Principled BSDF handles roughness incorrectly #96527

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tempdevnova · 2022-03-16T17:41:52+01:00

tempdevnova commented

2022-03-16 17:41:52 +01:00

System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.07

Blender Version
Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: blender/blender@f1cca30557
Worked: (newest version of Blender that worked as expected)

Short description of error
The Blender docs states for the Principled BSDF roughness: When converting from the older Glossy BSDF node, use the square root of the original value.
https://docs.blender.org/manual/en/latest/render/shader_nodes/shader/principled.html

However when doing testing I have found, that to get equal results the Principled BSDF needs exactly the same roughness values as the glossy shader.
Same is also applicable with transmission roughnes and the refraction/glass shader.

Exact steps for others to reproduce the error
This test file clearly demonstrates this in the case of glossy roughness:
Test file.blend

Is maybe just the documentation outdated?

Thank you and have a great day!

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.07 **Blender Version** Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: `blender/blender@f1cca30557` Worked: (newest version of Blender that worked as expected) **Short description of error** The Blender docs states for the Principled BSDF roughness: `When converting from the older Glossy BSDF node, use the square root of the original value.` https://docs.blender.org/manual/en/latest/render/shader_nodes/shader/principled.html However when doing testing I have found, that to get equal results the Principled BSDF needs exactly the same roughness values as the glossy shader. Same is also applicable with transmission roughnes and the refraction/glass shader. **Exact steps for others to reproduce the error** This test file clearly demonstrates this in the case of glossy roughness: [Test file.blend](https://archive.blender.org/developer/F12930381/Test_file.blend) Is maybe just the documentation outdated? Thank you and have a great day!

tempdevnova commented

2022-03-16 17:41:52 +01:00

Added subscriber: @tempdevnova

Germano Cavalcante commented

2022-03-17 15:47:57 +01:00

Added subscribers: @angavrilov, @mano-wii

Germano Cavalcante commented

2022-03-17 15:47:57 +01:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Germano Cavalcante commented

2022-03-17 15:47:57 +01:00

This is the result seen in Blender 2.79

The Hint was added in {rBM3542} by @angavrilov
Does the "older" in "older Glossy BSDF node" mean the node from older versions of Blender?
If so, this needs to be made clearer to avoid confusion. Otherwise it seems best to just remove that Hint.

This is the result seen in Blender 2.79 ![image.png](https://archive.blender.org/developer/F12931949/image.png) The `Hint` was added in {rBM3542} by @angavrilov Does the "older" in "older Glossy BSDF node" mean the node from older versions of Blender? If so, this needs to be made clearer to avoid confusion. Otherwise it seems best to just remove that `Hint`.

blender-admin commented

2022-03-17 15:59:05 +01:00

This issue was referenced by 9130