Geometry Boost List: [ggl] Re: Problems with the difference between two polygons

Subject: [ggl] Re: Problems with the difference between two polygons
From: Barend Gehrels (barend)
Date: 2011-08-05 06:27:37

> Gtl outputs a list vertex equal to the first vertex.  GTL also retains colinear vertices.  If you discard colinear vertices or don't output the redundant last vertex then your vertex count would come out lower than mine.  I'm not sure if GGL outputs colinear vertices, but if not that could explain the two vertex difference between Barend's implementation and my own.

GGL does indeed output colinear vertices, if they are in the input 
polygons, or happen to be an intersection point.

Another source of difference in number of vertices might be the closure.

Regards, Barend