In this movie, we chose to use 12 generators, but we fixed 5 of them, allowing the other 7 to move as usual. The generators were positioned at random. Over 100 iterations, you can see the free cells adjusting themselves. The fact that 5 of the cells are fixed can be detected by the way that some cells have generators (gray dots) that do not converge to their centroids (the black dots).
We saved a PPMB file containing an image of each step, converted these to JPEG files with consecutive file names, fed that into QuickTime Pro to create an animation, and saved the result as an MPEG-4 file.