Polygon in or out?

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2 total messages Started by Ed Deeters Tue, 25 Aug 1992 19:52

#331

Author: Ed Deeters
Date: Tue, 25 Aug 1992 19:52

8 lines
571 bytes

Hi, does anyone know a fast way to determine if a point(x,y) is inside or outside
of a polygon when the polygon is defined by n points(x,y) given in a clockwise manner?

thanks for any help 

Bill Deeters
elvis@sioux.ee.ufl.edu

Re: Polygon in or out?

#348

Author: Patrick Tibbits
Date: Wed, 26 Aug 1992 18:55

6 lines
734 bytes

Define vector ai from vertex i to the point p under consideration.
Define vector bi from vertex i to vertex i+1.
Then ai cross bi must be postitive for all i for p to lie within the polygon.


Patrick

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