optional<std::string> changed_shaders()
+{
+    static ULONGLONG checked = 0;
+    static std::filesystem::file_time_type loaded{};
+    if (GetTickCount64() - checked < 1000) {
+        return std::nullopt;
+    }
+    checked = GetTickCount64();
+    std::error_code error;
+    const auto path = std::filesystem::temp_directory_path(error) / L"t5de-renderer-shaders" / L"fixed_function.hlsl";
+    const auto modified = std::filesystem::last_write_time(path, error);
+    if (error || modified == loaded) {
+        return std::nullopt;
+    }
+    const HANDLE file = CreateFileW(path.c_str(), GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, nullptr,
+                                    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+    if (file == INVALID_HANDLE_VALUE) {
+        return std::nullopt;
+    }
+    std::string source(static_cast<std::size_t>(std::filesystem::file_size(path, error)), ' ');
+    DWORD read = 0;
+    ReadFile(file, source.data(), static_cast<DWORD>(source.size()), &read, nullptr);
+    CloseHandle(file);
+    source.resize(read);
+    loaded = modified;
+    info("shaders reloaded from {}", path.string());
+    return source;
+}
+
+// Where the child window goes in the client's 3D view, and where in the 3D view its scene starts (offset).
+struct Placement {
+    RECT window{};
+    int offset = 0;
+};
+
+Placement placement(HWND parent, View view)
+{
+    Placement place;
+    GetClientRect(parent, &place.window);
+    if (view == View::Split || view == View::Compare) {
+        place.window.left = place.window.right / 2;
+    }
+    place.offset = view == View::Compare ? 0 : place.window.left;
+    if (view == View::Off) {
+        place.window = {};
+    }
+    return place;
+}
+
+// One of the client's 3D views: an engine's channel, and the child window its frames are drawn into. A thread of its
+// own takes the channel's chunks as soon as they come (so the client never waits for drawing) and queues them; the main
+// thread draws the newest complete frame, carrying out older ones' changes without drawing them.
+class ViewWindow {
+public:
+    // Opens the channel named name and sets up its window; null if the channel is gone or it can't.
+    static std::unique_ptr<ViewWindow> open(const std::wstring& name, IEngineFactoryD3D11* factory,
+                                            IRenderDevice* device, IDeviceContext* context,
+                                            const std::optional<std::string>& shaders)
+    {
+        std::unique_ptr<ViewWindow> view(new ViewWindow());
+        view->name_ = narrow(name.substr(name.rfind(L'-') + 1));
+        view->mapping_ = OpenFileMappingW(FILE_MAP_ALL_ACCESS, FALSE, name.c_str());
+        if (view->mapping_ == nullptr) {
+            return nullptr; // its engine is gone already
+        }
+        view->channel_ = static_cast<Channel*>(MapViewOfFile(view->mapping_, FILE_MAP_ALL_ACCESS, 0, 0, 0));
+        view->ready_ = OpenEventW(SYNCHRONIZE, FALSE, (name + t5de::protocol::readyEventSuffix).c_str());
+        view->consumed_ = OpenEventW(EVENT_MODIFY_STATE, FALSE, (name + t5de::protocol::consumedEventSuffix).c_str());
+        view->read_ = OpenEventW(EVENT_MODIFY_STATE, FALSE, (name + t5de::protocol::readEventSuffix).c_str());
+        if (view->channel_ == nullptr || view->ready_ == nullptr || view->consumed_ == nullptr
+            || view->read_ == nullptr || view->channel_->version != t5de::protocol::version) {
+            info("{}: can't open the channel", view->name_);
+            return nullptr;
+        }
+        view->data_ = reinterpret_cast<std::byte*>(view->channel_ + 1);
+        view->clientWindow_ = reinterpret_cast<HWND>(static_cast<std::uintptr_t>(view->channel_->window));
+        view->window_ = create_child_window(view->clientWindow_);
+        if (view->window_ == nullptr) {
+            info("{}: can't create a window in {:#x}", view->name_, view->channel_->window);
+            return nullptr;
+        }
+        SwapChainDesc swapChainDesc;
+        swapChainDesc.ColorBufferFormat = TEX_FORMAT_RGBA8_UNORM; // no sRGB conversion, like the client's renderer
+        swapChainDesc.DepthBufferFormat = TEX_FORMAT_D32_FLOAT;
+        factory->CreateSwapChainD3D11(device, context, swapChainDesc, FullScreenModeDesc{},
+                                      Win32NativeWindow{view->window_}, &view->swapChain_);
+        if (!view->swapChain_) {
+            info("{}: can't create a swap chain", view->name_);
+            return nullptr;
+        }
+        view->scene_ = std::make_unique<t5de::Scene>(device, context, view->swapChain_);
+        if (shaders) {
+            view->scene_->setShaderSource(*shaders);
+        }
+        // Frames read back: the adapter waits for them, sending nothing meanwhile, so the data area is free.
+        ViewWindow* self = view.get();
+        view->scene_->setReadBack([self](std::span<const std::byte> pixels) {
+            const std::size_t size = pixels.size() <= self->channel_->capacity ? pixels.size() : 0;
+            std::memcpy(self->data_, pixels.data(), size);
+            self->channel_->readSize = static_cast<std::uint32_t>(size);
+            SetEvent(self->read_);
+        });
+        QueryPerformanceFrequency(&view->frequency_);
+        view->framesReady_ = CreateEventW(nullptr, FALSE, FALSE, nullptr);
+        if (view->framesReady_ == nullptr) {
+            return nullptr;
+        }
+        view->receiver_ = std::thread([self] { self->receive(); });
+        info("{}: drawing window {:#x}, view {}", view->name_, view->channel_->window,
+             static_cast<int>(view->channel_->view));
+        return view;
+    }
+
+    ViewWindow(const ViewWindow&) = delete;
+    ViewWindow& operator=(const ViewWindow&) = delete;
+
+    ~ViewWindow()
+    {
+        stopping_ = true;
+        if (receiver_.joinable()) {
+            receiver_.join();
+        }
+        if (channel_ != nullptr) {
+            channel_->covering = 0;
+            UnmapViewOfFile(channel_);
+        }
+        scene_.reset();
+        swapChain_.Release();
+        if (window_ != nullptr) {
+            DestroyWindow(window_);
+            info("{}: closed", name_);
+        }
+        for (HANDLE handle : {ready_, consumed_, read_, mapping_, framesReady_}) {
+            if (handle != nullptr) {
+                CloseHandle(handle);
+            }
+        }
+    }
+
+    // Set when complete frames are queued.
+    [[nodiscard]] HANDLE framesReady() const { return framesReady_; }
+    // Its engine is gone.
+    [[nodiscard]] bool closing() const { return channel_->closing != 0; }
+
+    void setShaderSource(const std::string& source) { scene_->setShaderSource(source); }
+
+    // After framesReady: draws the newest complete frame queued. If the client has sent more meanwhile (drawing fell
+    // behind), the older ones' changes are carried out without drawing them.
+    void onFramesReady()
+    {
+        std::vector<std::size_t> ends;
+        {
+            const std::scoped_lock lock(mutex_);
+            if (frameEnds_.empty()) {
+                return;
+            }
+            const std::size_t complete = frameEnds_.back();
+            frame_.assign(received_.begin(), received_.begin() + static_cast<std::ptrdiff_t>(complete));
+            received_.erase(received_.begin(), received_.begin() + static_cast<std::ptrdiff_t>(complete));
+            ends.swap(frameEnds_);
+        }
+        std::size_t begin = 0;
+        for (std::size_t i = 0; i + 1 < ends.size(); ++i) {
+            scene_->execute(std::span(frame_).subspan(begin, ends[i] - begin), 0, false);
+            begin = ends[i];
+            ++skipped_;
+        }
+        const std::size_t complete = ends.back();
+
+        // Follow the client's 3D view's size.
+        const View view = current_view(channel_->view);
+        const auto [place, offset] = placement(clientWindow_, view);
+        const int width = place.right - place.left;
+        const int height = place.bottom - place.top;
+        if (std::memcmp(&place, &placed_, sizeof(RECT)) != 0) {
+            placed_ = place;
+            if (width > 0 && height > 0) {
+                SetWindowPos(window_, nullptr, place.left, place.top, width, height,
+                             SWP_NOZORDER | SWP_NOACTIVATE | SWP_SHOWWINDOW);
+                swapChain_->Resize(static_cast<Uint32>(width), static_cast<Uint32>(height));
+                info("{}: drawing {}x{} at {} in the client's 3D view, its scene from {}", name_, width, height,
+                     place.left, offset);
+            } else {
+                ShowWindow(window_, SW_HIDE);
+                channel_->covering = 0;
+                info("{}: hidden", name_);
+            }
+        }
+        LARGE_INTEGER start, end;
+        QueryPerformanceCounter(&start);
+        const bool covers = view == View::Full && width > 0 && height > 0;
+        if (scene_->execute(std::span(frame_).subspan(begin, complete - begin), offset, width > 0 && height > 0)) {
+            swapChain_->Present(0);
+            channel_->covering = covers ? 1 : 0; // the client's renderer can stop drawing (or must start again)
+            QueryPerformanceCounter(&end);
+            const auto seconds = [this](LONGLONG ticks) {
+                return static_cast<double>(ticks) / static_cast<double>(frequency_.QuadPart);
+            };
+            drawTime_ += seconds(end.QuadPart - start.QuadPart);
+            latency_ += seconds(end.QuadPart - static_cast<LONGLONG>(scene_->lastSentAt()));
+            if (++drawn_ == 300) {
+                info("{}: last 300 frames: {:.1f} ms each to draw and present, {:.1f} ms from the client's end of frame "
+                     "to presented, {} skipped to catch up",
+                     name_, drawTime_ * 1000 / drawn_, latency_ * 1000 / drawn_, skipped_);
+                drawTime_ = 0;
+                latency_ = 0;
+                drawn_ = 0;
+                skipped_ = 0;
+            }
+        }
+    }
+
+private:
+    ViewWindow() = default;
+
+    // The receiver thread: takes each chunk as it comes (after "ready"), lets the adapter send the next, and queues it;
+    // sets framesReady when a frame is complete. Ends when the view closes.
+    void receive()
+    {
+        while (!stopping_ && !closing()) {
+            if (WaitForSingleObject(ready_, 100) != WAIT_OBJECT_0 || closing()) {
+                continue;
+            }
+            const std::uint32_t size = channel_->chunkSize <= channel_->capacity ? channel_->chunkSize : 0;
+            const bool endsFrame = (channel_->chunkFlags & t5de::protocol::chunkEndsFrame) != 0;
+            {
+                const std::scoped_lock lock(mutex_);
+                received_.insert(received_.end(), data_, data_ + size);
+                if (endsFrame) {
+                    frameEnds_.push_back(received_.size());
+                }
+            }
+            SetEvent(consumed_);
+            if (endsFrame) {
+                SetEvent(framesReady_);
+            }
+        }
+        SetEvent(framesReady_); // wakes the main thread to close the view
+    }
+
+    std::string name_;
+    HANDLE mapping_ = nullptr;
+    HANDLE ready_ = nullptr;
+    HANDLE consumed_ = nullptr;
+    HANDLE read_ = nullptr;
+    Channel* channel_ = nullptr;
+    std::byte* data_ = nullptr;
+    HWND clientWindow_ = nullptr;
+    HWND window_ = nullptr;
+    RefCntAutoPtr<ISwapChain> swapChain_;
+    std::unique_ptr<t5de::Scene> scene_;
+    std::vector<std::byte> frame_; // the frames being drawn
+    RECT placed_{};
+
+    std::thread receiver_;
+    std::atomic<bool> stopping_ = false;
+    HANDLE framesReady_ = nullptr;
+    std::mutex mutex_;                  // guards received_ and frameEnds_
+    std::vector<std::byte> received_;   // chunks taken, not yet drawn
+    std::vector<std::size_t> frameEnds_; // where complete frames end in received_
+
+    LARGE_INTEGER frequency_{};
+    double drawTime_ = 0;
+    double latency_ = 0;
+    int drawn_ = 0;
+    int skipped_ = 0;
+};
+
+} // namespace
+
+int WINAPI wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
+{
+    const Arguments arguments = parse_arguments();
+    if (arguments.control.empty()) {
+        return 2;
+    }
+    HANDLE mapping = OpenFileMappingW(FILE_MAP_READ, FALSE, arguments.control.c_str());
+    const auto* control = mapping == nullptr ? nullptr
+                                             : static_cast<const t5de::protocol::Control*>(
+                                                   MapViewOfFile(mapping, FILE_MAP_READ, 0, 0, 0));
+    HANDLE attach = OpenEventW(SYNCHRONIZE, FALSE, (arguments.control + t5de::protocol::attachEventSuffix).c_str());
+    HANDLE parent = OpenProcess(SYNCHRONIZE, FALSE, arguments.parent);
+    if (control == nullptr || attach == nullptr || parent == nullptr || control->version != t5de::protocol::version) {
+        return 3;
+    }
+
+    info("started for client {}", arguments.parent);
+    IEngineFactoryD3D11* factory = GetEngineFactoryD3D11();
+    factory->SetMessageCallback(diligent_message);
+    RefCntAutoPtr<IRenderDevice> device;
+    RefCntAutoPtr<IDeviceContext> context;
+    EngineD3D11CreateInfo engineInfo;
+    factory->CreateDeviceAndContextsD3D11(engineInfo, &device, &context);
+    if (!device) {
+        info("can't create a Direct3D 11 device");
+        return 5;
+    }
+    // Show each frame as soon as it's drawn: Direct3D 11 otherwise lets 3 frames queue, which the view would trail by.
+    if (RefCntAutoPtr<IRenderDeviceD3D11> d3d11{device, IID_RenderDeviceD3D11}) {
+        IDXGIDevice1* dxgi = nullptr;
+        if (SUCCEEDED(d3d11->GetD3D11Device()->QueryInterface(__uuidof(IDXGIDevice1), reinterpret_cast<void**>(&dxgi)))) {
+            dxgi->SetMaximumFrameLatency(1);
+            dxgi->Release();
+        }
+    }
+
+    std::vector<std::unique_ptr<ViewWindow>> views;
+    std::uint32_t attached = 0;
+    std::optional<std::string> shaders; // the override, if any
+    std::size_t first = 0;              // which view's event is waited on first, taking turns
+    for (;;) {
+        // New channels: opened in order; those whose engines are gone already are skipped.
+        while (attached < control->channels) {
+            if (auto view = ViewWindow::open(std::format(L"{}-{}", arguments.control, attached), factory, device,
+                                             context, shaders)) {
+                views.push_back(std::move(view));
+            }
+            ++attached;
+        }
+        std::erase_if(views, [](const auto& view) { return view->closing(); });
+        if (auto source = changed_shaders()) {
+            shaders = std::move(source);
+            for (const auto& view : views) {
+                view->setShaderSource(*shaders);
+            }
+        }
+
+        std::vector<HANDLE> handles{parent, attach};
+        const std::size_t count = std::min<std::size_t>(views.size(), MAXIMUM_WAIT_OBJECTS - 3);
+        for (std::size_t i = 0; i < count; ++i) {
+            handles.push_back(views[(first + i) % views.size()]->framesReady());
+        }
+        const DWORD result = MsgWaitForMultipleObjects(static_cast<DWORD>(handles.size()), handles.data(), FALSE, 1000,
+                                                       QS_ALLINPUT);
+        MSG message;
+        while (PeekMessageW(&message, nullptr, 0, 0, PM_REMOVE)) {
+            DispatchMessageW(&message);
+        }
+        if (result == WAIT_OBJECT_0) {
+            break; // the client exited
+        }
+        if (result >= WAIT_OBJECT_0 + 2 && result < WAIT_OBJECT_0 + handles.size()) {
+            const std::size_t index = (first + (result - WAIT_OBJECT_0 - 2)) % views.size();
+            views[index]->onFramesReady();
+            first = (index + 1) % views.size();
+        }
+    }
+
+    views.clear();
+    info("exiting");
+    return 0;
+}

