Freshfromthegrave
06-10-2010, 09:47 AM
Hey guys, I'm having a bit of trouble with interpreting alpha channels of renders coming out of Maya and 3ds Max. It seems that no matter how I render or interpret the alpha channel I'm always left with some kind of border around the render, whether it's white or black or more or less there's always something there. I've rendered out targas and tiffs in straight and premultiplied from my 3d apps (I presume they are premultiplied with black?) and I've imported the footage and interpreted each in all the available options: straight, premult with black and premult with white.
Here's what I'm getting in AE:
Straight Render -> Straight interpret in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481076562943564466
Straight Render -> Premultiplied with white in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075757085306146
Straight Render -> Premultiplied Black in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075758036822642
Premultiplied Render -> Straight in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075752126154498 (this is probably the best option for this particular case, but it varies from render to render depending on the background, and even here there is a slight grey border.)
Premultiplied Render -> Premultiplied White in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075755094763650
Premultiplied Render -> Premultiplied Black in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075748911036994
So I hope you can see those ok, and you'll see I get a border in each possible combination. Premultiplying with a grey of some sorts doesn't help matters much and even if I use a remove matte colour effect it still shows on most renders. I've also tried to use a separate alpha and use it as a track matter but that didn't seem to work either =\ What am I missing here? I think this problem may have been there before and maybe I just didn't notice it. I notice the border is still there with older renders and it does this for renders coming out of max and maya (Vray and mental ray). I read somewhere that some compositing apps don't support premultiplied alphas correctly and that AE does the maths for them wrong or something, is that possible? Does anybody have any advice on how to do alphas right for AE?
Here's what I'm getting in AE:
Straight Render -> Straight interpret in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481076562943564466
Straight Render -> Premultiplied with white in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075757085306146
Straight Render -> Premultiplied Black in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075758036822642
Premultiplied Render -> Straight in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075752126154498 (this is probably the best option for this particular case, but it varies from render to render depending on the background, and even here there is a slight grey border.)
Premultiplied Render -> Premultiplied White in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075755094763650
Premultiplied Render -> Premultiplied Black in AE: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481075748911036994
So I hope you can see those ok, and you'll see I get a border in each possible combination. Premultiplying with a grey of some sorts doesn't help matters much and even if I use a remove matte colour effect it still shows on most renders. I've also tried to use a separate alpha and use it as a track matter but that didn't seem to work either =\ What am I missing here? I think this problem may have been there before and maybe I just didn't notice it. I notice the border is still there with older renders and it does this for renders coming out of max and maya (Vray and mental ray). I read somewhere that some compositing apps don't support premultiplied alphas correctly and that AE does the maths for them wrong or something, is that possible? Does anybody have any advice on how to do alphas right for AE?