Path: utzoo!utgpu!news-server.csri.toronto.edu!csri.toronto.edu!corkum
Newsgroups: comp.graphics
From: corkum@csri.toronto.edu (Brent Thomas Corkum)
Subject: Re: Point in Polygon Problem
Message-ID: <1990Aug23.181401.2258@jarvis.csri.toronto.edu>
Organization: Civil Engineering, University of Toronto
References: <5990@milton.u.washington.edu> <1990Aug22.022743.4139@twinsun.com> <2018@idunno.Princeton.EDU> <1990Aug23.000651.10581@twinsun.com> <2034@idunno.Princeton.EDU> <1990Aug23.174650.3592@odin.corp.sgi.com>
Distribution: comp.graphics
Date: 23 Aug 90 22:14:02 GMT
Lines: 21


There's one question I have concerning this algorithm that I hope someone
can answer. It seems to me that a point exactly on an edge can evaluate
either inside or outside depending on which edge your on.

ie.

        +----A----+
        |         |
        |         |
        +----B----+


Using the algorithm I've seen, A would evaluate inside and B outside. Is
there a quick and dirty way to handle points exactly on edges? I realize
that a seperate calculation can be done to determine whether a point
is on a line but this is expensive computationally isn't it?

Brent
corkum@ecf.toronto.edu