Karma volume sampling, how to get a clean image?

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Hello,

I have a big issue getting a noise free render with the karma volume shader.

It's a simple scene with some clouds (based of some of your templates), a karma volume material and a physical sky. When I render it (on our farm) it feels like it reaches a limit no matter what settings I increase and it just looks fairly undersampled.

I'm using XPU and the render settings I've increased are

pathtraced samples 128->1024
lightsampling quality 1->5
volume step rate .25->1

all the limits have been upped. the only one I found had an effect is the obvious one, volume limit. it actually affects the noise in the image but up until a certain point, after 5-6 limits, the noise stays the same. After trying various parameters one by one it also seems like it's the only one really doing any effect on the image.

Here is a simple screen of the max level I can clean the noise to:



Thanks for any comment and answer, I'm sure it's just me who is new to karma and missed something obvious but I just can't find what it is. Things I can think of is if I've missed some threshold parameter or similar.

Using H20.5 but have access to 21.

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Screenshot at 2025-09-09 11-16-09.png (141.3 KB)

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Try tweaking the variance-oracle settings (or disable it completely)
Edited by brians - today 16:31:45
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