This is an example of extending the "Particles" example in Tutorials 3 
and 4 to 3D.

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 time).  There's not enough memory in the
default Java to handle Java3D's ridiculous memory requirements.  You'll
need to increase the Java heap like so: 

	java -Xmx200m sim.app.particles3d.Particles3DWithUI

Likewise, applets won't be able to run this example.  The building of all
these shapes is also what causes the very long pause at the beginning of
the run, and the "unbuilding" is what causes the even LONGER pause at the
end of the run.  It's not something we can get around -- it's just a flaw
in Java3D.  We're working on a better approach for 3D value grids. 
