Weird Post-Denoiser issue.
weikumsnc
Posts: 7
As the title states. I have a weird denoiser issue. I've render out 2 identical images at 4k quality at 1500 iterations. One has post-denoiser on, the other doesn't. The first picture (Has denoise on) Has weird spots that don't have any detail for some reason. The other (Has denoise off) Doesn't have the issue, but does have some grain left. My post denoiser is set to begin at 8 iterations. However testing showed that increaseing Post Denoiser Start Iteration to 1000 does not seem to fix the issue. I've had this issue previously once more but that time pixel filter radius was set to 0.85. Putting it to default value of 1.5 seemed to fix it. Pixel filter method was set to Mitchell. This time it didn't work.
Does someone have any idea what's going on? I'm not sure but I think this issue doesn't occur as heavily on 2k quality or even on 1080p.
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Comments
That's just the denoiser doing it's work in those very bright areas. You need more iterations to let it resolve. Or turn it off and live with the little bit of grain left in the second image.Or post process to combine the best parts of both images. Or post process the second image to apply some other denoiser software.
I see. I'll test out higher iterations. You mentioned other denoiser software. Got any recommendations? :)
Thanks for the reply.
For some reason the pictures were removed...
They are still there. I can see them. It is a forum bug; sometimes images in the first post get hidden.
Ok, so. I did another test, as you suggested with more and more iterations in each image. I went to 2000, then to 2500 and then to 3000. I will attach the images (A slightly different angle that gives a slightly different result).
It hasn't fixed the issue either.
Images go from 2000-2500-3000 respectively.
That's why Post Denoiser in DS seems a joke to me... (let alone comparing to the Denoiser in Blender...). No matter you set Start Iteration as 1, 500.... 2500, 2950, you'll get 99.9% same "denoising results".
I have no idea how to make a change as there's no other settings in Denoiser... but I just thought you wouldn't need Post Denoiser in such a scene with a very nice HDRI. There's no grainy noise to me. Adding some more Samples will be well enough.
Besides, the serious side-effect is that Denoise ruins your render by blurring the details rediculously ... If the details are "destroyed" by Denoiser, you have no way to recover them. So, I personally suggest not use Denoiser in DS.
Then, there's no 100% perfect Denoising software (stated as "bring you lossless quality"...) but you may try Topaz Photo AI... or Google denoiser from Github.
Try setting the post denoiser to start at the edge of the end iterations (for example if your iterations are set to 1500, start the denoiser at 1495). Should do the trick as the denoiser doesn't need that many iterations. I have neer seen such a problem to be honest.
You may also go to:
Render Settings -> Filtering -> Nominal Luminance: set it to 1024
and see if it guides the denoiser better.
You mean the Iray denoiser, rather than DS.
That's right... to be exactly.
OP's issue is very frequently-seen with Post Denoiser turned On ... and this setting won't make any visible difference.
I always use a minimum of 5000 iterations in every render I make, maybe that's the reason I have never seen the problem.
Anyways, You're always more likely to encounter denoiser smudging on very detailed surfaces like wet skin as presented in the pic. Or, if you render with 5000 iterations or more, you can turn the denoiser off completely as it won't do much at this point...