Scanlines Visible with multi GPU + Fur

[rusteberg]

Hi, I'm using vray hair/fur to soften clouds. I've got these scanlines that started appearing when using multi gpu in vantage and it appears to be hair/fur causing it. Here's some examples:

This is in 2.3 with 551.86 driver using a 4090 and a 3090

[rusteberg]

happens at a certain threshold between per area density and hair thickness - depending what object it's applied to

[rusteberg]

Here's some results I was getting before enabling second gpu

[vladimir.nedev]

Do you see any warnings in the log ?
Something that starts with "VRayFur hair generation".

Greetings,
Vladimir Nedev

[rusteberg]

hmmmm.... lemme look and see

[rusteberg]

Here's the two warnings that appear:

08:01:37.968 [Wrn] Warning: Disabled light cache because it produces artifacts in multi-GPU setups.
08:01:37.968 [Wrn] Warning: Disabled RTXDI resampling because it's not supported on multi-GPU setups.

Only hair warnings that do come up, if any, are limits on the 50million strands enabled by default. However, I can't see those scan lines appear on anything other than dense hair/fur

Here's a simple scene that does it: https://wanderplay.com/stuff/Vantage...nLines.vrscene

Let me know if this helps -T

[Luma3d]

Is this with the latest Vantage update?

[vladimir.nedev]

Here's a simple scene that does it: https://wanderplay.com/stuff/Vantage...nLines.vrscene

I tried on 2 RTX 8000s and don't see the issue.
Is there anything I have to do after opening the scene ?

If it's possible, can you send me the vantage.ini and defaults.vantage files from %appdata%/Chaos Group/Vantage.
This way I can test with the exact same settings. Also if you have a specific .vantage file for the scene.

Greetings,
Vladimir Nedev

[vasile_bulgac1]

I don't know if I'm correct or wrong but you're using two GPUs with two different architectures. RTX GeForce 3090 is based on the Ampere architecture, which features Nvidia's second-generation ray tracing (RT) cores and third-generation Tensor Cores and the RTX GeForce 4090 is based on Nvidia's Ada Lovelace architecture and feature Nvidia's third-generation RT cores for hardware-accelerated ray tracing (RTX), and fourth-generation deep-learning-focused Tensor Cores... Let's not forget NVLink is no longer supported on the Ada Lovelace GPU architecture that powers Nvidia's flagship RTX 4090 GPU.

I'd suggest you to try to render with only one GPU but not with one disabled, try to remove it from the mobo and see if you encounter these scanlines.

These days Multi-GPU is more a pain than a gain, that's why I have opted and bought a RTX 6000 Ada and frankly Vantage works like a charm, 8K renders are no longer a dream

[vasile_bulgac1]

I tried on 2 RTX 8000s and don't see the issue.
Is there anything I have to do after opening the scene ?

If it's possible, can you send me the vantage.ini and defaults.vantage files from %appdata%/Chaos Group/Vantage.
This way I can test with the exact same settings. Also if you have a specific .vantage file for the scene.

Greetings,
Vladimir Nedev

You may not see the issue because you're using two RTX 8000 which are based on the Turing architecture and they support NVLink...I'm not 100% sure but from my past experience with the GPUs I might be right.

[npg]

I'd suggest you to try to render with only one GPU but not with one disabled, try to remove it from the mobo and see if you encounter these scanlines.

It will certainly work because these are multi-gpu artifacts for sure. No need to touch the hardware - we have device settings in Edit->Render Devices.

[vladimir.nedev]

You may not see the issue because you're using two RTX 8000 which are based on the Turing architecture and they support NVLink...I'm not 100% sure but from my past experience with the GPUs I might be right.

The fur shouldn't be that much different on the 3090 and 4090.
It looks completely different on one of them in his renders.
We don't have that setup however to test easily.

Greetings,
Vladimir Nedev

[rusteberg]

I tried on 2 RTX 8000s and don't see the issue.
Is there anything I have to do after opening the scene ?

If it's possible, can you send me the vantage.ini and defaults.vantage files from %appdata%/Chaos Group/Vantage.
This way I can test with the exact same settings. Also if you have a specific .vantage file for the scene.

Greetings,
Vladimir Nedev

Hey Vladimir, I can look for those two files and email them to you. If/when occurs again I'll pack a scene for you to look at. Thanks!

[rusteberg]

Here you go:

I sent the scene for this along with the ini and vantage defaults through support ticket number 243962

Hope this helps! -T

[tashko.zashev]

Thank you for the files!
The issue was reproduced successfully here.