This application is an early example of the ValueGrid3DPortrayal. 
Unfortunately, Java3D gets quite slow and memory hungry when drawing large
numbers of shapes (there are over 27,000 in this example in the worst case --
but most are invisible at any tiem.  The building of all these shapes is what
causes the very long pause at the beginning of the run.  Also, you'll need
to increase Java's heap in order to handle the model.  Something like
	java -Xmx200m sim.app.particles3d.Particles3DWithUI
...will do the trick.

