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Old 02-19-2013, 08:10 PM   #1
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Opposite of AO possible?

Been racking my brain trying to come up with a procedural shader method that will work the opposite of Ambient Occlusion.

AO typically looks at polygonal angles that are less than 180. I want to shade things based on polygonal angles greater than 180.

So instead of the shader creating dark shadows in corners, I want it to highlight edges and fade off toward the middle of the polygon.

Thoughts?
 
Old 02-19-2013, 08:22 PM   #2
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Hi interactiveBoy,

I'm likely way off here,
but I thought of using the Fresnel shader maybe?

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Old 02-19-2013, 08:23 PM   #3
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Inverted AO pass in post?
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Old 02-19-2013, 08:25 PM   #4
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I have loaded AO into the luminance channel to get a contact glow.
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Old 02-19-2013, 08:27 PM   #5
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This thread may be helpful. http://forums.cgsociety.org/showthread.php?t=1062836
AoB surface shader. Much faster to calculate than AO and one of the best shaders around imho.
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Old 02-20-2013, 02:17 AM   #6
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try to invert all normals of your polygon object.
Maybe this helps....
 
Old 02-20-2013, 03:13 AM   #7
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Doesn't just Inverting the Knots on your AO Gradient already do this ?
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Old 02-20-2013, 08:15 AM   #8
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Quote:
Originally Posted by interactiveBoy
Been racking my brain trying to come up with a procedural shader method that will work the opposite of Ambient Occlusion.

AO typically looks at polygonal angles that are less than 180. I want to shade things based on polygonal angles greater than 180.

So instead of the shader creating dark shadows in corners, I want it to highlight edges and fade off toward the middle of the polygon.

Thoughts?



I thought AO was a proximity thing not angle based..

The grunge shader from Paul Everett has some settings to do this kind of thing..

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Old 02-20-2013, 04:36 PM   #9
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Quote:
Originally Posted by leed
I thought AO was a proximity thing not angle based..


When an object surface has an angle less than 180, one poly will have a proximity to the other poly.
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Old 02-20-2013, 04:58 PM   #10
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this is with the grunge shade. is this the effect you are looking for?
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Old 02-21-2013, 06:17 AM   #11
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What's the difference between Paul Everett's Grunge shader and the AoB shader. I'm a Mac user and AoB isn't available but it looks really interesting if it's faster than traditional AO.

Can't you use the AO in a layer as a mask for a white colour. It would be slow but I am pretty sure that would work. Having said that inverting the knots should do the same shouldn't it
 
Old 02-21-2013, 10:02 AM   #12
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Did you try proximal shader in edge mode?
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Old 02-21-2013, 10:02 AM   #13
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