Standard_surface Randomwalk2 SSS in HTOA looks different between GPU and CPU

[Anonymous]

Rendering skin with Randomwalk2 in GPU and I'm not getting the same beautiful look that Randomwalk2 provides under CPU rendering.

It's as if Randomwalk2 shuts off and GPU falls back to diffusion.

Anything I can do to get Randomwalk2 on GPU in HTOA?

[Slava_91 · Accepted solution]

Hi, Diffusion SSS is not supported on GPU. Can you attach screen with problem or wrote more information about it, what exactly happened, so you think this is diffusion?

[Anonymous]

Thanks for answering Slava -

I just tested in a new scene in prep for posing an A/B here for you, and GPU renders skin exactly the same as CPU now - I must have been doing something wrong in the previous scene.

All is good - this is beautiful skin shading done on the GPU.

[Anonymous]

Hi @slava

Actually I do still have an issue now that I've scaled the object down to 0.01 which I should have done before answering that everything was okay above. I think this is certainly regarding scene scale.

My human model (from Maya at 180cm) is scaled to 0.01 units in Houdini which would be the correct height of a human (1.8 meters).

Subsurface scale is set to 0.001 which looks somewhat "correct" using CPU based Randomwalk2.

Here is what that looks like in this quick test:

Here is the same asset rendered using GPU as a render device:

I'm scaling the asset using a transform sop under a file node and converting it to polygons.

[Anonymous]

Also here are the GPU / CPU logs if it helps you.

arnold_log_GPU.txt

arnold_log_CPU.txt

[Anonymous]

@leegriggs

I jumped the gun and accepted Slava's answer before scaling the model properly and reopening the issue, so didn't get a fix for this yet.

Please see the images and comments below ( I attached logs if it helps to decipher the possible scene scale issue)

[403504414]

It could be an issue with the render settings not being set correctly. It is correct to set the system export scale to 1cm in the rendering settings.