FastSSS2 - Diffuse Amount

[JonasNöll]

Hi,
I am getting a problem that the lighting channel of FastSSS2 Material always contains diffuse lighting, even though the diffuse amount is set to 0.
From my understanding the lighting channel should be totally black in this case and the whole contribution should come from the subsurface scattering.
Or is this expected behavior? The ALSurfaceMtl does not have this issue and the lighting channel turns to black when SSSMix is set to 1.

[^Lele^]

It's expected.
SSS in the original shader is mixed with diffuse.
No diffuse, no SSS.

[JonasNöll]

Hi, thx for the reply.
Somehow I rendered the same with 3.6 and my lighting is completely black how I would expect it.
It probably has to do with the consistent lighting elements which split up lighting and GI differently in later V-Ray versions. So some of the GI is also in the lighting element now with consistent lighting elements.
The weird thing is that if even I disable GI entirely I still have something showing up in the lighting in 2021 V-Ray 5.
But in 2018 3.6 in this case both lighting and GI are totally black.
Has the way how this information is being split up somehow changed? Maybe before what is left over in the lighting also got merged in the sss2 renderlayer in earlier versions?

[^Lele^]

You're right, i had *totally* misread the problem.
I'm not sure what ends up in lighting right now. Will ask the devs as the holidays end.

[^Lele^]

So, the Lighting RE will contain the primary scatter of the shader, *if* the shader scatter mode is set to simple.
It will be black if the scatter mode is set to raytraced (either of them.).

[JonasNöll]

Alright great, thanks for the clarification! I will test that out!

[JonasNöll]

Alright, I can confirm that the weird leftover part in the lighting disappears when selecting raytraced (GI disabled). Also when enabling Scatter GI the Lighting and GI passes become totally black when GI is enabled. It's just weird that it's not the same as with earlier verisons but thats probably because of the new Consistent Lighting Elements which split the information differently.
Anyway everything works as expeted now, thx

[^Lele^]

I was told the SSS shader went through a few revisions over the years, so it's possible something changed due to client requests, or technical limitations.
This one isn't specifically tied to the consistent REs, though, it happened before those (you can double check, if you turn them off. it'll behave the same way.).