Hello,
Thanks for your response Bill. I think I got some ideas, but still have a
few questions:
1) It doesn't appear that I can simply create the surface:
Irregular3DSet(xyz, samples,null, null,null, new DelaunayClarkson(samples));
I was thinking if there are some methods within DelaunayClarkson where I
can obtain the proper samples and tri and simply feed them to the
DelaunayCustom. For example something like the following:
DelaunayClarkson test = new DelaunayClarkson(samples);
set = new Irregular3DSet(xyz, samples,null, null,null, new
DelaunayCustom(test.getSamples?,test.getTri?));
2) If there aren't any methods as mentioned in (1), I would imagine that I
will need to determine which data points form the convex hull based on the
Walk[i][j] and then feed those data to DelaunayCustom. While I know the
order of the data set (samples) that is going into
DelaunayClarkson(samples), how do I know their orders within
Walk[i][j]? In other words, which points within samples triangular face j
is composed of?
Like always, thanks very much,
john
At 11:12 AM 8/26/2002 -0500, you wrote:
Date: Sun, 25 Aug 2002 17:03:37 -0500 (CDT)
From: Bill Hibbard <billh@xxxxxxxxxxxxx>
To: John Yao <johnyao@xxxxxxxx>
cc: visad-list@xxxxxxxxxxxxx, qingwei Fu <qfu@xxxxxxxx>
Subject: Re: convex hull
Hi John,
The Watson and Clarkson algorithms included in VisAD for
finding Delaunay triangulations were also used by their
authors to find convex hulls.
I have never tried it, but you could probably apply either
visad/DelaunayWatson.java or visad/DelaunayClarkson.java
to find a tetrahedralization of your 3-D samples, then
look at its 'int[][] Walk' array to find faces that have
no adjacent tetrahedron. These faces should form the
convex hull of your data. Specifically, if Walk[i][j] = -1,
then triangular face j of tetrahedron i is part of the
convex hull.
Note this is just a theory off the top of my head, and
one that I have never tried. If anyone can correct me,
please do.
Cheers,
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
On Sun, 25 Aug 2002, John Yao wrote:
> Hello,
>
> I have generated some shapes using (DelaunayCustom(samples,tri)) from the
> Irregular3DSet. However, the resulting geometry (surface covering)
did not
> turn out the way we want it to be. We are investigating a different
> algorithm called "convex hull"
> (http://www.cse.unsw.edu.au/~lambert/java/3d/hull.html) to generate the
> surface based on the computed data points.
>
> I am just curious to know if VisAD happens to support this algorithm or
> method of creating the surface cover. Thanks very much.
>
> john
>
>
