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Maniphest T70915

Diffuse materials glow in corners or small gaps when using Principled Shader in Cycles
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Description

System Information
Operating system: Linux Mint 19.2
Graphics card: 1080 Ti

Blender Version
Broken: 2.80, cycles

Short description of error

Diffuse materials glow in corners or small gaps when using Principled Shader. I am not sure it is bug or correct behavior, but issue is gone if color value (V from HSV) is decreased to 0.9, or Diffuse shader is used instead. Decreasing roughness and specular also helps but that will make totally different material.

Exact steps for others to reproduce the error
Here are image and blend file

diffuse_light.blend694 KBDownload
,

Event Timeline

Tautvydas Andrikys (esminis) created this task.Oct 18 2019, 9:30 AM
Tautvydas Andrikys (esminis) added projects: Render & Cycles, Cycles.
Brecht Van Lommel (brecht) changed the task status from Unknown Status to Unknown Status.Nov 6 2019, 4:47 PM
Brecht Van Lommel (brecht) claimed this task.
Brecht Van Lommel (brecht) added a subscriber: Brecht Van Lommel (brecht).

Diffuse materials with reflectivity 1.0 are unrealistic, and this kind of glowing can actually be accurate for the given parameters.

Tautvydas Andrikys (esminis) added a comment.EditedNov 6 2019, 5:31 PM

Hm did I miss something - it has roughness 1.0, specular 0.5, metlaness 0.0 - where does reflectivity 1.0 come from?

Brecht Van Lommel (brecht) added a comment.EditedNov 6 2019, 5:36 PM

It's the base color that has 1.0 for some channels.

Steffen Dünner (SteffenD) added a subscriber: Steffen Dünner (SteffenD).Nov 6 2019, 5:46 PM

Here's your original material with a diffuse of HSV 0.5, 0.5, 1.0:

And here's the same scene with diffuse HSV 0.5, 0.5, 0.8:

Tautvydas Andrikys (esminis) added a comment.Nov 6 2019, 6:04 PM

Ah so essentially pure color is bad to use - I should decrease V to make color little bit darker, thanks ;)