I render Poser figures in Cinema 4D, but I think you can do the same in Poser: what I generally do is render the animation (as stills with an alpha channel, then assembled in Quicktime pro) with the background movie playing in the background, then composite in Final Cut, that way you don't have to worry about antialiasing to the wrong color and getting that weird edge. If the background movie doesn't change a lot, you can sometimes get away with using a still in the background.

--Tim

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