Dan Lee

dlee

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Merging two BSDFs brings Noise April 2, 2019, 10:50 p.m.

jerry7
Thank you for reply. I want to know why PBR Reflecton and PBR Refraction is ok? What different between them and reflected/refracted light vop? Are they both BSDFs?

Reflected/refracted Light VOPs can output BSDF (“f” output, either cone or specular depending on parameters). PBR Reflection/Refraction VOPs are more modern and give you a lot more options. They also have constant albedo unaffected by builtin fresnel (for better or worse - better, in this case), so when you add both together, they each get 50/50 chance of being sampled by the light.

Opacity independent shading April 1, 2019, 3:13 p.m.

As long as you're using “raytrace” render engine with stochastic transparency disabled, it should be doable. (in your material, feed 1 into “Of” input of Compute Lighting VOP, and 0 into “Of” of surface output.

Merging two BSDFs brings Noise April 1, 2019, 3:06 p.m.

It's not a bug, it's an unfortunate consequences of having 2 bsdfs stacked together. Direct lighting chooses which bsdf to evaluate based on their albedo. The reflection contribution (“kr”) from fresnel is only about 2~3% of the combined contribution (in the circled region), so the vast majority of the lighting samples are reserved for refraction and not enough is left over for reflection.
The recommended solution for such case is to increase shading quality on the light, but there are other workarounds. e.g. add PBR Reflecton and PBR Refraction vops together (with fresnel blend enabled on the bsdfs).