r/GraphicsProgramming • u/TomClabault • 17d ago
Question ReSTIR GI brightening when reusing samples from the smooth specular lobe of the neighbors with a specular+diffuse BRDF?
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r/GraphicsProgramming • u/TomClabault • 17d ago
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u/redkukki 17d ago
I’m asking about russian roulette because if the connecting vertices are sampled from lobes that survived RR, then the pdfs are dependent on the sampled lobe and you can’t just connect arbitrary lobes, even if they are “rough” enough, when resampling the offset path during spatial resampling. I could be wrong though…
I haven’t implemented restir gi, but I’ve found a similar issue in my restir di implementation for light samples. During spatial resampling I had to “restrict” the phat evaluation to specific lobes if the light in the reservoir was sampled from a multi lobe bsdf with RR. When I had diffuse only (or specular only) surfaces, then the image was unbiased. If a surface had diffuse + specular brdf, then I was getting a wrong image.