多边形顶点-顺时针或逆时针 [英] polygon vertices - clockwise or counterclockwise

问题描述

我碰到了此链接 http://www.mathopenref.com/coordpolygonarea2.html

它说明了如何计算多边形的面积，并有助于识别输入的多边形顶点是顺时针还是逆时针。

It explains how to calculate the area of a polygon and helps to identify whether the polygon vertices we entered is clockwise or counter clockwise.

如果area值为+ ve，则为顺时针；如果为-nv，则为逆时针。

If area value is +ve, it is clockwise, if it is -nv then it is in counterclockwise.

我的要求是仅确定是顺时针还是逆时针。此规则是否正常运行（尽管存在链接中提到的限制）。我只有规则的多边形（不复杂，没有自相交），但顶点更多。

My requirement is to identify only whether it is clockwise or counterclockwise. Is this rule will work correctly (though there are limitations as mentioned in the link). I have only regular polygons (not complicated, no self intersections) but the vertices are more.

我对面积值的准确性不感兴趣，只是想知道环的旋转。

I am not interested in the area value accuracy, just to know the ring rotation.

对此还有其他想法。

推荐答案

对于凸多边形：

Select two edges with a common vertex. 
Lets say, edge1 is between vertex A and B. Edge2 is between vertex B and C.
Define to vectors: vect1: A----->B
                   vect2: B----->C
Cross product vect1 and vect2. 
If the result is positive, the sequence A-->B-->C is Counter-clockwise. 
If the result is negative, the sequence A-->B-->C is clockwise. 

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