clockwise check

[PZ]

I need a &quot;something&quot; (sub or function, whatever!) that checks if 3 cartesian points of a triangle in a 2D space are clockwise or counter-clockwise.<br><br>Thanx <p> Alex<br><a href=mailtoizzapz@libero.it>pizzapz@libero.it</a><br><a href= > </a><br>*** Q(uick)BASIC RULEZ! ***

 

[logiclrd]

Three points are counter-clockwise if and only if when you rotate them to make the leftmost point point #3, the following is true:

(y2 - y3) / (x2 - x3) > (y1 - y3) / (x1 - x3)

You will need to make special cases for when multiple points have the same X coordinate. If all 3 are colinear then the result is undefined, obviously. These expressions (to the left & right of the inequality operator) are nothing more than slope calculations.