VrayMtl SSS Translucency scatter radius cuttoff

[frodopytlicek]

Hello there,
did someone have same problem with using gradient textures in scatter radius of sss translucency? Im not realy sure where could be a problem.

[vlado]

A zero value for the scattering radius is not quite valid; I think we turn off the SSS effect in that case. Perhaps we should clamp it to some small value instead?

Best regards,
Vlado

[frodopytlicek]

Aaah interesting clamping absolute black values to some small one fixed the problem. Great. To clarify my inted, I want to achieve something like sss mix in ALSurfaceMtl. Maybe you have better way to do this? Because SSS amoutn cannot be mapped to texture :/

[frodopytlicek]

Hmm but I'm also noticed facing issue with SSS translucency :/ What is that?

[fixeighted]

I can't find the relevant post but the facets can be fixed by adding a VrayDisplacement mod and setting the amount to zero (or it adds a default bump).

[frodopytlicek]

Adding subdis will not fix it it will just make it less visible because the faces become smaller.

[fixeighted]

That was Vlado's fix for it when I asked, so not sure what else to suggest.

[^Lele^]

Adding subdis will not fix it it will just make it less visible because the faces become smaller.

Correct.
Set the edge length small enough (f.e. 1px in screen space), and the triangles won't show.
SSS doesn't do smoothed (interpolated) normals.

[frodopytlicek]

Correct.
Set the edge length small enough (f.e. 1px in screen space), and the triangles won't show.
SSS doesn't do smoothed (interpolated) normals.

Ok but FastSSS and ALSurface doesnt do this. So it some sort of known bug which will be fixed id future? I thought that movig SSS to VrayMtl is step to overcome ALSurface and FastSSS

[^Lele^]

It's a different SSS method: more accurate, but with this limitation, which is however essentially non-existent for character work, f.e., and any other displaced geometry.
This is the same for every engine implementing a true random walk approach.
You have the options, though, should your surface be simple by design or requirement.

[frodopytlicek]

Understand. Thanks a lot for explanation.