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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 > >
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