Hi Brian,
The following command creates an image file of the current screen:
viz.screencapture(filename)
It would be up to you to create a movie with these images. Also, if you plan on making a long movie, then this might not be the best way to go about this. There are some programs out there that will automatically create a movie for you. I just found this one and tested it out and it looks pretty good.
http://www.fraps.com/
Good luck!
-- farshid