Re: failure of delauny triangulation

• To: Bill Hibbard <billh@xxxxxxxxxxxxx>
• Subject: Re: failure of delauny triangulation
• From: Donna L Gresh <gresh@xxxxxxxxxx>
• Date: Fri, 11 Apr 2003 17:13:46 -0400

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Thanks. It just seems strange, since I've done hundreds of sets of data 
*exactly like this*, that is, with regularly spaced points, even with 
basically the *same* points except for one or two differences here 
(literally one or two differences).

Donna L. Gresh, Ph.D.
Optimization and Mathematical Software Group
IBM T.J. Watson Research Center
(914) 945-2472
http://www.research.ibm.com/people/g/donnagresh
gresh@xxxxxxxxxx






Bill Hibbard <billh@xxxxxxxxxxxxx>
04/11/2003 04:41 PM
 
        To:     Donna L Gresh/Watson/IBM@IBMUS
        cc:     visad-list@xxxxxxxxxxxxx
        Subject:        Re: failure of delauny triangulation


Hi Donna,

Your data include lots of co-linear points, which are undoubtedly
the reason for the failure. You might be able to compute your own
(non-Delaunay) triangulation, say between each pair of adjacent
x-rows, then merge those (then pass the result to DelaunayCustom).
Or perhaps DelaunayClarkson will do better, as Curtis suggests.

Good luck,
Bill
On Fri, 11 Apr 2003, Donna L Gresh wrote:

> I've been using DelaunayWatson( set of two dimensional vertices) quite
> effectively for awhile. However just recently I found a case it's 
failing
> on. The data is not fundamentally different (at least in any way obvious
> to me)  for this failing case, so I'm wondering what's going on. 
Attached
> is the list of x y points.  There are no duplicates. The failure message
> doesn't help too much, just
>
> visad.SetException: Delaunay.finish_triang: error in triangulation!
>
>         at visad.Delaunay.finish_triang(Delaunay.java:592)
>
>         at visad.DelaunayWatson.<init>(DelaunayWatson.java:318)
>
>
>
> Any ideas?
> BTW "jiggling" the points is really not an option for me, as for other
> reasons I need them to be their original values. I'd rather remove
> offending points than change any.
>
>
> Donna L. Gresh, Ph.D.
> Optimization and Mathematical Software Group
> IBM T.J. Watson Research Center
> (914) 945-2472
> http://www.research.ibm.com/people/g/donnagresh
> gresh@xxxxxxxxxx
>



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