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Denoising produces black pixels around specular bright areas

3 REPLIES 3
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Message 1 of 4
daniel2SH2D
184 Views, 3 Replies

Denoising produces black pixels around specular bright areas

Hello!

After rendering an animation sequence, denoising the renders with anything but the gentlest almost invisible settings using the Noice denoiser results in what look like black NaNs / black pixels around specular highlights.

I've set the log to 'debug' and there are no warnings other than that I'm calculting a lot of rays and might want to lower some sample settings!

Any idea or experience with the denoiser getting freaked out by, say, the Arnold physical sky? Or why am I getting black pixels when denoising?

Many thanks

Daniel

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Message 2 of 4
thiago.ize
in reply to: daniel2SH2D

I'm not sure why that could be happening. A guess is that maybe the image you're trying to denoise has infinite or near infinite values, which is more likely if this is a 16-bit float (half float) exr? You can use the oiiotool that comes with arnold to see if the values are really high. You run it from the command line using: oiiotool --stats your_image.exr
Here's what it looks like for me with a good image, which shows no nans, infs, and the largest value is 17.171875:

$ arnold/bin/oiiotool --stats Hall.exr

Hall.exr : 3584 x 1792, 3 channel, half openexr
Stats Min: 0.001424 0.000858 0.000474 (float)
Stats Max: 13.546875 16.046875 17.171875 (float)
Stats Avg: 0.283467 0.193333 0.125732 (float)
Stats StdDev: 0.400484 0.388182 0.351394 (float)
Stats NanCount: 0 0 0
Stats InfCount: 0 0 0
Stats FiniteCount: 6422528 6422528 6422528
Constant: No


Message 3 of 4
maxtarpini
in reply to: thiago.ize

You ain't sure why that _could_ happen ? Jeez, must be a 'senior moment' 🙂

Hint : geometry against the 6EV white background is really difficult to render.. with or without a denoiser.. dark pixel blocks are denoiser artifacts, jagged edges are a filtering artifact... as you see they both happens only against the super bright background.

screenshot-from-2021-08-04-21-32-02.png

Message 4 of 4
maxtarpini
in reply to: daniel2SH2D

Reduce the denoiser window so the denoiser won't have to filter against high freq spikes and low freq stuff.

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