Eevees Principled BSDF handles external SSS radius values incorrectly #83006

New Issue

Jon Henry M. Faltis 9077149 · 2020-11-25T17:24:50+01:00

2020-11-25 17:24:50 +01:00

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: e922dd7d8a
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.blend

**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: `e922dd7d8a` 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. ![Eevee_PrincipledBSDF_SSS_Radius_Bug.jpg](https://archive.blender.org/developer/F9373451/Eevee_PrincipledBSDF_SSS_Radius_Bug.jpg) 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.blend](https://archive.blender.org/developer/F9373466/SSGI_SSS_Bug.blend)

Jon Henry M. Faltis 9077149 commented

2020-11-25 17:24:50 +01:00

Added subscriber: @geocentric_wage

Evan Wilson commented

2020-11-25 21:11:04 +01:00

Added subscriber: @EAW

Evan Wilson commented

2020-11-25 21:11:04 +01:00

Changed status from 'Needs Triage' to: 'Archived'

Evan Wilson closed this issue

2020-11-25 21:11:04 +01:00

Evan Wilson commented

2020-11-25 21:11:04 +01:00

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?)

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 commented

2021-04-13 17:27:05 +02:00

Added subscriber: @3di

michael campbell commented

2021-04-13 17:27:05 +02:00

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 commented

2021-04-13 17:57:15 +02:00

Added subscriber: @fclem

Evan Wilson commented

2021-04-13 17:57:15 +02:00

Hey @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 @fclem.

Hey @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 @fclem.

michael campbell commented

2021-04-13 18:25:43 +02:00

@EAW , just spoke to him. It's just too difficult to fix unfortunately.

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Eevees Principled BSDF handles external SSS radius values incorrectly #83006