Not sure which approach you use, but did you see this? http://www.webkitchen.be/2009/11/13/video-tutorial-elf-yourself-yourself-personalized-video-on-the-web/
Then it's the translation from 2D to 3D space. This is another post by Bartek that I also found relevant for something similar: http://www.everydayflash.com/blog/index.php/2008/07/07/pixel-precision-in-papervision3d/ This will vary a little based on what version of the engine you're using, but I found this thread for Away3D Lite: http://groups.google.com/group/away3d-dev/browse_thread/thread/e356e568b8ca168d/252a0d2f941abdf1?lnk=gst&q=camera+matching#252a0d2f941abdf1 and I know this question has been asked many times. Just search this forum for words like "camera matching" or "2D to 3D" and you you should find what you need. J
