From: nagle@netcom.com (John Nagle)
Subject: Re: Point in Polygon routine needed
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
Lines: 18

Andrew Lewis Tepper <at15+@andrew.cmu.edu> writes:
>I don't know if this routine is "standard", I just came up with it recently:
>For a polygon of points p1...pn, and a point P, make a table as follows:
>T(1)= angle from p1 to P to p2
>T(2)= angle from p2 to P to p3
>...
>T(n)= angle from pn to P to p1
>express all angles as: -PI < angle < PI.
>Add all entries in the table. If the sum = 0, the point is outside. If
>the sum is +/- PI, the point is inside. If the point is +/- xPI, you
>have a strange polygon. If ANY angle was = +/-PI, the point is on the
>border.

     I think it's known, but it's neat.

     Can it be extended to 3D?

						John Nagle