Re: Shapes in space

• To: David Nguyen <dave@xxxxxxxxxxxxxx>
• Subject: Re: Shapes in space
• From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Date: Mon, 18 Feb 2002 01:34:57 -0600

Hi David,

> I have a small VisAD program that will plot particles in space like
> this:
> 
> (index) --> ( x, y, z, value )
> 
> I run my data files through a cluster algrothm and have textual
> information concerning the clusters, but I would like to emphasize these
> clusters in the visualization. I think I would like to draw boundaries
> around these cluster and was wondering if there is a method in VisAD
> that will allow me to accomplish this?

VisAD allows you to define closed surfaces (for a 3-D
boundary) as an Irregular3DSet with manifold dimension
= 2, but does not provide any method for computing that
boundary. Your own cluster analysis code would need to
do that.

> P.S. any other suggestions on how I could visualize my clustering
> results would be appreciated.

You might assign an integer cluster_index to the points in
each cluster, then produce data with MathType:

  (index -> (x, y, z, value, cluster_index))

You can then display with a ScalarMap cluster_index -> RGB
so the points in each color have a distinct color. You may
also use a ScalarMap cluster_index -> SelectRange so that
you can interactively select the points in a single cluster
or a range of cluster_index values. If you reorganize your
data as:

  (cluster_index -> (index -> (x, y, z, value)))

Then you can display with a ScalarMap cluster_index -> SelectValue
which will allow you to select single clusters with very fast
response.

Good luck,
Bill
---------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • Shapes in space
    • From: David Nguyen