Vray GPU = Displacement Aliasing Bug/Artefact

[FranklinTre]

Hello everyone,

I'm having an issue with Vray GPU, both with Vray Next 1 and 2, the release from yesterday. I'm struggling with it, I don't find any explanations on the web, and I'm sure there is something I can do !

I made a simple material, just an Albedo Map and a Displace Map (in the displace slot); both from the Megascans library, in 4K.
The light is a simple Vray Sun, all parameters are the standard ones.

With Vray GPU I get some lines/strata/artefacts, image 1.
With Vray CPU, I don't get the lines/strata/artefacts, image 2.
With Vray GPU, I don't get the lines/strata/artefacts if I set the image blur to 0.01, image 3.

Is anyone can explain to me why is it doing this things in GPU? It is not doing anything like that with a standard noise in the displace slot, for example.
It's a big trouble for me because of my workflow. I use TryplanarTex to move coordinates (I know it's a trick...) but the Tryplanar discard the Blur option from the bitamp source ...

Thanks in advance, and excuse my english, it's not my first language !

IMAGE 1 : Default + GPU

IMAGE 2 efault + CPU

IMAGE 3 : no blur + GPU

[FranklinTre]

Up !

No one as a clue ? I mean, it's a general huge issue ...
No displacement map is working correctly without setting the blur to 0.01, which is higly not recommended by Chaos.

[hristo.dimitrov]

Can you please send us a simple scene with the issue to support@chaosgroup.com for investigation?

[rwcantrell]

Was there any resolution on this issue? I am running into a seemingly similar issue now on Vray 5 hotfix 2 for 3dsMax with bump maps. The same scene rendered in CPU produces much more smooth results, while the GPU render looks heavily aliased. The input image is the same black and white bump map 16 bit, 8k with "None" color space.

Thanks,

[FranklinTre]

I still have the issue with the last version.
It's not happening with a noise or celullar map, so I think its coming from the interpretation of the "bluriness" of the map.

But I have no clue otherwise...

[rwcantrell]

Thank you for the insight. I also tested with the latest 3dsmax stable nightly build (5.00.06 build 30505) and it did not change the previous incorrect aliased bump map findings. So far, no combination of changes to the filtering or interpolation options when using Vray's Bitmap node of 3dsmax's bitmap node has had any affect on the images rendered with GPU.

However, converting the grayscale bump map to a normal map in a 3rd party software provides smooth results in both CPU and GPU modes. Although, this is not ideal for later steps in the material workflow.

[FranklinTre]

Up Here

The situation is worst than before.

Now those lines, this aliasing is happening all the time with some map. The tweak of putting the blur to 0,01 is not working anymore since this is by default with the VrayBitmap.

Do your team as a clue about what happening here ? Its clearly a big issue with a lot of materials anytime you need to do a close shot.

Regards.

[nikoleta.garkova]

Hi FranklinTre

Please forward a scene with the issue reproducible through our contact form so we can investigate further. Make sure to mention this thread in the email along with information about the exact V-Ray/3ds max version and details regarding your CPU/GPU/GPU driver version. Much appreciated.