Cycles random walk subsurface scattering produces anisotropic artifacts if subsurface radius is small compared to geometry's distance from origin #78454

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Tom Benedett · 2020-06-30T08:33:58+02:00

Tom Benedett commented

2020-06-30 08:33:58 +02:00

System Information
Operating system: Windows 10
Graphics card: GTX 1080 ti

Blender Version
Broken: 2.90.0 b21ba5e5795 (Jun. 28th, 2020 Windows buildbot) and all others tested back to 2.79.6 66ad9ef2ce (Sep. 14th 2018 Windows buildbot)
Working: none known

Short description of error
On a Cycles material with random walk subsurface scattering, and subsurface radius that is small relative to the geometry's distance to the origin, and the faces that have normal components significantly parallel or antiparallel to the direction to the origin see significant darkening relative to the shader's isotropic behavior near the origin.

Exact steps for others to reproduce the error
Put a UV sphere at location (1000,0,0) and put a Cycles material on it: principled BSDF with subsurface component 1.0 and subsurface radius scaled down by 100 from default to (0.01,0.002,0.001) and observe that all the faces except a longitudinal ring in a plane normal to the vector to the origin become much darker brown than they would be if the sphere were at the origin.

(Shown in attached .blend file)Cycles Random Walk Subsurface Scattering Artifact - 2.90.0 b21ba5e5795 Windows 10.blend

**System Information** Operating system: Windows 10 Graphics card: GTX 1080 ti **Blender Version** Broken: 2.90.0 b21ba5e5795 (Jun. 28th, 2020 Windows buildbot) and all others tested back to 2.79.6 66ad9ef2ce3 (Sep. 14th 2018 Windows buildbot) Working: none known **Short description of error** On a Cycles material with random walk subsurface scattering, and subsurface radius that is small relative to the geometry's distance to the origin, and the faces that have normal components significantly parallel or antiparallel to the direction to the origin see significant darkening relative to the shader's isotropic behavior near the origin. **Exact steps for others to reproduce the error** Put a UV sphere at location (1000,0,0) and put a Cycles material on it: principled BSDF with subsurface component 1.0 and subsurface radius scaled down by 100 from default to (0.01,0.002,0.001) and observe that all the faces except a longitudinal ring in a plane normal to the vector to the origin become much darker brown than they would be if the sphere were at the origin. (Shown in attached .blend file)[Cycles Random Walk Subsurface Scattering Artifact - 2.90.0 b21ba5e5795 Windows 10.blend](https://archive.blender.org/developer/F8654827/Cycles_Random_Walk_Subsurface_Scattering_Artifact_-_2.90.0_b21ba5e5795_Windows_10.blend) ![Cycles Random Walk Subsurface Scattering Artifact - 2.90.0 b21ba5e5795 Windows 10 example.png](https://archive.blender.org/developer/F8654828/Cycles_Random_Walk_Subsurface_Scattering_Artifact_-_2.90.0_b21ba5e5795_Windows_10_example.png)

Tom Benedett commented

2020-06-30 08:33:58 +02:00

Added subscriber: @moak

Evan Wilson commented

2020-06-30 10:59:46 +02:00

Closed as duplicate of #64620

Evan Wilson closed this issue

2020-06-30 10:59:46 +02:00

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Cycles random walk subsurface scattering produces anisotropic artifacts if subsurface radius is small compared to geometry's distance from origin #78454