renderer/scene.cpp

@@ -0,0 +1,806 @@
+#include "scene.hpp"
+
+#include <cstring>
+#include <string>
+
+#include "fixed_function_hlsl.hpp"
+
+namespace t5de {
+
+using namespace Diligent;
+using protocol::Op;
+
+namespace {
+
+void set_identity(float (&m)[16])
+{
+    std::memset(m, 0, sizeof(m));
+    m[0] = m[5] = m[10] = m[15] = 1;
+}
+
+// An affine transform (3x3 row-major, then translation) as a 4x4 matrix for row vectors.
+void set_transform(float (&m)[16], const float (&t)[12])
+{
+    for (int row = 0; row < 3; ++row) {
+        m[row * 4 + 0] = t[row * 3 + 0];
+        m[row * 4 + 1] = t[row * 3 + 1];
+        m[row * 4 + 2] = t[row * 3 + 2];
+        m[row * 4 + 3] = 0;
+    }
+    m[12] = t[9];
+    m[13] = t[10];
+    m[14] = t[11];
+    m[15] = 1;
+}
+
+// u' = u * m[0] + v * m[1] + m[4], v' = u * m[2] + v * m[3] + m[5], as two rows dotted with (u, v, 1).
+void set_texture_transform(float (&rows)[8], const float (&m)[6])
+{
+    const float values[8] = {m[0], m[1], m[4], 0, m[2], m[3], m[5], 0};
+    std::memcpy(rows, values, sizeof(rows));
+}
+
+void set_color(float (&rgba)[4], std::uint32_t color)
+{
+    rgba[0] = static_cast<float>((color >> 16) & 0xff) / 255.0f;
+    rgba[1] = static_cast<float>((color >> 8) & 0xff) / 255.0f;
+    rgba[2] = static_cast<float>(color & 0xff) / 255.0f;
+    rgba[3] = static_cast<float>(color >> 24) / 255.0f;
+}
+
+constexpr std::uint32_t hasNormals = 1;
+constexpr std::uint32_t hasTexCoords = 2;
+constexpr std::uint32_t hasColors = 4;
+
+} // namespace
+
+Scene::Scene(IRenderDevice* device, IDeviceContext* context, ISwapChain* swapChain)
+    : device_(device), context_(context), swapChain_(swapChain), shaderSource_(fixedFunctionHlsl)
+{
+    BufferDesc constants;
+    constants.Name = "Constants";
+    constants.Size = sizeof(Constants);
+    constants.Usage = USAGE_DYNAMIC;
+    constants.BindFlags = BIND_UNIFORM_BUFFER;
+    constants.CPUAccessFlags = CPU_ACCESS_WRITE;
+    device_->CreateBuffer(constants, nullptr, &constantBuffer_);
+
+    // IMVU's textures: bilinear, no mipmaps, wrapped or clamped per texture.
+    for (int wrap = 0; wrap < 4; ++wrap) {
+        SamplerDesc sampler;
+        sampler.MinFilter = FILTER_TYPE_LINEAR;
+        sampler.MagFilter = FILTER_TYPE_LINEAR;
+        sampler.MipFilter = FILTER_TYPE_POINT;
+        sampler.AddressU = (wrap & 1) != 0 ? TEXTURE_ADDRESS_WRAP : TEXTURE_ADDRESS_CLAMP;
+        sampler.AddressV = (wrap & 2) != 0 ? TEXTURE_ADDRESS_WRAP : TEXTURE_ADDRESS_CLAMP;
+        device_->CreateSampler(sampler, &samplers_[wrap]);
+    }
+
+    set_identity(constants_.world);
+    set_identity(constants_.view);
+    set_identity(constants_.projection);
+    const float identity[6] = {1, 0, 0, 1, 0, 0};
+    set_texture_transform(constants_.texTransform0, identity);
+    set_texture_transform(constants_.texTransform1, identity);
+    constants_.flags[2] = 127; // the client's alpha reference
+}
+
+void Scene::setShaderSource(std::string source)
+{
+    shaderSource_ = std::move(source);
+    shaders_.clear();
+    pipelines_.clear();
+}
+
+bool Scene::execute(std::span<const std::byte> commands, int offsetX, bool draw)
+{
+    offsetX_ = offsetX;
+    draw_ = draw;
+    bool drew = false;
+    protocol::Reader reader(commands);
+    while (const auto command = reader.next()) {
+        switch (command->op()) {
+        case Op::BeginFrame:
+            if (const auto begin = command->body<protocol::BeginFrame>()) {
+                beginFrame(*begin);
+            }
+            break;
+        case Op::EndFrame:
+            if (const auto end = command->body<protocol::EndFrame>()) {
+                lastSentAt_ = end->sentAt;
+            }
+            drew = drew || onscreen_;
+            endFrame();
+            break;
+        case Op::Clear:
+            if (const auto clear = command->body<protocol::Clear>(); clear && colorView_ != nullptr) {
+                if ((clear->flags & 1) != 0) {
+                    float color[4];
+                    set_color(color, clear->color);
+                    context_->ClearRenderTarget(colorView_, color, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+                }
+                if ((clear->flags & 2) != 0) {
+                    context_->ClearDepthStencil(depthView_, CLEAR_DEPTH_FLAG, 1.0f, 0,
+                                                RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+                }
+            }
+            break;
+        case Op::SetProjection:
+            if (const auto projection = command->body<protocol::SetProjection>()) {
+                setProjection(*projection);
+            }
+            break;
+        case Op::SetModel:
+            if (const auto model = command->body<protocol::SetTransform>()) {
+                set_transform(constants_.world, model->m);
+            }
+            break;
+        case Op::SetView:
+            if (const auto view = command->body<protocol::SetTransform>()) {
+                set_transform(constants_.view, view->m);
+            }
+            break;
+        case Op::SetTextures:
+            if (const auto textures = command->body<protocol::SetTextures>()) {
+                state_.texture0 = textures->texture0;
+                state_.texture1 = textures->texture1;
+            }
+            break;
+        case Op::SetState:
+            if (const auto state = command->body<protocol::SetState>()) {
+                setState(*state);
+            }
+            break;
+        case Op::SetLight:
+            if (const auto light = command->body<protocol::SetLight>(); light && light->index < 8) {
+                set_color(constants_.lightColor[light->index], light->color);
+                constants_.lightColor[light->index][3] = light->enabled != 0 ? 1.0f : 0.0f;
+                std::memcpy(constants_.lightVector[light->index], light->vector, sizeof(light->vector));
+                constants_.lightVector[light->index][3] = light->directional != 0 ? 1.0f : 0.0f;
+            }
+            break;
+        case Op::SetFog:
+            if (const auto fog = command->body<protocol::SetFog>()) {
+                constants_.fog[0] = fog->start;
+                constants_.fog[1] = fog->end;
+                set_color(constants_.fogColor, fog->color);
+            }
+            break;
+        case Op::SetTextureTransform:
+            if (const auto transform = command->body<protocol::SetTextureTransform>(); transform && transform->stage < 2) {
+                set_texture_transform(transform->stage == 0 ? constants_.texTransform0 : constants_.texTransform1,
+                                      transform->m);
+            }
+            break;
+        case Op::CreateTexture:
+            createTexture(*command);
+            break;
+        case Op::UpdateTexture:
+            updateTexture(*command);
+            break;
+        case Op::CreateRenderTarget:
+            if (const auto create = command->body<protocol::CreateRenderTarget>()) {
+                createRenderTarget(*create);
+            }
+            break;
+        case Op::DestroyTexture:
+            if (const auto destroy = command->body<protocol::DestroyTexture>()) {
+                textures_.erase(destroy->id);
+            }
+            break;
+        case Op::CreateBuffer:
+            createBuffer(*command);
+            break;
+        case Op::UpdateBuffer:
+            updateBuffer(*command);
+            break;
+        case Op::DestroyBuffer:
+            if (const auto destroy = command->body<protocol::DestroyBuffer>()) {
+                buffers_.erase(destroy->id);
+            }
+            break;
+        case Op::DrawTriangles:
+            if (const auto triangles = command->body<protocol::DrawTriangles>(); triangles && colorView_ != nullptr) {
+                drawTriangles(*triangles);
+            }
+            break;
+        case Op::DrawArrays:
+            if (colorView_ != nullptr) {
+                drawArrays(*command);
+            }
+            break;
+        case Op::DrawPointSprites:
+            if (colorView_ != nullptr) {
+                drawPointSprites(*command);
+            }
+            break;
+        }
+    }
+    return drew;
+}
+
+void Scene::setProjection(const protocol::SetProjection& projection)
+{
+    std::memcpy(constants_.projection, projection.m, sizeof(constants_.projection));
+    // The client's projections give depth from -1 to 1, as OpenGL does; IMVU's Direct3D renderer maps it to 0 to 1
+    // (z' = z / 2 + w / 2) before setting them, and so do we. (It also shifts them half a pixel, which Direct3D 9
+    // needs and Direct3D 11 doesn't.)
+    for (int row = 0; row < 4; ++row) {
+        float* m = constants_.projection + row * 4;
+        m[2] = 0.5f * m[2] + 0.5f * m[3];
+    }
+    constants_.viewport[0] = static_cast<float>(projection.width);
+    constants_.viewport[1] = static_cast<float>(projection.height);
+    projectionWidth_ = projection.width;
+    projectionHeight_ = projection.height;
+    setViewport();
+}
+
+void Scene::setViewport()
+{
+    if (colorView_ == nullptr || projectionWidth_ <= 0 || projectionHeight_ <= 0) {
+        return;
+    }
+    // The client's projection covers its whole 3D view; the window shows part of it, from offsetX.
+    const SwapChainDesc& window = swapChain_->GetDesc();
+    Viewport viewport;
+    viewport.TopLeftX = onscreen_ ? static_cast<float>(-offsetX_) : 0.0f;
+    viewport.TopLeftY = 0;
+    viewport.Width = static_cast<float>(projectionWidth_);
+    viewport.Height = static_cast<float>(projectionHeight_);
+    viewport.MinDepth = 0;
+    viewport.MaxDepth = 1;
+    context_->SetViewports(1, &viewport, onscreen_ ? window.Width : target_->width,
+                           onscreen_ ? window.Height : target_->height);
+}
+
+void Scene::beginFrame(const protocol::BeginFrame& begin)
+{
+    onscreen_ = false;
+    target_ = nullptr;
+    colorView_ = nullptr;
+    depthView_ = nullptr;
+    readsBack_ = begin.readBack != 0;
+    if (begin.target == 0) {
+        if (draw_) {
+            onscreen_ = true;
+            colorView_ = swapChain_->GetCurrentBackBufferRTV();
+            depthView_ = swapChain_->GetDepthBufferDSV();
+        }
+    } else if (const auto found = textures_.find(begin.target); found != textures_.end() && found->second.depth) {
+        target_ = &found->second;
+        colorView_ = target_->texture->GetDefaultView(TEXTURE_VIEW_RENDER_TARGET);
+        depthView_ = target_->depth->GetDefaultView(TEXTURE_VIEW_DEPTH_STENCIL);
+    }
+    if (colorView_ != nullptr) {
+        context_->SetRenderTargets(1, &colorView_, depthView_, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+        setViewport();
+    }
+}
+
+void Scene::endFrame()
+{
+    if (readsBack_ && readBack_) {
+        readBack_(target_ != nullptr ? readTarget(*target_) : std::span<const std::byte>{});
+    }
+    if (target_ != nullptr) {
+        // Unbound, so it can be drawn with (a texture can't be both).
+        context_->SetRenderTargets(0, nullptr, nullptr, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+    }
+    onscreen_ = false;
