Bill G. wrote: << Wouter suggested http://www.myphysicslab.com/collision.html . That's very nice, but I meant one 3D brick tumbling without collisions in 0g.

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I wrote software (for SGI machines, using GL) to do exactly this in 1987. I might be able to dig it up and it *might* be compatible with OpenGL, but I don't know what the chances are. (Maybe someone else on the list still has a copy of it handy?) Learned a lot about the Jacobi elliptic functions sn, cn, dn in the process, most of which I've forgotten by now. Most interesting thing was to be able to graphically duplicate with real-time computation what happens when one tries to flip a generic rectangular solid through the air 180 degrees about its middle axis. If you aren't familiar with this, I won't spoil your surprise. Go get a typical book, (WLOG size A x B x C with A < B < C), keep it from opening with a strong rubber band, and try to flip it through the air 180 degrees about its B axis. --Dan A.