Vray Next GPU, Black artifacts with some of the fabric scans

[Muhammed_Hamed]

Hi,

I noticed these artifacts with some fabric scans on Vray Next GPU
RT CPU will render them fine, but on GPU I get this result,
This happens with like 80% of the fabric scans that I tested, But few other fabric scans will render just fine.



Scan used,
https://download.chaosgroup.com/vrsc...9/fabric-red-s

How to reproduce,
Download my Shaderball scene here and apply the scan material to the cloths piece,
https://drive.google.com/file/d/1a-B...ew?usp=sharing

System specs,
Windows 10 1809
Maya 2018.4
Vray Next for Maya hotfix 1
GTX 1080Ti x 3
Nvidia drivers 416.94

I also tried on my Imac Pro and I can reproduce the same behavior,
OSX 10.13.6 High Sierra
Maya 2018.4
Vray Next for Maya hotfix 1
GTX 1080Ti
Web drivers,

387.10.10.10.40.108

Thanks for your help!

[Ivaylo Katev]

Thanks for the report Muhammed!
Just to clarify - under "black aretifacts" you understand these two vertical slits didn't you? We will download and investigate the scene, but perhaps the GPU team will investigate the problem, so until they start you can help us answering some quastios:
- Is the problem related to the "edges displacement" option, i.e. is it dissapearing if the option is disabled or enabled?
- Is the problem related to the transparency, i.e. what happens if you disable/enable it?
- is the fabric geometry confined or is just a deformed plane ?

[Muhammed_Hamed]

Hi Ivaylo and thanks for your reply!

Just to clarify - under "black aretifacts" you understand these two vertical slits didn't you?

Yeah, the vertical slits are what I meant. Sorry for bad English.

- Is the problem related to the transparency, i.e. what happens if you disable/enable it?

I get the same behavior turning it on/off
And by the way, these vertical slits don't show in light cache prepass.. it only shows after GPU buckets are finished or in IPR mode which doesn't use Light Cache

- is the fabric geometry confined or is just a deformed plane ?

It is not a plane.. The geometry has thickness and it is waterproof, but I just realized It has polysmoothSurface with subdivision set to 1
I did collapse the mesh, but still I get the exact same results
But if I set the polysmooth surface to 0 then collapse my mesh I get different kind of artifacts,

Hiding the geometry behind it, it seems the vertical slits are transparent, not black

Also here is another fabric scan that renders completely fine(20% of the fabrics will render fine without the slits, all leather scans will render fine too)

- Is the problem related to the "edges displacement" option, i.e. is it dissapearing if the option is disabled or enabled?

Where to find this option?

[Ivaylo Katev]

the edge displacement option is in the advanced panel

[Muhammed_Hamed]

the edge displacement option is in the advanced panel

Turning it off solved my issue!!
Thanks!

So should I turn it off for all my scans? or how should I use it?

[Ivaylo Katev]

this option produces small scale displacement on the visible edges, it can produce problems when applied over thin confined geometry