Keren's blog

Winding number algorithm
By Keren, 12 years ago, In English

I learnt Ray casting algorithm.I found on net. But I can't understand Winding number algorithm. Please somebody explain this algorithm or give example code(C or C++).

Thank you for everthing.

I'm so sorry for language mistakes

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12 years ago, hide # |
 
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Dear kerem, please clearly explain what do you mean with Ray casting or Winding number. I dont remember such thing from last year. What problem do you use them for ?

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    12 years ago, hide # ^ |
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    Ray casting algorithm is a method to determine whether a point lies inside a simple polygon or not. The method is to cast a ray from the point in some direction and count the number of sides of the polygon that intersect with the ray; if the count is odd, then it's inside, otherwise it's outside.

    Assuming this means the problem is "determine whether a point lies in a polygon or not", the "winding number algorithm" is probably to compute the winding number of the polygon around the point; if it's 0, then the point is outside, otherwise it's inside.

    The question is thus "how to implement this winding number algorithm".

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