+    target_ = nullptr;
+    readsBack_ = false;
+    colorView_ = nullptr;
+    depthView_ = nullptr;
+}
+
+std::span<const std::byte> Scene::readTarget(const Texture& target)
+{
+    TextureDesc desc;
+    desc.Name = "Render target read back";
+    desc.Type = RESOURCE_DIM_TEX_2D;
+    desc.Width = target.width;
+    desc.Height = target.height;
+    desc.MipLevels = 1;
+    desc.Format = TEX_FORMAT_RGBA8_UNORM;
+    desc.Usage = USAGE_STAGING;
+    desc.CPUAccessFlags = CPU_ACCESS_READ;
+    RefCntAutoPtr<ITexture> staging;
+    device_->CreateTexture(desc, nullptr, &staging);
+    if (!staging) {
+        return {};
+    }
+    CopyTextureAttribs copy(target.texture, RESOURCE_STATE_TRANSITION_MODE_TRANSITION, staging,
+                            RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+    context_->CopyTexture(copy);
+    MappedTextureSubresource mapped;
+    context_->MapTextureSubresource(staging, 0, 0, MAP_READ, MAP_FLAG_NONE, nullptr, mapped); // waits for the GPU
+    if (mapped.pData == nullptr) {
+        return {};
+    }
+    // RGBA in memory, to the client's 0xAARRGGBB (BGRA in memory).
+    readPixels_.resize(std::size_t{target.width} * target.height * 4);
+    for (std::uint32_t y = 0; y < target.height; ++y) {
+        const auto* from = static_cast<const std::uint8_t*>(mapped.pData) + y * mapped.Stride;
+        auto* to = reinterpret_cast<std::uint8_t*>(readPixels_.data()) + std::size_t{y} * target.width * 4;
+        for (std::uint32_t x = 0; x < target.width; ++x) {
+            to[x * 4 + 0] = from[x * 4 + 2];
+            to[x * 4 + 1] = from[x * 4 + 1];
+            to[x * 4 + 2] = from[x * 4 + 0];
+            to[x * 4 + 3] = from[x * 4 + 3];
+        }
+    }
+    context_->UnmapTextureSubresource(staging, 0, 0);
+    return readPixels_;
+}
+
+void Scene::setState(const protocol::SetState& state)
+{
+    const bool on = state.value != 0;
+    switch (state.state) {
+    case protocol::State::DepthTest:
+        state_.depthTest = on;
+        break;
+    case protocol::State::DepthWrite:
+        state_.depthWrite = on;
+        break;
+    case protocol::State::Blending:
+        state_.blending = on;
+        break;
+    case protocol::State::BlendMode:
+        if (state.value >= 1 && state.value <= 4) {
+            state_.blendMode = state.value;
+        }
+        break;
+    case protocol::State::AlphaTest:
+        constants_.flags[1] = on ? 1.0f : 0.0f;
+        break;
+    case protocol::State::AlphaReference:
+        constants_.flags[2] = static_cast<float>(state.value);
+        break;
+    case protocol::State::Culling:
+        state_.culling = on;
+        break;
+    case protocol::State::NormalInverting:
+        state_.normalInverting = on;
+        break;
+    case protocol::State::Lighting:
+        constants_.flags[0] = on ? 1.0f : 0.0f;
+        break;
+    case protocol::State::Fog:
+        constants_.fog[2] = on ? 1.0f : 0.0f;
+        break;
+    case protocol::State::Ambient:
+        set_color(constants_.ambient, state.value);
+        break;
+    }
+}
+
+void Scene::createTexture(const protocol::Command& command)
+{
+    const auto create = command.body<protocol::CreateTexture>();
+    const auto pixels = command.payload<protocol::CreateTexture>();
+    if (!create || create->width == 0 || create->height == 0
+        || pixels.size() < std::size_t{create->width} * create->height * 4) {
+        return;
+    }
+    TextureDesc desc;
+    desc.Name = "Client texture";
+    desc.Type = RESOURCE_DIM_TEX_2D;
+    desc.Width = create->width;
+    desc.Height = create->height;
+    desc.MipLevels = 1;
+    desc.Format = TEX_FORMAT_BGRA8_UNORM; // 0xAARRGGBB in memory
+    desc.BindFlags = BIND_SHADER_RESOURCE;
+    desc.Usage = USAGE_DEFAULT;
+    TextureSubResData level;
+    level.pData = pixels.data();
+    level.Stride = std::uint64_t{create->width} * 4;
+    TextureData data;
+    data.pSubResources = &level;
+    data.NumSubresources = 1;
+    Texture texture{.width = create->width, .height = create->height, .flags = create->flags};
+    device_->CreateTexture(desc, &data, &texture.texture);
+    if (!texture.texture) {
+        return;
+    }
+    texture.texture->GetDefaultView(TEXTURE_VIEW_SHADER_RESOURCE)
+        ->SetSampler(samplers_[((create->flags & 2) != 0 ? 1 : 0) | ((create->flags & 4) != 0 ? 2 : 0)]);
+    textures_[create->id] = std::move(texture);
+}
+
+void Scene::createRenderTarget(const protocol::CreateRenderTarget& create)
+{
+    if (create.width == 0 || create.height == 0) {
+        return;
+    }
+    // The window's formats, so the same pipelines draw into both.
+    const SwapChainDesc& window = swapChain_->GetDesc();
+    TextureDesc desc;
+    desc.Name = "Client render target";
+    desc.Type = RESOURCE_DIM_TEX_2D;
+    desc.Width = create.width;
+    desc.Height = create.height;
+    desc.MipLevels = 1;
+    desc.Format = window.ColorBufferFormat;
+    desc.BindFlags = BIND_RENDER_TARGET | BIND_SHADER_RESOURCE;
+    desc.ClearValue.Format = desc.Format;
+    Texture target{.width = create.width, .height = create.height, .flags = 0};
+    device_->CreateTexture(desc, nullptr, &target.texture);
+    TextureDesc depth = desc;
+    depth.Name = "Client render target depth";
+    depth.Format = window.DepthBufferFormat;
+    depth.BindFlags = BIND_DEPTH_STENCIL;
+    depth.ClearValue.Format = depth.Format;
+    depth.ClearValue.DepthStencil.Depth = 1;
+    device_->CreateTexture(depth, nullptr, &target.depth);
+    if (!target.texture || !target.depth) {
+        return;
+    }
+    target.texture->GetDefaultView(TEXTURE_VIEW_SHADER_RESOURCE)->SetSampler(samplers_[0]);
+    textures_[create.id] = std::move(target);
+}
+
+void Scene::updateTexture(const protocol::Command& command)
+{
+    const auto update = command.body<protocol::UpdateTexture>();
+    const auto pixels = command.payload<protocol::UpdateTexture>();
+    if (!update || pixels.size() < std::size_t{update->width} * update->height * 4) {
+        return;
+    }
+    const auto found = textures_.find(update->id);
+    if (found == textures_.end()) {
+        return;
+    }
+    Texture& texture = found->second;
+    if (texture.width != update->width || texture.height != update->height) {
+        // A different size: make it again, keeping its sampling.
+        protocol::Writer writer;
+        std::memcpy(writer.add(Op::CreateTexture,
+                               protocol::CreateTexture{update->id, update->width, update->height, texture.flags},
+                               pixels.size()),
+                    pixels.data(), pixels.size());
+        protocol::Reader reader(writer.bytes());
+        createTexture(*reader.next());
+        return;
+    }
+    Box box;
+    box.MaxX = update->width;
+    box.MaxY = update->height;
+    TextureSubResData level;
+    level.pData = pixels.data();
+    level.Stride = std::uint64_t{update->width} * 4;
+    context_->UpdateTexture(texture.texture, 0, 0, box, level, RESOURCE_STATE_TRANSITION_MODE_TRANSITION,
+                            RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+}
+
+void Scene::createBuffer(const protocol::Command& command)
+{
+    const auto create = command.body<protocol::CreateBuffer>();
+    if (!create || create->count == 0 || create->elementSize == 0) {
+        return;
+    }
+    const std::size_t size = std::size_t{create->elementSize} * create->count;
+    const auto contents = command.payload<protocol::CreateBuffer>();
+    const bool filled = contents.size() >= size;
+    BufferDesc desc;
+    desc.Name = create->kind == protocol::BufferKind::Index ? "Client indices" : "Client vertices";
+    desc.Size = size;
+    desc.BindFlags = create->kind == protocol::BufferKind::Index ? BIND_INDEX_BUFFER : BIND_VERTEX_BUFFER;
+    desc.Usage = filled ? USAGE_IMMUTABLE : USAGE_DEFAULT; // dynamic buffers are filled by updates
+    BufferData data;
+    data.pData = contents.data();
+    data.DataSize = size;
+    Buffer buffer{.kind = create->kind, .elementSize = create->elementSize, .count = create->count};
+    device_->CreateBuffer(desc, filled ? &data : nullptr, &buffer.buffer);
+    if (buffer.buffer) {
+        buffers_[create->id] = std::move(buffer);
+    }
+}
+
+void Scene::updateBuffer(const protocol::Command& command)
+{
+    const auto update = command.body<protocol::UpdateBuffer>();
+    const auto contents = command.payload<protocol::UpdateBuffer>();
+    if (!update) {
+        return;
+    }
+    const auto found = buffers_.find(update->id);
+    const std::size_t size = std::size_t{update->elementSize} * update->count;
+    if (found == buffers_.end() || contents.size() < size || found->second.elementSize != update->elementSize
+        || found->second.count != update->count || found->second.buffer->GetDesc().Usage != USAGE_DEFAULT) {
+        return;
+    }
+    context_->UpdateBuffer(found->second.buffer, 0, size, contents.data(), RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+}
+
+ITextureView* Scene::textureView(std::uint32_t id)
+{
+    const auto found = textures_.find(id);
+    return found == textures_.end() ? nullptr : found->second.texture->GetDefaultView(TEXTURE_VIEW_SHADER_RESOURCE);
+}
+
+void Scene::drawTriangles(const protocol::DrawTriangles& draw)
+{
+    const auto buffer = [this](std::uint32_t id, protocol::BufferKind kind, std::uint32_t elementSize) -> Buffer* {
+        const auto found = buffers_.find(id);
+        if (id == 0 || found == buffers_.end() || found->second.kind != kind || found->second.elementSize != elementSize) {
+            return nullptr;
+        }
+        return &found->second;
+    };
+    Buffer* indices = buffer(draw.indices, protocol::BufferKind::Index, 2);
+    Buffer* positions = buffer(draw.positions, protocol::BufferKind::Vertex, 12);
+    if (indices == nullptr || positions == nullptr) {
+        return;
+    }
+    // Optional streams count only if they cover every vertex.
+    const auto optional = [&](std::uint32_t id, std::uint32_t elementSize) -> IBuffer* {
+        Buffer* found = buffer(id, protocol::BufferKind::Vertex, elementSize);
+        return found != nullptr && found->count >= positions->count ? found->buffer.RawPtr() : nullptr;
+    };
+    this->draw(indices->buffer, indices->count, positions->buffer, optional(draw.normals, 12),
+               optional(draw.texCoords, 8), optional(draw.colors, 4));
+}
+
+void Scene::drawArrays(const protocol::Command& command)
+{
+    const auto arrays = command.body<protocol::DrawArrays>();
+    const auto payload = command.payload<protocol::DrawArrays>();
+    if (!arrays || arrays->vertexCount == 0 || arrays->indexCount == 0) {
+        return;
+    }
+    const std::size_t indexBytes = protocol::padded(std::size_t{arrays->indexCount} * 2);
+    const std::size_t vertices = arrays->vertexCount;
+    if (payload.size() < indexBytes + vertices * (12 + (arrays->hasNormals ? 12 : 0) + (arrays->hasTexCoords ? 8 : 0) +
+                                                  (arrays->hasColors ? 4 : 0))) {
+        return;
+    }
+    const auto make = [this](const std::byte* data, std::size_t size, BIND_FLAGS bind) {
