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Karma XPU noise

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jumax
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I am trying to render something in Karma XPU and I can't seem to get rid of the noise. Just for a test I left it running with super high pathtraced samples and reflection and refraction limit and as you can see at 30 mins I am still getting noise on the edges of the bottle. I know I can use the denoiser but I am trying to understand the settings a bit.

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image_2024-02-22_100740695.png (1.5 MB)

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jumax
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For some reason in the screen shot the noise is not apparent but its there.
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jumax
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with a reduced limits

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karma.png (2.1 MB)

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jumax
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so 7 mins 512 path traced samples and 16 samples on the limits this is where I am at.

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jumax
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no one has experienced this?
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brians
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There is a lot of color noise in the water droplets. Do you think that's coming from the domelight?
Or do you perhaps have dispersion enabled? (dispersion is known for noise, given it needs to split a ray up into separate wavelengths)

Have you tried a denoiser to reduce the noise?
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jumax
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Hi Brian

I have tried various lighting setups and shaders, with and without dispersion but it seems XPU is not capable to remove noise without denoiser. I am trying to understand how the settings work so I am not using the denoiser at the moment.

In the attached image have 512 path traced samples and 6 light samples even after 9 mins there is no resolution. in the previous examples I let it run for 30 mins and there was not enough improvement.
Edited by jumax - Feb. 26, 2024 02:13:22

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brians
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I wonder if the forum is compressing these images or something, because I'm not seeing much noise. Could you attach them in a .zip file instead? (then hopefully I can just download).

Another thought, what happens if you turn off the lighttree? (ie back to uniform sampling for the lights)

thanks
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jumax
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I am trying with the light tree turned off but its not looking promising, at 2 mins its still pretty grainy. I dont understand why it wont clear up with super high samples and taking so much time.

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denoisedimage.zip (849.7 KB)

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jsmack
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jumax
In the attached image have 512 path traced samples and 6 light samples even after 9 mins there is no resolution. in the previous examples I let it run for 30 mins and there was not enough improvement.

512 samples isn't very many. Some paths could take 10s to 100s of thousands of samples to clean up.
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jumax
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I have tried it at 4096 samples it took like 30-40 mins and the result weren't getting better, its pretty slow if it can't resolve in that time. Its a pretty basic scene. I guess with XPU have to use the denoiser. I am running a render with 50k samples lets see what that does,
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ronald_a
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This does not seem right, especially for the simple shaders version. Submit an RFE and include the scene so Sidefx can take look.
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