To the best of my knowledge, it was animated in Maya and rendered with Pixar's Renderman. When I was in that group, we used IDL to do any elaborate calculations

To the best of my knowledge, it was animated in Maya and rendered with Pixar's Renderman. When I was in that group, we used IDL to do any elaborate calculations needed, and then imported the data into Maya/Renderman. This is exactly what Hollywood does when they have to render a scene that requires a lot of simulation. I can ask Ernie if he used anything special for this production.