You can build a movie from a gravit sumulation using screenshot
sequences. I have put my experiences into a small how-to on github:
http://github.com/FrMo/gravit/wiki/How-to-create-movies
best wishes,
Frank.
btw, the next gravit release still has a chance to appear before
christmas :)
(... yes, we know that the windows build environment needs some
cleanup and a new how-to....)