The approach I would try in AE would be using Trapcode’s Particular. You would make two layers of particular. The first would be for the large particles, the second for the small. Make the layer of large particles use the physics model “bounce”. Then adjust the setting so the particles stick to the filter layer ( which would be a 3D layer). The smaller particles should use the physics model “air”. I would use a displacement field that mimics the motion of the filter, so when it passes through the small particles they look like they are being disturbed by the filter. It’s a little complicated, but i think it could work.
As for collision detection, in particular the particles can collide with a layer (in the “bounce” mode), but not with each other. I don’t think any of the AE particle generators can do that.
Matt Hall
Director, Digital Post
CCG MetaMedia, Inc.