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Re: some geometry questions. [message #48170 is a reply to message #48152]

Wed, 29 March 2006 21:29

Karl[1]
Messages: 79
Registered: October 2005

Member

You might do a google search for "signed areas" and/or see:

http://softsurfer.com/Archive/algorithm_0101/algorithm_0101. htm#Triangles

The idea is to take the vector cross product of something like
(v4-v1)x(v2-v1) and compare it to (v2-v3)x(v4-v3). If the signs of the
z components are different, the lines cross.

A much bigger hammer to use is IDLgrTessellator. If you call the
AddPolygon method with those 4 points and then call the Tessellate
method, the tessellator will always return 2 triangles, but it will
return a 5th point if the lines cross, since the 5th point is needed to
define the point of intersection.

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[Message index]

		Re: some geometry questions. By: Craig Markwardt on Fri, 31 March 2006 08:50
		Re: some geometry questions. By: Karl[1] on Wed, 29 March 2006 21:29
		Re: some geometry questions. By: David Fanning on Wed, 29 March 2006 15:56

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