title: Library for polygon operations
body: <p>I've recently encountered a need for a library or set of libraries to handle operations on 2D polygons.  I need to be able to perform boolean/clipping operations (difference and union) and triangulation.</p>
  
  <p>So far the libraries I've found are <a href="http://code.google.com/p/poly2tri/" rel="noreferrer">poly2tri</a>, <a href="http://www.cgal.org/" rel="noreferrer">CGAL</a>, and <a href="http://www.cs.man.ac.uk/~toby/alan/software/gpc.html" rel="noreferrer">GPC</a>. Poly2tri looks good for triangulation but I'm still left with boolean operations, and I'm unsure about its maturity.</p>
  
  <p>CGAL and GPC are only free if my own project is free.  My particular project isn't commercial, so I'm hesitant to pay or request for any licenses.  But I may want to use my code for a future commercial project, so I'm hesitant about CGAL's open source licenses and GPC's freeware-only restriction.  There doesn't seem to be any polygon clipping libraries with nice BSD-style licenses.</p>
  
  <p>Oh, and C/C++ is preferred.</p>