Draw particles, match the client's fog, and measure frame delay

Particles (point sprites) are drawn as instanced camera-facing squares sized like Direct3D 9's. Fog is by depth buffer value, as Direct3D 9 does with IMVU's projections. At most one frame is queued for display, frames carry the adapter's timestamp so the renderer process logs the delay to presenting, and the log's lines from several processes no longer mix.

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

include/t5de/imvu/types.hpp

@@ -90,8 +90,21 @@ static_assert(sizeof(VertexAttributeArray<Vec3f>) == 12);
 // (width, height, pitch, rowBytes, pixels, ...).
 class Pixmap;
 
-// Unknown so far: used only by drawPointSprites (particles), as a Visual C++ 2010 std::vector<PointSprite>.
-struct PointSpriteVector;
+// 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;