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Getting a Straight alpha from Ambient pass
I have molecular objects that use the cheen shader. When The passes are split out, the cheen is using the ambient pass and not rendering as a diffuse pass. Well I also rendered the molecules as object ID to get a matte (because other objects are all around them). The problem is, if I do a normal render, The ambient pass will not cut out where the other objects are, so I use the Object ID pass as a luma matte in AE to knock out where the other objects should be. However since the object ID matte and the ambient pass are both anti-aliased, When one mattes the other, I get black fringing around the edges. I tried turning everything off but the molecules and turning off anti-aliasing to get a pass with full edges that I could use the ObjectID pass to matte it out. However when I do this, It looks terrible, the Object ID pass barely cuts into the edges of the rgb pass so you still see the jaggies.
I tried doing a Stright alpha pass. This only worked for the diffuse pass and not the ambient pass.
Chris Smith
https://www.sugarfilmproduction.com -
1 Reply
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Well I did a Straight Alpha pass and just rendered out normal (not as multipass) and turned everything off but the objects I wanted. In AE I had it ignore it’s own alpha channel. Then I used the object ID as a luma matte. This worked. However, I guess now my question is: Is this the normal/most efficient way to do this?
Whenever an Object ID matte is created, is the normal workflow to always render out the rgb images as straight alpha, then override this alpha in the compositor? Or are ppl living with the double anti-aliasing creating fringes?
Chris Smith
https://www.sugarfilmproduction.com
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