+        BufferDesc desc;
+        desc.Name = "Client arrays";
+        desc.Size = size;
+        desc.BindFlags = bind;
+        desc.Usage = USAGE_IMMUTABLE;
+        BufferData contents;
+        contents.pData = data;
+        contents.DataSize = size;
+        RefCntAutoPtr<IBuffer> buffer;
+        device_->CreateBuffer(desc, &contents, &buffer);
+        return buffer;
+    };
+    const std::byte* next = payload.data();
+    const auto indices = make(next, std::size_t{arrays->indexCount} * 2, BIND_INDEX_BUFFER);
+    next += indexBytes;
+    const auto positions = make(next, vertices * 12, BIND_VERTEX_BUFFER);
+    next += vertices * 12;
+    RefCntAutoPtr<IBuffer> normals, texCoords, colors;
+    if (arrays->hasNormals) {
+        normals = make(next, vertices * 12, BIND_VERTEX_BUFFER);
+        next += vertices * 12;
+    }
+    if (arrays->hasTexCoords) {
+        texCoords = make(next, vertices * 8, BIND_VERTEX_BUFFER);
+        next += vertices * 8;
+    }
+    if (arrays->hasColors) {
+        colors = make(next, vertices * 4, BIND_VERTEX_BUFFER);
+    }
+    draw(indices, arrays->indexCount, positions, normals, texCoords, colors);
+}
+
+void Scene::draw(IBuffer* indices, std::uint32_t indexCount, IBuffer* positions, IBuffer* normals, IBuffer* texCoords,
+                 IBuffer* colors)
+{
+    if (indices == nullptr || positions == nullptr || indexCount == 0) {
+        return;
+    }
+    const std::uint32_t streams =
+        (normals != nullptr ? hasNormals : 0) | (texCoords != nullptr ? hasTexCoords : 0) | (colors != nullptr ? hasColors : 0);
+    if (prepare(streams, false) == nullptr) {
+        return;
+    }
+
+    IBuffer* vertexBuffers[4];
+    std::uint32_t count = 0;
+    for (IBuffer* stream : {positions, normals, texCoords, colors}) {
+        if (stream != nullptr) {
+            vertexBuffers[count++] = stream;
+        }
+    }
+    context_->SetVertexBuffers(0, count, vertexBuffers, nullptr, RESOURCE_STATE_TRANSITION_MODE_TRANSITION,
+                               SET_VERTEX_BUFFERS_FLAG_RESET);
+    context_->SetIndexBuffer(indices, 0, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+    DrawIndexedAttribs attributes;
+    attributes.NumIndices = indexCount;
+    attributes.IndexType = VT_UINT16;
+    context_->DrawIndexed(attributes);
+}
+
+Scene::Pipeline* Scene::prepare(std::uint32_t streams, bool sprites)
+{
+    // Like the client: no textures, the first, or both (the second only with a first).
+    ITextureView* texture0 = textureView(state_.texture0);
+    ITextureView* texture1 = texture0 != nullptr ? textureView(state_.texture1) : nullptr;
+    const std::uint32_t textures = texture0 == nullptr ? 0 : texture1 == nullptr ? 1 : 2;
+    Pipeline* selected = pipeline(streams, textures, sprites);
+    if (selected == nullptr) {
+        return nullptr;
+    }
+
+    void* mapped = nullptr;
+    context_->MapBuffer(constantBuffer_, MAP_WRITE, MAP_FLAG_DISCARD, mapped);
+    if (mapped == nullptr) {
+        return nullptr;
+    }
+    std::memcpy(mapped, &constants_, sizeof(constants_));
+    context_->UnmapBuffer(constantBuffer_, MAP_WRITE);
+
+    if (selected->texture0 != nullptr) {
+        selected->texture0->Set(texture0);
+    }
+    if (selected->texture1 != nullptr) {
+        selected->texture1->Set(texture1);
+    }
+    context_->SetPipelineState(selected->state);
+    context_->CommitShaderResources(selected->bindings, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+    return selected;
+}
+
+void Scene::drawPointSprites(const protocol::Command& command)
+{
+    const auto sprites = command.body<protocol::DrawPointSprites>();
+    const auto payload = command.payload<protocol::DrawPointSprites>();
+    if (!sprites || sprites->count == 0 || payload.size() < std::size_t{sprites->count} * 16) {
+        return;
+    }
+    BufferDesc desc;
+    desc.Name = "Client particles";
+    desc.Size = std::size_t{sprites->count} * 16;
+    desc.BindFlags = BIND_VERTEX_BUFFER;
+    desc.Usage = USAGE_IMMUTABLE;
+    BufferData contents;
+    contents.pData = payload.data();
+    contents.DataSize = desc.Size;
+    RefCntAutoPtr<IBuffer> buffer;
+    device_->CreateBuffer(desc, &contents, &buffer);
+    if (!buffer || prepare(0, true) == nullptr) {
+        return;
+    }
+    IBuffer* buffers[] = {buffer};
+    context_->SetVertexBuffers(0, 1, buffers, nullptr, RESOURCE_STATE_TRANSITION_MODE_TRANSITION,
+                               SET_VERTEX_BUFFERS_FLAG_RESET);
+    DrawAttribs attributes;
+    attributes.NumVertices = 4;
+    attributes.NumInstances = sprites->count;
+    context_->Draw(attributes);
+}
+
+const Scene::Shaders& Scene::shaders(std::uint32_t streams, std::uint32_t textures, bool sprites)
+{
+    const std::uint32_t key = streams | (textures << 3) | (sprites ? 1u << 5 : 0);
+    if (const auto found = shaders_.find(key); found != shaders_.end()) {
+        return found->second;
+    }
+    const std::string source = std::string("#define HAS_NORMALS ") + ((streams & hasNormals) != 0 ? "1" : "0") +
+                               "\n#define HAS_TEX_COORDS " + ((streams & hasTexCoords) != 0 ? "1" : "0") +
+                               "\n#define HAS_COLORS " + ((streams & hasColors) != 0 ? "1" : "0") +
+                               "\n#define TEXTURES " + std::to_string(textures) + "\n" + shaderSource_;
+    Shaders created;
+    ShaderCreateInfo info;
+    info.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL;
+    info.Desc.UseCombinedTextureSamplers = true; // g_TextureN with g_TextureN_sampler, set from each texture's view
+    info.Source = source.c_str();
+    info.Desc.ShaderType = SHADER_TYPE_VERTEX;
+    info.Desc.Name = sprites ? "Fixed function particles (vertex)" : "Fixed function (vertex)";
+    info.EntryPoint = sprites ? "vs_sprite" : "vs_main";
+    device_->CreateShader(info, &created.vertex);
+    info.Desc.ShaderType = SHADER_TYPE_PIXEL;
+    info.Desc.Name = "Fixed function (pixel)";
+    info.EntryPoint = "ps_main";
+    device_->CreateShader(info, &created.pixel);
+    return shaders_[key] = std::move(created);
+}
+
+Scene::Pipeline* Scene::pipeline(std::uint32_t streams, std::uint32_t textures, bool sprites)
+{
+    const std::uint32_t blend = state_.blending ? state_.blendMode : 0;
+    const bool culling = state_.culling && !sprites; // point sprites aren't culled
+    const std::uint32_t key = streams | (textures << 3) | (blend << 5) | (state_.depthTest ? 1u << 8 : 0) |
+                              (state_.depthWrite ? 1u << 9 : 0) | (culling ? 1u << 10 : 0) |
+                              (state_.normalInverting ? 1u << 11 : 0) | (sprites ? 1u << 12 : 0);
+    if (const auto found = pipelines_.find(key); found != pipelines_.end()) {
+        return found->second.state ? &found->second : nullptr;
+    }
+    Pipeline& entry = pipelines_[key];
+    const Shaders& compiled = shaders(streams, textures, sprites);
+    if (!compiled.vertex || !compiled.pixel) {
+        return nullptr;
+    }
+
+    GraphicsPipelineStateCreateInfo info;
+    info.PSODesc.Name = "Fixed function";
+    info.PSODesc.PipelineType = PIPELINE_TYPE_GRAPHICS;
+    const SwapChainDesc& window = swapChain_->GetDesc();
+    GraphicsPipelineDesc& graphics = info.GraphicsPipeline;
+    graphics.NumRenderTargets = 1;
+    graphics.RTVFormats[0] = window.ColorBufferFormat;
+    graphics.DSVFormat = window.DepthBufferFormat;
+    graphics.PrimitiveTopology = sprites ? PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP : PRIMITIVE_TOPOLOGY_TRIANGLE_LIST;
+    // The client culls clockwise triangles, or counter-clockwise ones when normals are inverted (mirrored objects).
+    graphics.RasterizerDesc.CullMode = culling ? CULL_MODE_BACK : CULL_MODE_NONE;
+    graphics.RasterizerDesc.FrontCounterClockwise = !state_.normalInverting;
+    graphics.DepthStencilDesc.DepthEnable = state_.depthTest;
+    graphics.DepthStencilDesc.DepthWriteEnable = state_.depthWrite;
+    graphics.DepthStencilDesc.DepthFunc = COMPARISON_FUNC_LESS;
+    RenderTargetBlendDesc& blending = graphics.BlendDesc.RenderTargets[0];
+    blending.BlendEnable = blend != 0;
+    if (blend != 0) {
+        const BLEND_FACTOR source = blend == 1 || blend == 4 ? BLEND_FACTOR_SRC_ALPHA : BLEND_FACTOR_ONE;
+        const BLEND_FACTOR destination = blend == 2 || blend == 4 ? BLEND_FACTOR_ONE : BLEND_FACTOR_INV_SRC_ALPHA;
+        blending.SrcBlend = blending.SrcBlendAlpha = source;
+        blending.DestBlend = blending.DestBlendAlpha = destination;
+        blending.BlendOp = blending.BlendOpAlpha = BLEND_OPERATION_ADD;
+    }
+
+    LayoutElement elements[4];
+    std::uint32_t count = 0;
+    if (sprites) {
+        // One buffer of sprites, each a position and a color, read once per square (instance).
+        elements[0] = LayoutElement{0, 0, 3, VT_FLOAT32, False};
+        elements[1] = LayoutElement{3, 0, 4, VT_UINT8, True};
+        elements[1].RelativeOffset = 12;
+        for (LayoutElement& element : std::span(elements).first(2)) {
+            element.Stride = 16;
+            element.Frequency = INPUT_ELEMENT_FREQUENCY_PER_INSTANCE;
+            element.InstanceDataStepRate = 1;
+        }
+        count = 2;
+    } else {
+        elements[count] = LayoutElement{0, count, 3, VT_FLOAT32, False};
+        ++count;
+    }
+    if (!sprites && (streams & hasNormals) != 0) {
+        elements[count] = LayoutElement{1, count, 3, VT_FLOAT32, False};
+        ++count;
+    }
+    if (!sprites && (streams & hasTexCoords) != 0) {
+        elements[count] = LayoutElement{2, count, 2, VT_FLOAT32, False};
+        ++count;
+    }
+    if (!sprites && (streams & hasColors) != 0) {
+        elements[count] = LayoutElement{3, count, 4, VT_UINT8, True};
+        ++count;
+    }
+    graphics.InputLayout.LayoutElements = elements;
+    graphics.InputLayout.NumElements = count;
+
+    info.pVS = compiled.vertex;
+    info.pPS = compiled.pixel;
+    const ShaderResourceVariableDesc variables[] = {
+        {SHADER_TYPE_PIXEL, "g_Texture0", SHADER_RESOURCE_VARIABLE_TYPE_DYNAMIC},
+        {SHADER_TYPE_PIXEL, "g_Texture1", SHADER_RESOURCE_VARIABLE_TYPE_DYNAMIC},
+    };
+    info.PSODesc.ResourceLayout.DefaultVariableType = SHADER_RESOURCE_VARIABLE_TYPE_STATIC;
+    info.PSODesc.ResourceLayout.Variables = variables;
+    info.PSODesc.ResourceLayout.NumVariables = textures;
+    device_->CreateGraphicsPipelineState(info, &entry.state);
+    if (!entry.state) {
+        return nullptr;
+    }
+    for (const SHADER_TYPE stage : {SHADER_TYPE_VERTEX, SHADER_TYPE_PIXEL}) {
+        if (IShaderResourceVariable* constants = entry.state->GetStaticVariableByName(stage, "Constants")) {
+            constants->Set(constantBuffer_);
+        }
+    }
+    entry.state->CreateShaderResourceBinding(&entry.bindings, true);
+    if (textures >= 1) {
+        entry.texture0 = entry.bindings->GetVariableByName(SHADER_TYPE_PIXEL, "g_Texture0");
+    }
+    if (textures >= 2) {
+        entry.texture1 = entry.bindings->GetVariableByName(SHADER_TYPE_PIXEL, "g_Texture1");
+    }
+    return &entry;
+}
+
+} // namespace t5de

