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| author | Brecht Van Lommel <brecht@blender.org> | 2021-10-08 20:44:56 +0300 |
|---|---|---|
| committer | Brecht Van Lommel <brecht@blender.org> | 2021-10-11 19:22:54 +0300 |
| commit | a94343a8afcac5d6db09c8461e67ad1ba5a85d35 (patch) | |
| tree | f56b8e6a956ca87f25b01f94b6f6421636448402 /intern/cycles/blender | |
| parent | 73a05ff9e83a31be34d32a92cd5fb4d17994e342 (diff) | |
Cycles: improve SSS Fresnel and retro-reflection in Principled BSDF
For details see the "Extending the Disney BRDF to a BSDF with Integrated
Subsurface Scattering" paper.
We split the diffuse BSDF into a lambertian and retro-reflection component.
The retro-reflection component is always handled as a BSDF, while the
lambertian component can be replaced by a BSSRDF.
For the BSSRDF case, we compute Fresnel separately at the entry and exit
points, which may have different normals. As the scattering radius decreases
this converges to the BSDF case.
A downside is that this increases noise for subsurface scattering in the
Principled BSDF, due to some samples going to the retro-reflection component.
However the previous logic (also in 2.93) was simple wrong, using a
non-sensical view direction vector at the exit point. We use an importance
sampling weight estimate for the retro-reflection to try to better balance
samples between the BSDF and BSSRDF.
Differential Revision: https://developer.blender.org/D12801
Diffstat (limited to 'intern/cycles/blender')
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