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NAN issues with OpenEXR

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Vance Bowman

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NAN issues with OpenEXR

PostWed Feb 03, 2016 2:54 pm

I've rendered a bunch of frames from Modo, but when I bring them into Fusion there are little black squares (NANs) in random places on random frames. I've heard this can be a problem with OpenEXR files. How do you guys normally deal with this?
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Chad Capeland

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Re: NAN issues with OpenEXR

PostWed Feb 03, 2016 4:03 pm

If you just have one or two, paint them out. If you get it regularly, you'll be well served with a Fuse or Custom Tool that handles it. With a Fuse, you can directly test if it's a NAN pixel, with a CT I think you have to test that it is a number, like test if the absolute value of the pixel is great than or equal to zero. Then for those pixels fill in with an average or median of the surrounding pixels.

File a report with Modo. Chances are they aren't handling things like divide by zero in some part of their shading or rendering.
Chad Capeland
Indicated, LLC
www.floweffects.com
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Vance Bowman

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Re: NAN issues with OpenEXR

PostWed Feb 03, 2016 4:07 pm

Thanks Chad.

I forgot to mention that when I open the same frame in Photoshop the black pixel isn't there.

I will file it with the Foundry.

Do you know of a Fuse that does this?
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Chad Capeland

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Re: NAN issues with OpenEXR

PostWed Feb 03, 2016 5:52 pm

Vance Bowman wrote:Do you know of a Fuse that does this?


I wrote a Fuse and Cg ViewShader for another project (VrayRT based), but I can't find them right now. :cry:

I know it didn't take more than about an hour to do both, so I know they were pretty simple. The ViewShader was used to flag the pixels (in bright magenta) so you knew which clips/frames to run the Fuse on.
Chad Capeland
Indicated, LLC
www.floweffects.com
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Vance Bowman

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Re: NAN issues with OpenEXR

PostThu Feb 04, 2016 2:47 pm

So what do you do if you can't paint them out? The paint tool isn't working for me. When I try to clone it out, it won't paint anything in that black square. Even if I try to simply paint it another color it won't paint anything in the black square. It will paint/clone every pixel around it, but not inside it. This is strange. It doesn't show up at all in PS, but in AE and Fusion they are there.
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daniel.koch

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Re: NAN issues with OpenEXR

PostMon Sep 14, 2020 3:35 am

Late, but for future reference:

Try the Stamp apply mode. The bad pixel needs to be replaced outright. Anything with transparency or softness will try to blend with the invalid values, which is mathematically illegal and will only produce more bad pixels.
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Pieter Van Houte

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Re: NAN issues with OpenEXR

PostSun Sep 20, 2020 7:24 am


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