EEVEE, subsurface scattering and render passes?

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1

Hi!
Today I’ve been having an issue with subsurface scattering and compositing in Eevee. Here are the conditions to cause the problem:

  • Eevee as a renderer
  • having an object using subsurface scattering
  • having screen space reflections enabled and half res tracing disabled (using this option solves the problem, but of course degrades the quality)
  • composing the render passes manually and not using the “combined” render output

To mix the render passes, I don’t do anything special: Diffdir multiplies DiffCol, GlossDir multiplies Glosscol, and their results are added.

This is what I get (using a test file I’ve created showing the issue):

image
image706×709 42.9 KB

This is what I should get:

image
image699×706 46.4 KB

What is the issue here? If I check the single passes, they already seem to display that artifact. And the artifact disappears if I enable half res trace. Also, Cycles works just fine, I can mix all passes without this artifact appearing.

Does anyone have an idea? I’m sure this is actually something very silly… thank you in advance!

FILE:

sstest.blend (2.2 MB)

2

Hi Matteo,

This of any help . . . ?

image
image2446×1266 306 KB

Cheers,
Dj

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3

Thank you so much for your answer! I confess I had overlooked it. It does help in that circumstance, since the roughness is constant. I had, however, also another case where the roughness is not uniform (that’s how I originally stumbled upon this problem):

sstest.blend (2.2 MB)

image
image880×882 101 KB

how it looks

image
image712×702 48.1 KB

how it should look?

In a case where the roughness is quite contrasty, I can’t make it work! Most likely, I am once again overlooking something…

4

Just in case someone stumbles upon this: I have reported it as a bug to Blender and it has been confirmed. We shall see how this develops!

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