Maniphest T83006

Eevees Principled BSDF handles external SSS radius values incorrectly
Closed, Archived
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Assigned To
None
Authored By
Jon Henry M. Faltis 9077149 (295032)
Nov 25 2020, 5:24 PM
Tags
  • BF Blender
Subscribers
Clément Foucault (fclem)
Evan Wilson (EAW)
Jon Henry M. Faltis 9077149 (295032)
michael campbell (3di)

Description

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.66

Blender Version
Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-11-24 16:32, hash: rBe922dd7d8a30
Worked: -

Short description of error
Using combine RGB/XYZ or Nodegroup linked to Eevee's principled BSDF SSS radius produces incorrect results.
The radius of SSS changes slightly, but it still retains the overall color defined in the default value of the principled BSDFs SSS radius (provided the external values aren't extreme).
Cycles seems to handle it correctly.

Edit: Apparently It's a know limitation of Eevee and shader nodes.

Exact steps for others to reproduce the error
Open attatched blend file, switch to rendered mode, compare Cycles and Eevee results.

SSGI_SSS_Bug.blend21 MBDownload

Related Objects

Event Timeline

Jon Henry M. Faltis 9077149 (295032) created this task.Nov 25 2020, 5:24 PM
Jon Henry M. Faltis 9077149 (295032) updated the task description.Nov 25 2020, 5:43 PM
Evan Wilson (EAW) closed this task as Archived.Nov 25 2020, 9:11 PM
Evan Wilson (EAW) added a subscriber: Evan Wilson (EAW).

Thank you for the report. As you noticed, this is a documented limitation in the manual. As such, I’ll be closing this report.

(This is outside the scope of the bug tracker, and I have no idea if it will work, but have you tried using a driver to pass the values to the Principled SSS radius channels?)

michael campbell (3di) added a subscriber: michael campbell (3di).Apr 13 2021, 5:27 PM

should this be working now? I don't see a mention of it not being possible on the SSS node's page in the manual anymore. Still not working though, and I can't see any reason why just passing something values needs to be a limitation.

Evan Wilson (EAW) added a subscriber: Clément Foucault (fclem).Apr 13 2021, 5:57 PM

Hey @michael campbell (3di),
The limitation is listed under “Supported Nodes”.
https://docs.blender.org/manual/en/2.93/render/eevee/materials/nodes_support.html

As to why it is a limitation, I don’t know. You would have to ask @Clément Foucault (fclem).

michael campbell (3di) added a comment.Apr 13 2021, 6:25 PM

@Evan Wilson (EAW) , just spoke to him. It's just too difficult to fix unfortunately.

Philipp Oeser (lichtwerk) mentioned this in T96260: Eevee: Subsurface Scattering radius still uses the color information of default value if socket is connected.Mar 9 2022, 1:50 PM