A basic example of collision detection in 3D, where moving particles bounce off a static terrain.
[By the way, my apologies for the cobwebs that have accumulated on this site; I’ve been busy over the past few months dealing with moving back to the Bay Area from Detroit :) ]
A couple things on it which could be of use …
From: http://www.zeropointnine.com/blog/collision-detection-between-particles-and-polygons
