Arnold GPU - Can't get a noise free render when using Mesh Light or Emissive Material

[spencermullerdiniz]

Hi all,

I've been tinkering a bit with Arnold GPU renderer and I can't get results equivalent to CPU rendering when rendering a simple scene that contains mesh lights or emissive materials.

I get a lot of noise from mesh lights or emissive materials when using GPU rendering.

I followed all of the suggestions regarding AA samples and adaptive sampling, but still get a very noise result when using GPU renderer.

See tests below.

Any ideas how to fix this?

GPU Renderer:

GPU Renderer (Adaptive Sampling / 100 AA Samples Max / Adaptive Threshold: 0,01

CPU Renderer:

[JohnDraisey]

I'm curious now, I'll see if I can recreate this issue.

[madsd]

I just tested it in the latest build, I cant repo, with either emissive or mesh lamp, they both come out clean after some seconds.
The emissive stops premature however, and it does not respect adaptive high samples, it looks like its clamped, but no fireflies, it just stops iterating

[Anonymous]

Can you add the test scene?

On Arnold version 3.1.26 it runs fine.

[spencermullerdiniz]

Hi all,

Here's the test scene and also the latest render using version 3.1.30.

Still reproducible.

Since I'm getting an error uploading the file ("Error parsing uploaded file" ), here's a download link:

TestScene.zip

Thanks,

Spencer

[madsd · Accepted solution]

I was able to correct the issue.

You use Linear exposure which for some reason introduces a ton of fireflies.
Setting to non or Physical instantly removes them.

Yeah so I can actually go back to linear, after some thing has been reset. and fireflies are gone.
So it seems you have injected a glitch into the file, that can be reset with this simple manouver.

https://imgur.com/a/xAczlb

[spencermullerdiniz]

Nice! Thanks for taking the time, @Mads Drøschler.
I'm very amateur and would never think that exposure settings could affect a render this way.

[spencermullerdiniz]

@Mads Drøschler, just got home from work and tried the workaround you proposed (changing exposure control to physical), but I'm still getting noise + fireflies. The only way I can get rid of them is by using CPU rendering.

Can you share the fixed scene file so I can check it out... See if it works on my end.

[madsd]

https://www.dropbox.com/s/sjimmty0ppdsr44/lamps.zip?dl=0

2 scenes 2 different setup.

Also, I added a screenshot to show you how to manage fireflies in general.
You lower the Indirect AA clamp from 10 down to 3-4 or 2 if you want to dig deeper.

[spencermullerdiniz]

I used the files you sent and compared with my original scene.

Seems quite a few things changed, but what really made the difference was increasing the intensity of the mesh light. In the end, I changed exposure to Physical Camera and tweaked the intensity of the mesh light to get a total intensity of around 16000. Intensities lower than this would start rendering fireflies.

Thanks for taking the time...

[Anonymous]

Hello. I finally got gpu for rendering. You have to set clamping to minimum. Then you will have exact render as cpu. Cheers.

[spencermullerdiniz]

What clamping are you referring to @vedran?

[lee_griggs]

GPU or CPU, intersecting lights with geometry is not recommended.

[Anonymous]

Under adaptive sampling in Maya 2020. But then reflections are black. No good. I also have ton of fireflies. I don't know why. I will ask a pro.

[Anonymous]

Hello, I also have ton of fireflies with gpu. I use only directional light. Can you please help? I use Maya 2020. Thank you.

[madsd]

Create a new thread so we don't need to do it in a nested dialouge on a case that is solved.

Remember to post images and descriptions of your problems as detailed as you can understand/get the situation.

[Anonymous]

how can we do this in houdini?