WebGPURenderer: Implement GGX VNDF importance sampling for PMREM #32134
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mrdoob
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📦 Bundle sizeFull ESM build, minified and gzipped.
🌳 Bundle size after tree-shakingMinimal build including a renderer, camera, empty scene, and dependencies.
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mrdoob
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@sunag What do you think? |
mrdoob
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Port the GGX VNDF (Visible Normal Distribution Function) importance sampling implementation from WebGLRenderer's PMREM to WebGPURenderer's TSL-based PMREM generator. This implementation provides more accurate environment map prefiltering by using Monte Carlo integration with VNDF importance sampling to represent the GGX BRDF for physically-based rendering. Changes to PMREMUtils.js: - Added GGX VNDF sampling helper functions: - radicalInverse_VdC: Van der Corput radical inverse - hammersley: Hammersley sequence for quasi-Monte Carlo sampling - importanceSampleGGX_VNDF: GGX VNDF importance sampling (Heitz 2018) - ggxConvolution: Main convolution function using VNDF sampling - Optimized shader code by removing unnecessary .toVar() calls Changes to PMREMGenerator.js: - Added GGX_SAMPLES constant (1024 samples, optimized for performance) - Removed _axisDirections (no longer needed with GGX filtering) - Added _ggxMaterial property - Replaced blur-based _applyPMREM with GGX filtering - Added _applyGGXFilter method for incremental roughness filtering - Added _getGGXShader function to create GGX material - Updated documentation to reflect GGX VNDF usage Technical notes: - Uses texture() instead of texture(null) for EmptyTexture default - Helper functions don't use setLayout (TSL pattern for nested Fn) - Implements incremental roughness filtering to avoid over-blurring - Applies blur strength mapping (0.05 + roughness * 0.95) for quality - Performs two-pass rendering: pingPong target then back to cubeUV - Reduced sample count to 1024 (vs WebGL's 2048) for better performance
mrdoob
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Oh, it may be unstable now. Trying to make it perform faster so the e2e doesn't timeout. |
The implementation seems perfect. 👏 |
It seems that the material is being compiled multiple times even with the ggx material cache 🤔 |
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Feel free to continue the PR. It's sleep time for me 🤓 |
Performance optimization: removed .toVar() from the s variable in importanceSampleGGX_VNDF as it is never reassigned and only used for reading on the next line. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <[email protected]>
…0.0.1:27907/git/mrdoob/three.js into claude/session-011CUZfd82vQUmMrBBmDS1CQ
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I'm still investigating, but the performance issue isn't related to the code but to the caching system associated with |
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Seems like 2048 is too much for I'll set it back to 1024 and next month I'll try to profile the renderer and see if I can find any performance improvements. |
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Related issue: #32114
Description
Port the GGX VNDF (Visible Normal Distribution Function) importance sampling implementation from WebGLRenderer's PMREM to WebGPURenderer's TSL-based PMREM generator.
This implementation provides more accurate environment map prefiltering by using Monte Carlo integration with VNDF importance sampling to represent the GGX BRDF for physically-based rendering.
Changes to PMREMUtils.js:
Changes to PMREMGenerator.js:
Technical notes: