Opposite of AO possible?

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Old 02 February 2013   #1
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 February 2013   #2
Hi interactiveBoy,

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

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Old 02 February 2013   #3
Inverted AO pass in post?
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Old 02 February 2013   #4
I have loaded AO into the luminance channel to get a contact glow.
 
Old 02 February 2013   #5
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 February 2013   #6
try to invert all normals of your polygon object.
Maybe this helps....
 
Old 02 February 2013   #7
Doesn't just Inverting the Knots on your AO Gradient already do this ?
 
Old 02 February 2013   #8
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..

Lee
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Old 02 February 2013   #9
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 February 2013   #10
this is with the grunge shade. is this the effect you are looking for?
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Old 02 February 2013   #11
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 February 2013   #12
Did you try proximal shader in edge mode?
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Old 02 February 2013   #13
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