renderer/scene.hpp

@@ -0,0 +1,151 @@
+#pragma once
+// Carries out the command stream (include/t5de/protocol/commands.hpp) with Diligent, reproducing IMVU's Direct3D 9
+// look (shaders/fixed_function.hlsl): the client's textures and buffers by id, its state as it sets it, a pipeline
+// for each combination of states it draws with.
+
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <span>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "EngineFactoryD3D11.h"
+#include "RefCntAutoPtr.hpp"
+#include "t5de/protocol/commands.hpp"
+
+namespace t5de {
+
+class Scene {
+public:
+    Scene(Diligent::IRenderDevice* device, Diligent::IDeviceContext* context, Diligent::ISwapChain* swapChain);
+
+    // Carries out one frame's commands. offsetX is where the window starts within the client's 3D view; without draw,
+    // only the frame's changes are made (textures, buffers, state) and frames into the window aren't drawn (frames into
+    // render targets always are). True if the frame was drawn into the window (to present).
+    bool execute(std::span<const std::byte> commands, int offsetX, bool draw);
+
+    // Receives the pixels of frames that read their render target back (protocol::BeginFrame::readBack): rows packed,
+    // 0xAARRGGBB; empty if they couldn't be read. Valid during the call.
+    void setReadBack(std::function<void(std::span<const std::byte>)> readBack) { readBack_ = std::move(readBack); }
+
+    // Replaces the shaders' source (the built-in one by default): for trying changes while the client runs.
+    void setShaderSource(std::string source);
+
+    // When the adapter sent the last frame carried out (QueryPerformanceCounter).
+    [[nodiscard]] std::uint64_t lastSentAt() const { return lastSentAt_; }
+
+private:
+    struct Texture {
+        Diligent::RefCntAutoPtr<Diligent::ITexture> texture;
+        Diligent::RefCntAutoPtr<Diligent::ITexture> depth; // render targets only
+        std::uint32_t width = 0;
+        std::uint32_t height = 0;
+        std::uint32_t flags = 0;
+    };
+
+    struct Buffer {
+        Diligent::RefCntAutoPtr<Diligent::IBuffer> buffer;
+        protocol::BufferKind kind = protocol::BufferKind::Vertex;
+        std::uint32_t elementSize = 0;
+        std::uint32_t count = 0;
+    };
+
+    struct Pipeline {
+        Diligent::RefCntAutoPtr<Diligent::IPipelineState> state;
+        Diligent::RefCntAutoPtr<Diligent::IShaderResourceBinding> bindings;
+        Diligent::IShaderResourceVariable* texture0 = nullptr;
+        Diligent::IShaderResourceVariable* texture1 = nullptr;
+    };
+
+    struct Shaders {
+        Diligent::RefCntAutoPtr<Diligent::IShader> vertex;
+        Diligent::RefCntAutoPtr<Diligent::IShader> pixel;
+    };
+
+    // Mirrors the shader's constant buffer.
+    struct Constants {
+        float world[16];
+        float view[16];
+        float projection[16];
+        float texTransform0[8];
+        float texTransform1[8];
+        float ambient[4];
+        float lightColor[8][4];
+        float lightVector[8][4];
+        float fogColor[4];
+        float fog[4];
+        float flags[4];
+        float viewport[4];
+    };
+
+    // What a draw needs from the state, as set by the client.
+    struct State {
+        bool depthTest = true;
+        bool depthWrite = true;
+        bool blending = false;
+        std::uint32_t blendMode = 1;
+        bool culling = true;
+        bool normalInverting = false;
+        std::uint32_t texture0 = 0;
+        std::uint32_t texture1 = 0;
+    };
+
+    void createTexture(const protocol::Command& command);
+    void createRenderTarget(const protocol::CreateRenderTarget& create);
+    void beginFrame(const protocol::BeginFrame& begin);
+    void endFrame();
+    // Sets the viewport for the last projection, in what the frame draws into.
+    void setViewport();
+    // The render target's pixels, rows packed, 0xAARRGGBB; empty if it can't be read.
+    std::span<const std::byte> readTarget(const Texture& target);
+    void updateTexture(const protocol::Command& command);
+    void createBuffer(const protocol::Command& command);
+    void updateBuffer(const protocol::Command& command);
+    void setProjection(const protocol::SetProjection& projection);
+    void setState(const protocol::SetState& state);
+    void drawTriangles(const protocol::DrawTriangles& draw);
+    void drawArrays(const protocol::Command& command);
+    void drawPointSprites(const protocol::Command& command);
+
+    // Draws indexCount indices from index, with vertex streams (positions required, the others may be null).
+    void draw(Diligent::IBuffer* indices, std::uint32_t indexCount, Diligent::IBuffer* positions,
+              Diligent::IBuffer* normals, Diligent::IBuffer* texCoords, Diligent::IBuffer* colors);
+    // The pipeline for the current state, with these vertex streams and textures, for triangles or particles.
+    Pipeline* pipeline(std::uint32_t streams, std::uint32_t textures, bool sprites);
+    const Shaders& shaders(std::uint32_t streams, std::uint32_t textures, bool sprites);
+    // Picks the pipeline for the current state and sets it up for a draw: constants, textures. Null if it can't.
+    Pipeline* prepare(std::uint32_t streams, bool sprites);
+    Diligent::ITextureView* textureView(std::uint32_t id);
+
+    Diligent::RefCntAutoPtr<Diligent::IRenderDevice> device_;
+    Diligent::RefCntAutoPtr<Diligent::IDeviceContext> context_;
+    Diligent::RefCntAutoPtr<Diligent::ISwapChain> swapChain_;
+    Diligent::RefCntAutoPtr<Diligent::IBuffer> constantBuffer_;
+    Diligent::RefCntAutoPtr<Diligent::ISampler> samplers_[4]; // by wrap u (1) and wrap v (2)
+
+    std::unordered_map<std::uint32_t, Texture> textures_;
+    std::unordered_map<std::uint32_t, Buffer> buffers_;
+    std::unordered_map<std::uint32_t, Shaders> shaders_;
+    std::unordered_map<std::uint32_t, Pipeline> pipelines_;
+    std::string shaderSource_;
+
+    Constants constants_{};
+    State state_;
+    // What the current frame draws into: the window, a render target, or nothing (a frame not drawn).
+    bool onscreen_ = false; // in a frame drawn into the window
+    Texture* target_ = nullptr; // in a frame drawn into this render target
+    bool readsBack_ = false;    // the frame's render target is read back at its end
+    Diligent::ITextureView* colorView_ = nullptr;
+    Diligent::ITextureView* depthView_ = nullptr;
+    std::int32_t projectionWidth_ = 0;
+    std::int32_t projectionHeight_ = 0;
+    std::function<void(std::span<const std::byte>)> readBack_;
+    std::vector<std::byte> readPixels_;
+    bool draw_ = true;
+    std::uint64_t lastSentAt_ = 0;
+    int offsetX_ = 0;
+};
+
+} // namespace t5de

renderer/shaders/embed.hpp.in

@@ -0,0 +1,4 @@
+#pragma once
+// Generated by CMake from renderer/shaders/@T5DE_SHADER_FILE@: the shader source, compiled at run time by Diligent.
+
+inline constexpr const char* @T5DE_SHADER_NAME@ = R"hlsl(@T5DE_SHADER_SOURCE@)hlsl";

