Re: [matplotlib-devel] Contour and Vector Plots

[John H. <jdh...@ac...>]

>>>>> "Perry" == Perry Greenfield <pe...@st...> writes:

    >> Hi again,
    >> 
    >> Yes, I had the thought that using C for the algorithm would be
    >> easier as well.  There are actually some very well-written
    >> marching squares contouring algorithms in C already out there.
    >> I will try to find such an implementation and point you to it
    >> or send you the source code.
    >> 
    Perry> Thanks, that would be helpful. In my search I didn't come
    Perry> across many.  Keep in mind the license needs to be
    Perry> compatible with that of matplotlib.

Of course, in addition to the license, there is the patent issue.  I
believe marching squares is patented.  I know marching cubes is.

  http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=4,710,876.WKU.&OS=PN/4,710,876&RS=PN/4,710,876

I checked the header of vtkMarchingSquares.cxx which states

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkMarchingSquares.cxx,v $
 
  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
 
 
     THIS CLASS IS PATENTED UNDER UNITED STATES PATENT NUMBER 4,710,876
     "System and Method for the Display of Surface Structures Contained
     Within the Interior Region of a Solid Body".
     Application of this software for commercial purposes requires
     a license grant from GE. Contact:

but the patent number they reference which is linked above begins with

  A method and apparatus for displaying *three dimensional surface
  images* includes the utilization of a case table for rapid retrieval
  of surface approximation information.

emphasis mine.  So I don't know for sure what the patent status of the
2D algorithm is.

JDH