Add the renderer process

The renderer becomes two programs: the adapter (t5deRenderEngine.dll, 32-bit, in IMVU's process) and a 64-bit renderer process (t5de-renderer.exe) drawing with Diligent Engine, fetched with FetchContent and pinned. For now a spike: the adapter starts the renderer process for each engine and signals each frame through a shared memory channel, and the renderer process draws a box into a child window in the client's 3D view.

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

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`.