[vtkusers] How to visualize angular velocity of spherical particles?

[Rasmus Hemph]

I am simulating approximately 100 particles wich are moving and
colliding in a 3D box-like domain. I am able to attach a spherical glyph
to each particle point in my field using vtk and tcl, which gives a nice
visualization. 

My problem is that I want to somehow show the angular velocity of the
spheres. The simulations gives me an angular velocity vector omega,
which I map to the particle points, and that gives me an idea of the
rotation. However this is not very intuitive, and it would be much nicer
if I could color half of the sphere in some other color and rotate that
half in the direction of the angular velocity vector in each timestep. 

I have so far created that "half sphere" but have not yet come up with a
good way of rotating that at each timestep in the omega direction
(different omega for all spheres). I would think that somebody has come
across this problem before, and I am hoping for suggestions of some
kind.

On the bottom of http://www.tfd.chalmers.se/~md8hemra/modeling.html 
I have a 2D-movie-version (created in matlab) of what I want to achieve
in 3D.

Thanks in advance.


-- 
Rasmus Hemph

Email:	rasmus.hemph at me.chalmers.se
Tel:	+46-(0)31-772 3589
Address:Thermo and Fluid Dynamics
	Chalmers Universtity of Technology
	S-412 96 Göteborg
	SWEDEN