Given 3 2d non-colinear points in sequence, create the 3d vectors v1 = p1->p2 and v2 = p1->p3 on the z0 plane. calculate v3 = v1 X v2. if v3 has positive z then they are in counter-clockwise order, negative z then clockwise.

this is the right-hand rule, place your right hand on p1->p2 and curl your fingers onto p2->p3, if your thumb points up they go counter clockwise, if it points down they go clockwise.

i really need to look for an HTML equation editor...

In reply to Re: Clockwise or Counter-clockwise by zengargoyle
in thread Clockwise or Counter-clockwise by stu96art

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