renderer/shaders/fixed_function.hlsl

@@ -0,0 +1,146 @@
+// IMVU's Direct3D 9 fixed-function look, as its renderer sets it up (docs/interface.md):
+// - per-vertex (Gouraud) lighting, with the vertex color as diffuse and ambient material (white without one): the
+//   environment's ambient light, plus each light's color times max(0, N.L); no specular or emissive light;
+// - textures: none (the lit color), one (times the lit color), or two (the second blended over the first by its
+//   alpha, then times the lit color), both on the vertex's texture coordinates with their own transforms;
+// - an alpha test passing pixels whose alpha is greater than the reference, then linear fog by view depth (checked
+//   against the client: fogging by depth buffer value instead looks nothing like it).
+//
+// Particles (vs_sprite) are Direct3D 9 point sprites there: camera-facing squares, viewport height / distance pixels
+// across (1 to 64), textured over the whole square; here each is drawn as an instance of a 4-vertex strip.
+//
+// Compiled for each combination of the vertex streams present (HAS_NORMALS, HAS_TEX_COORDS, HAS_COLORS) and the
+// number of textures (TEXTURES).
+
+cbuffer Constants
+{
+    row_major float4x4 g_World;
+    row_major float4x4 g_View;
+    row_major float4x4 g_Projection;
+    float4 g_TexTransform0[2]; // u' = dot((u, v, 1), [0].xyz), v' = dot((u, v, 1), [1].xyz)
+    float4 g_TexTransform1[2];
+    float4 g_Ambient;          // rgb
+    float4 g_LightColor[8];    // rgb, a: enabled
+    float4 g_LightVector[8];   // xyz: position, or direction toward the light; w: 1 if directional
+    float4 g_FogColor;         // rgb
+    float4 g_Fog;              // x: start, y: end, z: on
+    float4 g_Flags;            // x: lighting on, y: alpha test on, z: alpha reference (0-255)
+    float4 g_Viewport;         // xy: size in pixels
+};
+
+struct VSInput
+{
+    float3 Position : ATTRIB0;
+#if HAS_NORMALS
+    float3 Normal : ATTRIB1;
+#endif
+#if HAS_TEX_COORDS
+    float2 TexCoord : ATTRIB2;
+#endif
+#if HAS_COLORS
+    float4 Color : ATTRIB3; // bytes B, G, R, A
+#endif
+};
+
+struct PSInput
+{
+    float4 Position : SV_POSITION;
+    float4 Color : COLOR0;
+    float2 TexCoord0 : TEXCOORD0;
+    float2 TexCoord1 : TEXCOORD1;
+    float Depth : TEXCOORD2;
+};
+
+void vs_main(in VSInput input, out PSInput output)
+{
+    float4 world = mul(float4(input.Position, 1.0), g_World);
+    float4 view = mul(world, g_View);
+    output.Position = mul(view, g_Projection);
+    output.Depth = abs(view.z);
+
+    float4 material = float4(1.0, 1.0, 1.0, 1.0);
+#if HAS_COLORS
+    material = input.Color.zyxw;
+#endif
+    float4 color = material;
+    if (g_Flags.x > 0.5)
+    {
+        float3 normal = float3(0.0, 0.0, 0.0);
+#if HAS_NORMALS
+        normal = normalize(mul(input.Normal, (float3x3)g_World));
+#endif
+        float3 lit = g_Ambient.rgb * material.rgb;
+        for (int i = 0; i < 8; ++i)
+        {
+            if (g_LightColor[i].a > 0.5)
+            {
+                float3 toLight = g_LightVector[i].w > 0.5 ? g_LightVector[i].xyz : g_LightVector[i].xyz - world.xyz;
+                lit += g_LightColor[i].rgb * material.rgb * max(0.0, dot(normal, normalize(toLight)));
+            }
+        }
+        color = float4(saturate(lit), material.a);
+    }
+    output.Color = color;
+
+    float3 uv = float3(0.0, 0.0, 1.0);
+#if HAS_TEX_COORDS
+    uv.xy = input.TexCoord;
+#endif
+    output.TexCoord0 = float2(dot(uv, g_TexTransform0[0].xyz), dot(uv, g_TexTransform0[1].xyz));
+    output.TexCoord1 = float2(dot(uv, g_TexTransform1[0].xyz), dot(uv, g_TexTransform1[1].xyz));
+}
+
+struct SpriteInput
+{
+    float3 Position : ATTRIB0;
+    float4 Color : ATTRIB3; // bytes B, G, R, A
+    uint Corner : SV_VertexID;
+};
+
+void vs_sprite(in SpriteInput input, out PSInput output)
+{
+    float4 view = mul(mul(float4(input.Position, 1.0), g_World), g_View);
+    float4 clip = mul(view, g_Projection);
+    float size = clamp(g_Viewport.y / max(length(view.xyz), 1e-4), 1.0, 2048.0);
+    float2 corner = float2((input.Corner & 1) != 0 ? 1.0 : -1.0, (input.Corner & 2) != 0 ? -1.0 : 1.0);
+    clip.xy += corner * size / g_Viewport.xy * clip.w; // half the size each way, in clip space
+    output.Position = clip;
+    output.Depth = abs(view.z);
+
+    // No normals: lit by the ambient light alone.
+    float4 material = input.Color.zyxw;
+    output.Color = g_Flags.x > 0.5 ? float4(saturate(g_Ambient.rgb * material.rgb), material.a) : material;
+    output.TexCoord0 = float2(corner.x * 0.5 + 0.5, 0.5 - corner.y * 0.5);
+    output.TexCoord1 = output.TexCoord0;
+}
+
+#if TEXTURES >= 1
+Texture2D g_Texture0;
+SamplerState g_Texture0_sampler;
+#endif
+#if TEXTURES >= 2
+Texture2D g_Texture1;
+SamplerState g_Texture1_sampler;
+#endif
+
+float4 ps_main(in PSInput input) : SV_Target
+{
+    float4 color = input.Color;
+#if TEXTURES == 1
+    color *= g_Texture0.Sample(g_Texture0_sampler, input.TexCoord0);
+#elif TEXTURES == 2
+    float4 first = g_Texture0.Sample(g_Texture0_sampler, input.TexCoord0);
+    float4 second = g_Texture1.Sample(g_Texture1_sampler, input.TexCoord1);
+    color *= lerp(first, second, second.a);
+#endif
+    if (g_Flags.y > 0.5 && !(color.a * 255.0 > g_Flags.z))
+    {
+        discard;
+    }
+    if (g_Fog.z > 0.5)
+    {
+        float visible = saturate((g_Fog.y - input.Depth) / max(g_Fog.y - g_Fog.x, 1e-6));
+        color.rgb = lerp(g_FogColor.rgb, color.rgb, visible);
+    }
+    return color;
+}

src/passthrough_engine.cpp

@@ -1,290 +0,0 @@
-#include "passthrough_engine.hpp"
-
-#include <string>
-
-#include "log.hpp"
-
-namespace t5de {
-
-namespace {
-
-constexpr std::array<const char*, PassthroughEngine::slots> names = {
-    "~PiRenderEngine",
-    "resizeFrameBuffer",
-    "enable2dFrameBuffer",
-    "clear",
-    "setProjection",
-    "setModelSpace",
-    "setViewSpace",
-    "setTextures",
-    "setDepthTestingOn",
-    "setDepthWritingOn",
-    "setBlendMode",
-    "setAlphaTestingOn",
-    "setAlphaTestValue",
-    "setBlendingOn",
-    "setBackFaceCullingOn",
-    "setNormalInvertingOn",
-    "setLightingOn",
-    "setLightProperties",
-    "setFogOn",
-    "setFogAttributes",
-    "setTextureTransformMatrixIdentity",
-    "setTextureTransformMatrix",
-    "setEnvironmentAmbient",
-    "newRenderTexture",
-    "newIndexBuffer",
-    "newStaticVertexBuffer",
-    "newDynamicVertexBuffer",
-    "newPixmapRenderTarget",
-    "newTextureRenderTarget",
-    "beginRendering",
-    "endRendering",
-    "drawTriangles",
-    "drawLine",
-    "drawPointSprites",
-    "drawTrianglesFromMemory",
-};
-
-// Frames whose calls are logged: the first few, then one a minute or so at 30 FPS.
-bool logged(std::uint64_t frame) { return frame < 5 || frame % 1800 == 0; }
