Very slow LC (GPU) and big difference between Cuda and RTX renders

[BBB3]

I have a relatively large production scene where the LC takes about 10 minutes to calculate on an HD still.
Also, Cuda and RTX give completely different results, with RTX appearing to be buggy.
I have an archived scene, who should I send it to?

EDIT: The RTX vs Cuda problem als occurs in the latest stable hotfix of V-Ray 5, though not in versions prior to that.

[Muhammed_Hamed]

Hi Bertrand,

what happens if you turn off the preview for GPU LC in settings?
what about GPU memory usage, does it peak to the VRAM ceiling on rendering the scene?

could also try with material overrides, with a simple V-Ray material.. the slow down might be about one of the shaders in the scene
It will be best to take a look at the scene, or a simplified version.

About the Cuda/RTX differences, could you please share some renders?
Are you using Cuda x86 ? or Cuda GPU ?

Best,
Muhammed

[^Lele^]

I have an archived scene, who should I send it to?

I'd say send it to Support, mention this thread.

Muhammed_Hamed As a side request, would you mind using the default font size for the forums?
Every time i try and read one of your posts, on the screen i'm on (a big one), i have to make double the effort, as there's hardly any text per line.
Besides the fact it seems you're yelling at me. ^^
If anyone needs bigger text, they can ctrl+scroll on most browsers.
Ofc, if there are overruling reasons, ignore me.

[BBB3]

Thanks guys. I've uninstalled V6 now and switched back to V5 but I can sent support a GDrive link to the archive (Max 2022) if you want to try it.

[^Lele^]

Please, and thank you.

[BBB3]

About the Cuda/RTX differences, could you please share some renders?
Are you using Cuda x86 ? or Cuda GPU ?

Cuda performs as it should, it's the RTX version that seems to be buggy.

These are V5 renders but the problem persists in V6 (RTX is left, Cuda is right).

I've sent the scene to support and mentioned the thread.

The super long LC calculation is specific to V6. LC is fast in V5.

[Muhammed_Hamed]

What drivers are you using? BBB3
The geometry artifacts were fixed on Nvidia's side a while back, starting 495 drivers. Otherwise this could be a different issue

Thanks for all information, we will investigate and report back

Best,
Muhammed

[Muhammed_Hamed]

Besides the fact it seems you're yelling at me. ^^

What do you mean, I don't think I have the heart to do such thing <3
I may or may not yell at things, but I never yell at Lele

This is what it looks like for me
the text is soo tiny except for my own, it is also a visual indication to my find my own comments (faster)



I will use normal size from now on, lets see how this goes.
Although I think we could do a better job with font size, I had many comments about that recently haha

[^Lele^]

What do you mean, I don't think I have the heart to do such thing <3
I may or may not yell at things, but I never yell at Lele

LOL, give it a while, you'll get the hang of it!

I have a 55" screen and a 150% default zoom in Chrome, so a capital A at the size you used was about .8CM tall.
By the end of a post, i was trying to catch up with the twisting of my neck... XD
So long as everything is the same (say, within a page/article) then default zoom settings can correct for most issues, i'd think.
Thanks for trying it out smaller, btw.

[Muhammed_Hamed]

^Lele^ haha, I realize my mistake now. sorry about that, it is just one old habit on using the forum
Thanks for the tip on 150% zoom, it seems to work well so far

[BBB3]

What drivers are you using? BBB3
The geometry artifacts were fixed on Nvidia's side a while back, starting 495 drivers. Otherwise this could be a different issue

I'm using 512.15 right now. These artefacts are the reason I updated the driver but it didn't make any difference. This seems to be a problem with the shader rather than something to do with geometry.

[BBB3]

Anything you guys could glean from that scene file?

[^Lele^]

Anything you guys could glean from that scene file?

We hit a snag with support (believe it or not, a bug! So thanks for helping us find it.), and the scene seemed lost.
We have however found it, thanks to the investigative work of svetlozar.draganov , and i sent you an access request to the gDrive link from my chaos email.

[BBB3]

We hit a snag with support (believe it or not, a bug! So thanks for helping us find it.), and the scene seemed lost.
We have however found it, thanks to the investigative work of svetlozar.draganov , and i sent you an access request to the gDrive link from my chaos email.

thanks Lele. Just shared the folder with you.

[Muhammed_Hamed]

Hey Bertrand,

We took a look at your scene, we are able to reproduce the artifacts with RTX mode. It is logged under VGPU-5848
The issue is tied to one bitmap in the scene "Map #95", and the "invert" toggle in its output (walls base material's diffuse texture's radius).
Turning inversion off (or the whole texture, plugged into the vrayDirt radius) fixes the issue. You can use this as a workaround for now(thanks to Lele for investigating that)

We couldn't reproduce any LC issues with V5 or V6, it calculates very fast on my side. I tested on 3080 Ti and 3090, and Lele tested on 2080 Ti
There is one more issue with blocky shadows in the scene, I logged as well VGPU-5849

Best,
Muhammed