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Alpha Channel for a transparent object
Hi,
I have a video window that I’ve built in C4D….I am adding the video in Post in AE, by rendering a MP render, and using an object buffer, to render an alpha channel for the area where my video will go….Here’s the problem. I want the image where the video goes to be transparent (like a pane of glass) so I can dial in the transparency of my video in post. When I turn off the object, or make it transparent, I don’t get an image in my object buffer. This makes sense, but I’m trying to avoid 2 renders (since they’re pretty long) one with the pane off or transparent, and one with it on so I can get an image buffer for that pane. Is there an easy way to do this in one render? I’ve tried turning off “seen by camera” in the compositing tag, but then I don’t get an image in the image buffer?Mike
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1 Reply
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I may be misunderstanding you, but you cannot avoid doing two renders. I don’t see why this should be a problem, though, as effectively the second render only would have to contain the matte for the plane and will render very fast. You just need to turn your scene into a b/w version using eitehr the matte object color in the compositing tag or by adjusting your materials. In the beauty pass make your plane black so it only contains specular highlights and reflections. Using your matte you can isolate those reflections and highlights and use them e.g with Overlay mode on your replacement footage.
Mylenium
[Pour Myl
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