-
-} // namespace
-
-PassthroughEngine::PassthroughEngine(imvu::SharedPtr<imvu::PiRenderEngine> inner) : inner_(std::move(inner))
-{
-    log::info("passthrough: wrapping the engine at {}", static_cast<void*>(inner_.get()));
-}
-
-PassthroughEngine::~PassthroughEngine() { log::info("passthrough: destroyed after {} frames", frames_); }
-
-void PassthroughEngine::count(std::size_t slot) { ++calls_[slot]; }
-
-void PassthroughEngine::resizeFrameBuffer(imvu::Vec2i size)
-{
-    log::info("resizeFrameBuffer({}, {})", size.x, size.y);
-    count(1);
-    inner_->resizeFrameBuffer(size);
-}
-
-void PassthroughEngine::enable2dFrameBuffer()
-{
-    count(2);
-    inner_->enable2dFrameBuffer();
-}
-
-void PassthroughEngine::clear(std::uint32_t flags, std::uint32_t color)
-{
-    count(3);
-    inner_->clear(flags, color);
-}
-
-void PassthroughEngine::setProjection(imvu::Vec2i viewport, const imvu::Mat4f& projection)
-{
-    count(4);
-    inner_->setProjection(viewport, projection);
-}
-
-void PassthroughEngine::setModelSpace(const imvu::Transform& model)
-{
-    count(5);
-    inner_->setModelSpace(model);
-}
-
-void PassthroughEngine::setViewSpace(const imvu::Transform& view)
-{
-    count(6);
-    inner_->setViewSpace(view);
-}
-
-void PassthroughEngine::setTextures(imvu::PiRenderTexture* texture0, imvu::PiRenderTexture* texture1)
-{
-    count(7);
-    inner_->setTextures(texture0, texture1);
-}
-
-void PassthroughEngine::setDepthTestingOn(bool on)
-{
-    count(8);
-    inner_->setDepthTestingOn(on);
-}
-
-void PassthroughEngine::setDepthWritingOn(bool on)
-{
-    count(9);
-    inner_->setDepthWritingOn(on);
-}
-
-void PassthroughEngine::setBlendMode(imvu::RenderBlendMode mode)
-{
-    count(10);
-    inner_->setBlendMode(mode);
-}
-
-void PassthroughEngine::setAlphaTestingOn(bool on)
-{
-    count(11);
-    inner_->setAlphaTestingOn(on);
-}
-
-void PassthroughEngine::setAlphaTestValue(float value)
-{
-    count(12);
-    inner_->setAlphaTestValue(value);
-}
-
-void PassthroughEngine::setBlendingOn(bool on)
-{
-    count(13);
-    inner_->setBlendingOn(on);
-}
-
-void PassthroughEngine::setBackFaceCullingOn(bool on)
-{
-    count(14);
-    inner_->setBackFaceCullingOn(on);
-}
-
-void PassthroughEngine::setNormalInvertingOn(bool on)
-{
-    count(15);
-    inner_->setNormalInvertingOn(on);
-}
-
-void PassthroughEngine::setLightingOn(bool on)
-{
-    count(16);
-    inner_->setLightingOn(on);
-}
-
-void PassthroughEngine::setLightProperties(std::uint32_t index, const imvu::LightProperties& light)
-{
-    count(17);
-    inner_->setLightProperties(index, light);
-}
-
-void PassthroughEngine::setFogOn(bool on)
-{
-    count(18);
-    inner_->setFogOn(on);
-}
-
-void PassthroughEngine::setFogAttributes(float start, float end, std::uint32_t color)
-{
-    count(19);
-    inner_->setFogAttributes(start, end, color);
-}
-
-void PassthroughEngine::setTextureTransformMatrixIdentity(std::uint32_t stage)
-{
-    count(20);
-    inner_->setTextureTransformMatrixIdentity(stage);
-}
-
-void PassthroughEngine::setTextureTransformMatrix(std::uint32_t stage, const imvu::TextureTransform& transform)
-{
-    count(21);
-    inner_->setTextureTransformMatrix(stage, transform);
-}
-
-void PassthroughEngine::setEnvironmentAmbient(std::uint32_t color)
-{
-    count(22);
-    inner_->setEnvironmentAmbient(color);
-}
-
-imvu::PiRenderTexture* PassthroughEngine::newRenderTexture(imvu::Pixmap* pixmap, std::uint32_t flags)
-{
-    count(23);
-    return inner_->newRenderTexture(pixmap, flags);
-}
-
-imvu::PiInternalIndexBuffer* PassthroughEngine::newIndexBuffer(std::uint32_t indexCount, const std::uint16_t* indices)
-{
-    count(24);
-    return inner_->newIndexBuffer(indexCount, indices);
-}
-
-imvu::PiInternalVertexBuffer* PassthroughEngine::newStaticVertexBuffer(const void* data, std::uint32_t a,
-                                                                       std::uint32_t b, std::uint32_t c)
-{
-    count(25);
-    return inner_->newStaticVertexBuffer(data, a, b, c);
-}
-
-imvu::PiInternalVertexBuffer* PassthroughEngine::newDynamicVertexBuffer(std::uint32_t a, std::uint32_t b)
-{
-    count(26);
-    return inner_->newDynamicVertexBuffer(a, b);
-}
-
-imvu::SharedPtr<imvu::PiPixmapRenderTarget> PassthroughEngine::newPixmapRenderTarget(imvu::Vec2i size)
-{
-    log::info("newPixmapRenderTarget({}, {})", size.x, size.y);
-    count(27);
-    return inner_->newPixmapRenderTarget(size);
-}
-
-imvu::SharedPtr<imvu::PiTextureRenderTarget> PassthroughEngine::newTextureRenderTarget(imvu::Vec2i size)
-{
-    log::info("newTextureRenderTarget({}, {})", size.x, size.y);
-    count(28);
-    return inner_->newTextureRenderTarget(size);
-}
-
-void PassthroughEngine::beginRendering(imvu::PiRenderTarget* target)
-{
-    count(29);
-    inner_->beginRendering(target);
-}
-
-void PassthroughEngine::endRendering()
-{
-    count(30);
-    inner_->endRendering();
-    if (logged(frames_)) {
-        std::string line = std::format("frame {}:", frames_);
-        for (std::size_t slot = 1; slot < slots; ++slot) {
-            if (calls_[slot] != 0) {
-                line += std::format(" {} x{},", names[slot], calls_[slot]);
-            }
-        }
-        line.pop_back();
-        log::write(line);
-    }
-    calls_ = {};
-    ++frames_;
-}
-
-void PassthroughEngine::drawTriangles(imvu::PiInternalIndexBuffer* indices, imvu::PiInternalVertexBuffer* positions,
-                                      imvu::PiInternalVertexBuffer* normals, imvu::PiInternalVertexBuffer* texCoords0,
-                                      imvu::PiInternalVertexBuffer* texCoords1)
-{
-    count(31);
-    inner_->drawTriangles(indices, positions, normals, texCoords0, texCoords1);
-}
-
-void PassthroughEngine::drawLine(imvu::Vec3f from, imvu::Vec3f to, std::uint32_t color)
-{
-    count(32);
-    inner_->drawLine(from, to, color);
-}
-
-void PassthroughEngine::drawPointSprites(const imvu::PointSpriteVector& sprites)
-{
-    count(33);
-    inner_->drawPointSprites(sprites);
-}
-
-void PassthroughEngine::drawTrianglesFromMemory(std::uint32_t vertexCount, std::uint32_t indexCount,
-                                                const std::uint16_t* indices,
-                                                const imvu::VertexAttributeArray<imvu::Vec3f>& positions,
-                                                const imvu::VertexAttributeArray<imvu::Vec3f>& normals,
-                                                const imvu::VertexAttributeArray<imvu::Vec2f>& texCoords,
-                                                const imvu::VertexAttributeArray<std::uint32_t>& colors)
-{
-    count(34);
-    inner_->drawTrianglesFromMemory(vertexCount, indexCount, indices, positions, normals, texCoords, colors);
-}
-
-} // namespace t5de

