SSS on GPU?

[aaron_ross]

Am I missing something? SSS in VRayMtl doesn't seem to be supported by V-Ray GPU 5 update 1. I'm using 3ds Max.

I tried both SSS and Volumetric Translucency.

I tried all the options in "Render Setup > V-Ray tab > Global Illumination". That includes Brute Force with 16 bounces, and "GPU Light Cache (WIP)". Still no love.

The documentation doesn't seem to mention anything about SSS not being supported on GPU.

To make matters worse, the preview swatch in the Material Editor shows the SSS effect, whereas the VFB does not. I guess the Material Editor always uses the CPU, even though it's set to GPU in "Render Setup > Common > Assign Renderer"? Super confusing. Apparently preview swatches must be drawn by the CPU? The GPU can only run inside the VFB or viewport?

[fixeighted]

Oddly, it will actually work and update and look like the swatch if you set the refraction to white (contrary to cpu where it must be black). And then the colour and amount are greyed out.
So that is a bit confusing

[aaron_ross]

Oddly, it will actually work and update and look like the swatch if you set the refraction to white (contrary to cpu where it must be black). And then the colour and amount are greyed out.
So that is a bit confusing

That is absolutely not working for me. Setting Refract to white gives full transparency with no SSS regardless of the Translucency mode.

My understanding is that a non-zero Refract color is for transmission, not subsurface scattering. The Fog Color sets the color of transmission.

The UI is confusing here, because refraction, transmission, and subsurface scattering are three different things. But they are jumbled up together in the UI, and the attributes interact in non-intuitive ways.

So I repeat, V-RayMtl SSS is not supported on the GPU, but this is not mentioned in the documentation.

VRayALSurfaceMtl and FastSSS work fine on GPU, so that's a partial workaround.

[fixeighted]

It doesn't work. I got mixed up in testing and with other posts on similar stuff.
All gpu will do is the regular fog effect, hence the other parts being greyed.
It may have made it to the docs today - haven't looked, but I think it's mentioned in the
announcements post for 5.1.

[aaron_ross]

Great, thanks for the verification.

[piotrus3333]

Am I missing something? SSS in VRayMtl doesn't seem to be supported by V-Ray GPU 5 update 1. I'm using 3ds Max.

I tried both SSS and Volumetric Translucency.

I tried all the options in "Render Setup > V-Ray tab > Global Illumination". That includes Brute Force with 16 bounces, and "GPU Light Cache (WIP)". Still no love.

The documentation doesn't seem to mention anything about SSS not being supported on GPU.

To make matters worse, the preview swatch in the Material Editor shows the SSS effect, whereas the VFB does not. I guess the Material Editor always uses the CPU, even though it's set to GPU in "Render Setup > Common > Assign Renderer"? Super confusing. Apparently preview swatches must be drawn by the CPU? The GPU can only run inside the VFB or viewport?

correct, swatches are rendered on cpu. I did not find a way to change this behaviour in 3ds max even with “custom sample object”.
for now you are limited to VRayFastSSS2 (on its own or as part of additive VRayBlendMtl)

edit: or AlSurface but I have no experience with this one.