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(using blender2.82) hey guys i have been trying to add fog to my scene but when i do it i have a lot of noise in the image i tried to use blender default denoise but it made it worst because it added huge amount of blur in place of the noise i also tried to use intel AI denoiser but it did the same thing it didn't help here are the examples: here with no fog or denoiseenter image description here

and here with fog without denoiser: enter image description here

and finally here with denoising: enter image description here

how you see the grass get so smooth in bad way!! can any one help? i just want the noise gone without effecting the other objects !

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  • $\begingroup$ What method are you using to denoise? $\endgroup$
    – Allen Simpson
    Dec 2, 2020 at 4:00
  • $\begingroup$ it is the same result with the INTEL AI denoiser and blender default version $\endgroup$
    – NiceSHowMoe
    Dec 2, 2020 at 4:01
  • $\begingroup$ but if you mean the last image i used the AI version $\endgroup$
    – NiceSHowMoe
    Dec 2, 2020 at 4:01
  • $\begingroup$ so the compositor node? $\endgroup$
    – Allen Simpson
    Dec 2, 2020 at 4:02
  • $\begingroup$ @AllenSimpson yes i used the compisitor node $\endgroup$
    – NiceSHowMoe
    Dec 2, 2020 at 4:03

1 Answer 1

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Denoisers are an imperfect, but useful tool.

I have this scene where there's light coming in through a window and I've given the room a volume to catch the light. If we run a low amount of samples you can see the fireflies produced.

enter image description here

This is normal, the nature of a volume with lower density is that it will only affect some rays cast from the camera. The denoiser gives us this ugly result:

enter image description here

with only little wisps of dust visible. This is also normal, because the denoiser can only work with the information we give it. I only ran this at 12 samples, and it is really interesting that it can produce this result.

Usually the answer is to run more samples, but even at 300 samples it comes out as this:

enter image description here

Which is part of the way there. I cranked a small region up to 1200 samples to turn this:

enter image description here

into this:

enter image description here

That's a lot of samples, but you can probably see from the noisy image that it would take many thousands of samples to render this volume in a realistic and pleasing way. Volumes with lesser density are just very noisy. The grass will be a lesser case of this, where more samples will give each pixel more influence over itself.

I did find in doing this that volumes aren't contributing to denoising normal or albedo, probably by design, but I wonder if it isn't related.

enter image description here

You may want to play with Adaptive Sampling instead, run some experiments with a render region.

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  • $\begingroup$ thanks for the answer :) $\endgroup$
    – NiceSHowMoe
    Dec 2, 2020 at 5:32
  • $\begingroup$ If this answer was helpful, please consider to accept and up-vote it @LightKnight How this site works: blender.stackexchange.com/tour $\endgroup$
    – brockmann
    Dec 2, 2020 at 8:37

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