These planets are roughly the same size and colliding fairly slowly (in terms of planet speed) correct? If so sorry to burst everyone's bubble but, if planets of roughly equal size just kind of drift into each other they would not simply 'smack' into each other. Their electromagnetic fields would tear them apart, which would result in a new 'composite' planet forming. But at such unstable stages in their development the resulting planet would be unknown to be 'composite.' But wait! In the eyes of physics your planets can still be like that! If the planets have either, low density, non-iron, or forming planetary cores. Sorry for the long, confusing, possibly unneeded post, but, I guess what I'm trying to say is, add tidal bulging to the planets and make them more active according to that. I'm sure nobody would notice or even thought of that but, for the sake of realism you might want to look into that. Also it's still a little short, other than that great render.