I'm releasing the ElastoLab physics as open source and I've ported it to 
Squeak.  If you'd like to try it, visit:

    http://www.simberon.com/Services/SmalltalkSoftware/

The classes in SimulatedPhysics.st offer basic physics simulation of 
particles, gravity, air resistance, springs and elastics.  This code is 
fairly clean and works quite well.  The code in 
SimulatedPhysicsAdvanced.st covers barriers and rods which are much more 
computationally difficult and contain some messy code and algorithms.  
The code in SimulatedPhysicsTestcases.st provides testcases for some 
things in the SimulatedPhysics.st package but doesn't yet test the 
advanced code.  At this time, there is no additional documentation.  I'd 
suggest just looking at the testcases and trying things from there.

There's no GUI with this code.  I'd like to see what other people can do 
with it.  The SimulatedPhysics part should be fairly easy to convert to 
3D if you wish.  The Advanced part is much more difficult to make 3D 
because of rods need a tensor matrix instead of just a number for the 
moment of inertia and because of barriers which require a 3D plane model 
instead of just a line.

If you'd like to see what this physics code is capable of doing, check 
out ElastoLab at:
     http://www.simberon.com/home.htm

I'd like advice from the Squeak community on license options.  I could 
use the Squeak license (although its references to Apple seem strange in 
this context).  What do other people do?

Anyway, for now, the code is there and you can play with it.  If you 
have any improvements or enhancements, e-mail them to me and I'll put 
them up on the site.

Have fun - that's what it's all about.

David Buck
Simberon Inc.
www.simberon.com