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Old 09-30-2009, 04:54 AM   #1
sean3dmonkey
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black pixels in my render

I'm using mental ray with production quality and I get several black pixels in my render. Is there a check box i forgot to check?

I have attached an image.

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File Type: jpg black pixels.jpg (43.2 KB, 62 views)
 
Old 09-30-2009, 06:03 AM   #2
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Strange. Rendering as .exr? I got black spots with the T2S shader rendering out 32bit floats. Turned out the values in those areas were too high for the shader to handle. Could be something similar.
 
Old 09-30-2009, 08:19 AM   #3
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Yup those are NaNs or +/-inf values. The little squares that you see will be the same size as your filter width, since the bad values generated will propogate to all pixels touched by the filter.

They're basically the result of bad shader code - either a divide by zero or an overflow. Short of diving into the code and trying to debug it, you might have some luck trying different values for your lights and shaders and hope you don't trip whatever bug is causing that.
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Old 09-30-2009, 10:26 AM   #4
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You could also try using this shader DL3DBlackspotsRemover :
http://www.dl3d.com/index.php/telec...de-shaders.html
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Old 09-30-2009, 04:25 PM   #5
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hmm. don't know much about the shader bug stuff. I'll try painting them out in the render.

thanks for the help fellas.


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Old 09-30-2009, 04:35 PM   #6
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Come to think of it. The pixels are not on the object with the shader. The black pixels are on the light rays, the lights don't have a shader on it. Could there be a check mark box in a render tab or a light tab that I need to check or uncheck?

Sean
 
Old 09-30-2009, 04:42 PM   #7
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Sorry I don't know enough about mental ray to know precisely what's going on, but there'll likely be a volume shader somewhere that's running to create the light beams effect. Tweaking the volumetric settings might help.

Whatever you do file a bug report with autodesk or mi
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Old 09-30-2009, 05:09 PM   #8
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Quote:
Originally Posted by lazzhar
You could also try using this shader DL3DBlackspotsRemover :
http://www.dl3d.com/index.php/telec...de-shaders.html


Possibly one of the most useless things I've downloaded. For me, at least. Unless they're very small or on an area of no detail, its still gonna be work to remove them in post. May as well figure out why that's happening to begin with.
 
Old 09-30-2009, 07:03 PM   #9
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Quote:
Originally Posted by phix314
Possibly one of the most useless things I've downloaded....

You did? I never downloaded this as far as I remember because I never got those black spots.
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Old 09-30-2009, 08:01 PM   #10
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Cool, where would find this volume shader?

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Old 09-30-2009, 08:12 PM   #11
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Cool, so the black pixels went away when I broke the connection of the noise map tot eh Fog spread. I just gotta find a map to plug back in that doesn't give me black pixels.

Sean
 
Old 09-30-2009, 08:59 PM   #12
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If that was the problem it's possible you were using a 2D procedural when a 3D was needed or vice versa =)
 
Old 10-01-2009, 12:02 AM   #13
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Quote:
Originally Posted by lazzhar
You did? I never downloaded this as far as I remember because I never got those black spots.


Yea like I mentioned the T2S shader had some of that when it was used for glass coating, the blackspot remover simply "spot tones" those little fellers. Not very useful when there's a fair amount of detail around em.
 
Old 10-01-2009, 12:55 AM   #14
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Cool, thanks for all your help, guys.
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Old 10-04-2009, 01:46 PM   #15
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Another thing that could create black spots is shown in this example. It's showing some cracks on a nurbs sphere but I tryed wich polygons and subdvs and it has this problem as well.
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