[Alex Diestel]

little edit:
the trick with changing the object buffer to the other object actually doesn’t seem to work, i’m still getting white lines.
looks like the only clean way is to get it done cleanly is to use the matte obejct or even better, create the alpha in an extra shot like you would in maya. that means you copy your object, make an entirely black material on everything and an entirely white one on the part where your image belongs.
You’ll have to render it seperately, but it will be clean.

Alex

[Alex Diestel]

Hey Ben.

I seem to have been a little overenthusiastic here.
You are right, the white lining still exists even in linear workflow. I reconstructed your scene and had a go at it.
Still, I found a solution for you. The Object buffers work really well when you have an object in your scene that you want to use solely, meaning you use the white part of you matte as alpha. When you try to use it the other way round, eg “punching a hole in the frame” you use the black part and cinema/afx won’t like it.

solution:
either you have to constuct your object buffers differently, in your case that means put the object buffer on the frame, not the image and then put the frame on top of the image.
or:
use the function “matte obejct” from the compositing tag to “punch a hole” this works just fine, but will directly change your alpha instead of giving you that extra layer. which may not always be disired.

hope this helps.
Alex

[Alex Diestel]

Hey guys.

I have had the very same problem you have now, as has everyone I know using cinema 4D. But I have just now figured the problem out.

I’m so excited. xD

The problem is this: Whem working in cinema you most likely don’t use a completely linear workflow. (check “linear workflow cinema4d” on google for this).
This means that the srgb gamma curve messes up your middle grey values, in this case the semi transparent pixels you get in your alpha channel, leaving you with a brighter or darker rim around your object.

the solution:
turn on linear workflow in cinema, create openEXR files if possible and turn the color management in your after effects on and switch to 32bit color mode if possible. the image you see should be pretty much the same as in cinema.

you now work in a linear workflow and the object channels should now fit your image perfectly.

I hope this was clear. check the numerous tuts on linear workflow out there, it’s a real lifesaver!

Alex