perf(particlesys): Improve particle rendering performance using texture atlas

[stephanmeesters]

• Implement texture atlas and unit tests.
• Adjust sorting renderer to draw multiple triangles in the same call if render state matches (same texture, same blending mode, etc).
• Adjust ParticleSys to use the new texture atlas with a shared blending mode

Adds 77% performance to a busy scene.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 6a4a705a-5704-45c4-82a3-d47d215747ba

📥 Commits

Reviewing files that changed from the base of the PR and between e572d87 and d86f8b4.

📒 Files selected for processing: 10

• Core/GameEngineDevice/Include/W3DDevice/GameClient/W3DParticleSys.h
• Core/GameEngineDevice/Source/W3DDevice/GameClient/W3DParticleSys.cpp
• Core/Libraries/Source/WWVegas/WW3D2/CMakeLists.txt
• Core/Libraries/Source/WWVegas/WW3D2/pointgr.cpp
• Core/Libraries/Source/WWVegas/WW3D2/pointgr.h
• Core/Libraries/Source/WWVegas/WW3D2/sortingrenderer.cpp
• Core/Libraries/Source/WWVegas/WW3D2/textureatlas.cpp
• Core/Libraries/Source/WWVegas/WW3D2/textureatlas.h
• Tests/Google/Core/CMakeLists.txt
• Tests/Google/Core/Libraries/WW3D2/TextureAtlasTest.cpp

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Walkthrough

The particle renderer now uses texture atlases for eligible particle systems and remaps particle UVs to atlas regions. The sorting renderer also groups consecutive triangles with compatible render states into shared draws.

Changes

Particle Texture Atlasing

Layer / File(s)	Summary
Texture atlas storage and pixel operations Core/Libraries/Source/WWVegas/WW3D2/textureatlas.h, Core/Libraries/Source/WWVegas/WW3D2/textureatlas.cpp, Core/Libraries/Source/WWVegas/WW3D2/CMakeLists.txt, Tests/Google/Core/Libraries/WW3D2/TextureAtlasTest.cpp, Tests/Google/Core/CMakeLists.txt	TextureAtlasClass adds paged texture storage, lookup and insertion, mip-level copying, premultiplication, and padding. Tests cover coordinate wrapping, premultiplication, and padding.
Particle batching with atlas UVs Core/GameEngineDevice/Include/W3DDevice/GameClient/W3DParticleSys.h, Core/GameEngineDevice/Source/W3DDevice/GameClient/W3DParticleSys.cpp, Core/Libraries/Source/WWVegas/WW3D2/pointgr.h, Core/Libraries/Source/WWVegas/WW3D2/pointgr.cpp	W3DParticleSystemManager resolves atlas textures and shaders for eligible systems, stores per-particle UV rectangles, and passes them to PointGroupClass. PointGroupClass remaps generated UVs into those rectangles.

Sorting Renderer Batching

Layer / File(s)	Summary
Group draws by compatible render state Core/Libraries/Source/WWVegas/WW3D2/sortingrenderer.cpp	Same_Render_State checks shader bits, textures, matrices, and material conditions. Compatible consecutive nodes within a chunk share a draw using the first node’s render state.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Other

Sequence Diagram(s)

sequenceDiagram
  participant W3DParticleSystemManager
  participant TextureAtlasClass
  participant PointGroupClass
  W3DParticleSystemManager->>TextureAtlasClass: Find_Or_Insert particle texture and receive atlas UV rectangle
  W3DParticleSystemManager->>PointGroupClass: Set_Texture_UV_Rects for particle rendering
  PointGroupClass->>PointGroupClass: Remap generated UVs during Render

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Suggested reviewers: mauller, lfeenanea, xezon

Merge Risk: ⚪ Minimal · up to d86f8

The change batches particle rendering through a texture atlas and groups compatible draws. No concrete merge-blocking defect was established. Confirm that the new texture atlas test builds in CI.

Pre-merge checks: 4

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly and concisely describes the main change: improving particle rendering performance with a texture atlas.
Description check		The description directly covers the texture atlas, batching changes, ParticleSys integration, tests, and reported performance improvement.

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