[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: 3d plotting, griddata and deluanayn
From: 
João Cardoso 
Subject: 
Re: 3d plotting, griddata and deluanayn 
Date: 
Fri, 7 Feb 2003 17:03:02 +0000 
Useragent: 
KMail/1.4.3 
On Friday 07 February 2003 16:20, Paul Kienzle wrote:
 João Cardoso wrote:
 >On Tuesday 04 February 2003 02:28, Paul Kienzle wrote:
 > If you are on Windows, you will need to first figure out how to
 > compile qhull for Windows. We haven't done so yet.

 I should add that under the most recent cygwin and the next mingw,
 there is no reason it shouldn't build and be usable even as a DLL.
 If nothing else, static linking should be possible.

 > If you are on unix, follow the octaveforge/main/geometry/readme
 > instructions
 > for installing qhull. I haven't tried yet with the most recent
 > qhull release.
 >
 > Download the correct version of octaveforge (octave.sf.net) for
 > your particular
 > version of octave (the latest is for octave 2.1.40 I believe 
 > if you are using
 > something more recent, you will need to get the CVS version).
 >
 > ./configure
 > make
 > make install
 >
 > griddata does not work as quickly as I would like. Talk to the
 > qhull author about how to improve it if it is not fast enough for
 > you.
 >
 >I don't think that Qhull is slow, slow is the searching of triangles
 > in tsearch.

 Agreed. Time permitting, I understand the author of qhull is
 interested in having griddata
 functionality in qhull. Please let him know what you are doing.

 >I'm using Sakov's "nn" (natural neighbors) library
 >http://www.marine.csiro.au/~sakov/ that uses Lawson's "walking
 >triangle" algorithm to search for a triangle given a point. "nn"
 > uses "triangle", which not free software, but I have adapted it to
 > work with Qhull.

 Oops  Andreas is using triangle in his FEM stuff. Your are right
  the license is not
 open source since it does not allow redistribution for commercial
 purposes. Does
 triangle do anything that qhull doesn't?
triangle uses exact arithmetic, while Qhull uses floating point; because
of this triangle might be more robust on certain datasets.
triangle does constrained triangulation, which Qhull does not. This is
not required when gridding for plotting.
 >plgriddata() will soon be integrated into PLplot.

 Any chance you could create 'griddata' which we could include in
 octaveforge
 and call that from plgriddata?
It's the other way around, plgriddata() is (will be) a PLplot API, and
the motivation of its writing was to have a griddata.m in
plplot_octave, for plotting purposes.
plgriddata() by itself is mostly selfcontained and with minor
modifications it can be built outside PLplot, but it needs two external
libraries, csa and nn, both written by Sakov, and one of them needs to
be patched to work with Qhull.
But Sakov's libraries have simple programs that exercise the libraries
and can read sample points from data files and write gridded data to
output files, so its easy to embed these programs in an Octave script.
Writing/reading large data files will be slow, though.
Joao

 Thanks in advance,

 Paul Kienzle
 address@hidden




 
 Octave is freely available under the terms of the GNU GPL.

 Octave's home on the web: http://www.octave.org
 How to fund new projects: http://www.octave.org/funding.html
 Subscription information: http://www.octave.org/archive.html
 

Octave is freely available under the terms of the GNU GPL.
Octave's home on the web: http://www.octave.org
How to fund new projects: http://www.octave.org/funding.html
Subscription information: http://www.octave.org/archive.html
