Matte Objects, alpha contribution and SSS

[francomanko]

So objects with an SSS material, using the matte object setting and alpha contribution of -1.0, still render (the SSS color) and still show up in the alpha. Is this a bug or just not supported?

Using max2024, latest vray, recommended drivers etc.

[Philip Shounev]

Hello,

Could you provide more details about your setup like screenshots or a scene sample? When I create a simple scene setup containing the above-mentioned components, matte objects shaded with an SSS material are working as expected on my end.

[francomanko]

maybe im doing something wrong. Anyway ive attached a scene, the sphere in front is the matte object with Vrymtl and SSS turned on. When you render its white. (SSS color)

Thanks

[fixeighted]

I think it just doesn't work using GPU, as it's fine with cpu.
Oddly, using GPU, it will gradually disappear as you lower the SSS amount, which is not the point ofc, just noticed it is all

[francomanko]

I'm getting similar issues with materials with metalvalues of 1, but that seems to be something in my scene, will have to investigate further

[Philip Shounev]

Thank you for providing a scene sample. The issue indeed occurs specifically with V-Ray GPU when using either VRayFastSSS2Mtl or VRayMtl with an SSS translucency. These are now logged in our internal bug-tracker under VGPU-6483.