Hi Brian,

The physical interaction of particles is different than other shapes in your scene when working with collisions. Carrara will correctly "bump" objects into one another for everything EXCEPT particles.

Particles are instantiated - that is, ghosts of the source object and are kept track of only by the hot point and nothing else. So, when particles collide with objects, all Carrara is tracking is the hot point, not the geometry. This results in the visible particles penetrating other objects in the scene up until the hot point collides with another object.

Mark