I’ve been experimenting with nParticles in Maya to try to simulate a crowded cellular environment with Brownian motion and collisions. The molecules can be seen to appear and disappear sometimes. This is because the part of the simulation closest to the camera is invisible, so that we can see the interior of the simulation, which will include collisions from every direction, rather than creating a force field that molecules will bounce off. So when molecules pass the threshold, they become hidden or visible. I’m (and we as a group are) still considering different ways of creating and simulating these kinds of environments.