Re: Volume rendering of Irregular3DSet

Hi Gunnar,

> > VisAD does not provide a method for computing boundaries, so
> > you'll have to write one. You'd put the boundary triangles in
> > an Irregular3DSet with manifold dimension = 2 rather than an
> > Irregular2DSet. Finding them could be tricky. Perhaps Curtis
> > has someting to add.
> After some finger twidling, I managed to get the 2D version of boundry
> extraction up and running. First I located the neighbors for all nodes,
> then located the ones that didn't have a complete neighbor list,, which
> means the element is on the boundry, then locate its boundry edges. Should
> only add a few loops and it will work for 3D as well. I could post the code
> if anybody is interrested.

Good. If you put your code on a server we will add a link from
the VisAD web page.

> The reason I'm still posting is becaus I'm wondering how to represent the
> line segments I extract from the 2D boundry. 3D triangles are represented
> with DelaunayCustom. I'm using a Gridded2DSet, simply appending all the
> points in the order they were found. Luckily the data is ordered in the
> sourcefile such that the connected points surround the area in a nice
> fashion, but I'm not comfertable with the solution. Can I represent the
> linesegments as line segments in a Set so I still can define field values
> over them?

The current VisAD Field implementations attach values to
points rather than lines (or polygons or polyhedra). It
would be possible but a lot of work to define new extensions
of Function for values attached to line segments.

However, you could easily generate an appropriate type
of Set for your line segments and attach values to the
end points of the line segments. You might use a UnionSet
of Gridded2DSets with manifold dimension = 1, as we do for
map outlines (see visad/examples/ for a simple
example). For lines in 3-D you can use a UnionSet of
Gridded3DSets with manifold dimension = 1, and for triangles
in 3-D an Irregular3DSet with manifold dimension = 2.

Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

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