src/passthrough_engine.hpp

@@ -1,70 +0,0 @@
-#pragma once
-// A renderer that forwards every call to another one (IMVU's Direct3D engine) and logs what a frame is made of: proof
-// that our declaration of the interface matches IMVU's, and a way to see how the client draws.
-
-#include <array>
-#include <cstdint>
-
-#include "t5de/imvu/render_engine.hpp"
-
-namespace t5de {
-
-class PassthroughEngine final : public imvu::PiRenderEngine {
-public:
-    explicit PassthroughEngine(imvu::SharedPtr<imvu::PiRenderEngine> inner);
-    ~PassthroughEngine() override;
-
-    void resizeFrameBuffer(imvu::Vec2i size) override;
-    void enable2dFrameBuffer() override;
-    void clear(std::uint32_t flags, std::uint32_t color) override;
-    void setProjection(imvu::Vec2i viewport, const imvu::Mat4f& projection) override;
-    void setModelSpace(const imvu::Transform& model) override;
-    void setViewSpace(const imvu::Transform& view) override;
-    void setTextures(imvu::PiRenderTexture* texture0, imvu::PiRenderTexture* texture1) override;
-    void setDepthTestingOn(bool on) override;
-    void setDepthWritingOn(bool on) override;
-    void setBlendMode(imvu::RenderBlendMode mode) override;
-    void setAlphaTestingOn(bool on) override;
-    void setAlphaTestValue(float value) override;
-    void setBlendingOn(bool on) override;
-    void setBackFaceCullingOn(bool on) override;
-    void setNormalInvertingOn(bool on) override;
-    void setLightingOn(bool on) override;
-    void setLightProperties(std::uint32_t index, const imvu::LightProperties& light) override;
-    void setFogOn(bool on) override;
-    void setFogAttributes(float start, float end, std::uint32_t color) override;
-    void setTextureTransformMatrixIdentity(std::uint32_t stage) override;
-    void setTextureTransformMatrix(std::uint32_t stage, const imvu::TextureTransform& transform) override;
-    void setEnvironmentAmbient(std::uint32_t color) override;
-    imvu::PiRenderTexture* newRenderTexture(imvu::Pixmap* pixmap, std::uint32_t flags) override;
-    imvu::PiInternalIndexBuffer* newIndexBuffer(std::uint32_t count, const std::uint16_t* indices) override;
-    imvu::PiInternalVertexBuffer* newStaticVertexBuffer(const void* data, std::uint32_t a, std::uint32_t b,
-                                                        std::uint32_t c) override;
-    imvu::PiInternalVertexBuffer* newDynamicVertexBuffer(std::uint32_t a, std::uint32_t b) override;
-    imvu::SharedPtr<imvu::PiPixmapRenderTarget> newPixmapRenderTarget(imvu::Vec2i size) override;
-    imvu::SharedPtr<imvu::PiTextureRenderTarget> newTextureRenderTarget(imvu::Vec2i size) override;
-    void beginRendering(imvu::PiRenderTarget* target) override;
-    void endRendering() override;
-    void drawTriangles(imvu::PiInternalIndexBuffer* indices, imvu::PiInternalVertexBuffer* positions,
-                       imvu::PiInternalVertexBuffer* normals, imvu::PiInternalVertexBuffer* texCoords0,
-                       imvu::PiInternalVertexBuffer* texCoords1) override;
-    void drawLine(imvu::Vec3f from, imvu::Vec3f to, std::uint32_t color) override;
-    void drawPointSprites(const imvu::PointSpriteVector& sprites) override;
-    void drawTrianglesFromMemory(std::uint32_t vertexCount, std::uint32_t indexCount, const std::uint16_t* indices,
-                                 const imvu::VertexAttributeArray<imvu::Vec3f>& positions,
-                                 const imvu::VertexAttributeArray<imvu::Vec3f>& normals,
-                                 const imvu::VertexAttributeArray<imvu::Vec2f>& texCoords,
-                                 const imvu::VertexAttributeArray<std::uint32_t>& colors) override;
-
-    // The interface's methods, by vtable slot (slot 0, the destructor, isn't counted).
-    static constexpr std::size_t slots = 35;
-
-private:
-    void count(std::size_t slot);
-
-    imvu::SharedPtr<imvu::PiRenderEngine> inner_;
-    std::array<std::uint32_t, slots> calls_{};
-    std::uint64_t frames_ = 0;
-};
-
-} // namespace t5de

tests/CMakeLists.txt

@@ -1,3 +1,7 @@
 add_executable(shared_ptr_test shared_ptr_test.cpp)
 target_link_libraries(shared_ptr_test PRIVATE t5de::imvu t5de::options)
 add_test(NAME shared_ptr COMMAND shared_ptr_test)
+
+add_executable(protocol_test protocol_test.cpp)
+target_link_libraries(protocol_test PRIVATE t5de::protocol t5de::options)
+add_test(NAME protocol COMMAND protocol_test)

tests/protocol_test.cpp

@@ -0,0 +1,61 @@
+// The command stream: what the adapter writes, the renderer process reads back the same.
+
+#include <cstdio>
+#include <cstring>
+
+#include "t5de/protocol/commands.hpp"
+
+using namespace t5de::protocol;
+
+namespace {
+
+int failures = 0;
+
+void check(bool ok, const char* what)
+{
+    if (!ok) {
+        std::printf("FAIL: %s\n", what);
+        ++failures;
+    }
+}
+
+} // namespace
+
+int main()
+{
+    Writer writer;
+    writer.add(Op::Clear, Clear{3, 0xff131313});
+    const unsigned char pixels[] = {1, 2, 3, 4, 5, 6, 7, 8};
+    std::memcpy(writer.add(Op::CreateTexture, CreateTexture{7, 2, 1, 6}, sizeof(pixels)), pixels, sizeof(pixels));
+    std::byte* odd = writer.add(Op::UpdateBuffer, UpdateBuffer{9, 1, 3}, 3); // padded to 4
+    std::memset(odd, 0xab, 3);
+    writer.add(Op::EndFrame, EndFrame{});
+    check(writer.size() % 4 == 0, "commands stay 4-byte aligned");
+
+    Reader reader(writer.bytes());
+    auto clear = reader.next();
+    check(clear && clear->op() == Op::Clear && clear->body<Clear>()->color == 0xff131313, "clear");
+    auto texture = reader.next();
+    check(texture && texture->op() == Op::CreateTexture && texture->body<CreateTexture>()->id == 7, "texture");
+    check(texture && texture->payload<CreateTexture>().size() == sizeof(pixels)
+              && std::memcmp(texture->payload<CreateTexture>().data(), pixels, sizeof(pixels)) == 0,
+          "texture pixels");
+    auto update = reader.next();
+    check(update && update->payload<UpdateBuffer>().size() == 4, "payload padded");
+    auto end = reader.next();
+    check(end && end->op() == Op::EndFrame, "end of frame");
+    check(!reader.next(), "nothing after");
+
+    // A truncated stream (a chunk cut short) yields only whole commands.
+    Reader truncated(writer.bytes().first(writer.size() - 2));
+    int count = 0;
+    while (truncated.next()) {
+        ++count;
+    }
+    check(count == 3, "truncated: whole commands only");
+
+    if (failures == 0) {
+        std::printf("ok\n");
+    }
+    return failures == 0 ? 0 : 1;
+}