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This page contains all of the posts and discussion on MemeStreams referencing the following web page: Point in Polygon Strategies: Determining if a point lies within, or outside a polygon. You can find discussions on MemeStreams as you surf the web, even if you aren't a MemeStreams member, using the Threads Bookmarklet.

Point in Polygon Strategies: Determining if a point lies within, or outside a polygon
by Lost at 9:58 pm EDT, Jul 30, 2006

Inside vs. Outside
One definition of whether a point is inside a region is the Jordan Curve Theorem. Essentially, it says that a point is inside a polygon if, for any ray from this point, there is an odd number of crossings of the ray with the polygon's edges (Figure 1). This definition means that some areas which are enclosed by a polygon are not considered inside. The center pentagonal area inside a star is classified as outside because any ray from this area will always intersect an even number of edges.


 
 
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