Declare the renderer interface's data types

Transforms, matrices, colors, lights, blend modes, fog, texture transforms, vertex arrays and the engine's buffer and texture objects, worked out from IMVU's Direct3D engine. The pass-through logs the first calls' arguments read through them, to check them in the client.

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

docs/interface.md

@@ -59,9 +59,17 @@ 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.
+- Still unknown: point sprites (`drawPointSprites`, particles), render targets, `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.