RE: Bug resampling field with Irregular2DSet to Linear2DSet

  • To: "Bill Hibbard" <billh@xxxxxxxxxxxxx>
  • Subject: RE: Bug resampling field with Irregular2DSet to Linear2DSet
  • From: "Ian Graham" <ian@xxxxxxxxxx>
  • Date: Tue, 29 Apr 2003 19:53:12 -0600
Thanks Bill, it works!

As for my data being weird, well<grin>, it doesn't seem it to me!  It
consists of measurements that are taken over as close to a perfect grid as
possible, but likely rotated and certainly with many gaps and offsets due to
physical obstructions in the field.  As for the larger sizes, I was enjoying
Curtis's DelaunayFast until I started getting triangulation errors.

I worry when you mention that co-linear points cause problems, because
almost all of my data is similarly co-linear, although often not orthogonal
to the axes.  That invites my implementing my  own triangulation and using a
CustomDelaunay that exploits this co-linear tendency, but that doesn't seem
trivial even in my near-gridded cases, and I still have to support the
general case.  I was hoping that in the medium-term I could use well-known
algorithms _that_work_ even if they're imperfect:  I'm not terribly fussy
how equilateral my triangles are, but I do care that the coverage is
complete and non-overlapping so that interpolation can work.  Can none of
the Delaunay algorithms guarantee this?

And Curtis, thanks for the DelaunayFast.  Unfortunately, I'm getting a fair
number of "Delaunay.finish_triang:  error in triangulation!" exceptions.
But fortunately it's fast enough that I can always try it first!

My apologies for the large attachment, I just never succeeded in reproducing
the problem with a smaller dataset.  It's just as well that it didn't make
it to the list.  I guess I should've written the data in binary form instead
of ascii.

Thanks again for your help!