The physics continued into the afternoon with a session on continuous collisions, which presented a variety of methods for solving collisions (or approximately solving collisions to within a certain threshold) without allowing penetration. This was a pretty interesting session, but the highlight of the afternoon was a session from NVidia which presented methods for iteratively solving contacts between rigid bodies without any distracting jitter. Stacking objects is difficult, and the reason it is difficult is because there are a whole bunch of forces that all rely on each other being in balance together, at the same time. This is hard to do in a computer because you generally have to calculate impulses one at a time, without knowledge of other impulses that you haven’t calculated yet, but that will affect the impulse you’re calculating at the moment. Often, the result is jitter, which is when objects in a pile constants jump and jitter around rather than coming to rest in a stable pile. Two techniques we presented. One was better suited to single cores and one was capable of being parallelized on the GPU. They were both pretty complex so I’m not even going to try to explain them here, but the results were pretty impressive. The technique presented is being used in Hawken, which is a free to play first person mech fighting game. Check it out at