How to check if the polygon is not intersected itself?

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I want to check if the polygon is not intersected itself, how to do this with C++ or C#? Thanks.

Posted 22-Feb-14 4:42am

Andrewpeter

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agent_kruger 22-Feb-14 10:44am

what have you tried so far? and the code to create the polygon?

Andrewpeter 22-Feb-14 10:53am

I created the polygon with n points given (x1, y1),...,(xn, yn). I dont know any algorithm to check if the polygon is intersected or not intersected itself.

agent_kruger 22-Feb-14 13:24pm

is the polygon side specific in number?

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OriginalGriff · Accepted Answer · 2014-02-22T05:29:00

If you mean "how do I detect a self-intersecting polygon?" such as an hourglass:

X------>X
 ^     /
  \   /
   \ /  
    \
   / \
  /   \
 v     \
X------>X

Then it's non-trivial. But...several algorithms exist, including Bentley-Ottmann which is described here: http://geomalgorithms.com/a09-_intersect-3.html[^]

You may be able to find a suitable C++ or C# implementation via Google - I haven't looked - but it might be easier to write your own, the pseudocode examples look reasonably simple to follow.

[edit]Drew arrow head on wrong end... :doh: [/edit]