Anisotropy artifact in CPU but not in CUDA

V-Ray V-Ray for Maya Issues
1

Hey everyone,

I am seeing some really weird artifacting when I use anisotropy on the vraymtl, and I cannot figure out why. I am using Vray 3.4. I have tried different brdfs, different sampling, new geo, different amounts of subdvisions, sampling cutoffs, etc.. The really weird thing is, this only occurs when I render on the CPU, but when I use my GPU either in production render or as RT, the problem disappears. However, even when rendering with CUDA, the artifacting still appears in the few couple of passes, but then disappears completely. See attached images.

There is also a noticeable difference in reflection appearance between CPU and CUDA.

Any ideas?

CPU:

CUDA first pass:

CUDA end:

wireframe:

anisotropy.jpg
anisotropy.jpg943×530 47.2 KB

cuda_beginning.jpg
cuda_beginning.jpg943×530 262 KB

CUDA_end.jpg
CUDA_end.jpg943×530 145 KB

wireframe.jpg
wireframe.jpg943×530 161 KB

2

Still unable to figure this out. Anyone have any suggestions? Thanks!

3

maybe post a scene for us to look at.

4

Yes, a scene will be very helpful.

Best regards,
Vlado

5

Awesome, thank you! Attached is the scene file I am having trouble with.
The result is definitely changing when I adjust smoothing amount, but it never goes away, and still isn’t present in rt, so that might have something to do with it?
anisotropy_problem.zip (334 KB)

render.jpg
render.jpg943×530 30.1 KB

6

There seems to be the lower glossiness values + anisotropy involved in this. I’ll put a note so our developers can have a look.

7

@thebeals

If you have access to the nightly builds, you can try an older build i.e. from November 22nd. The issue doesn’t occur with it.

8

Awesome, thank you for taking a look into it!