Here’s a test I did with green screen, I used Blender to make the matte. I didn’t finish it completely, whenever I’m jumping over the edge there is some see through. The compositor didn’t like me attempting to fix it.
Here’s the video on youtube: http://www.youtube.com/watch?v=fei5L4M8A7o&list=UUynXq0lPbDL3qQOI1O2mo0g&index=2&feature=plcp
There’s an annotation on the video giving the link to the original green screen shot.