Hi Analog-x, Sounds like a couple of things are going on. First, the spherical particles bounce from their hotpoint (the center) and not their perimeter. So, if there is not enough sideways motion, the particle will stop on the plane with half showing above it and half showing below it. Secondly, you may want to create a gentle slope to your plane so all particles roll off. You can do this by rotating the plane by 1 degree or so, or, create a custom plane in the Vertex Modeler that slopes very gently in four directions. Post back with any questions. Hope this helps. Welcome to Carrara. Mark