I did this last fall...
.. the key is to quickly (doesn't need to be very accurate float is probably good) the centroid then go
or since you have an ordered N-gon, you just need to know if they went clockwise or counterclockwise as they did their drawing, so you'll only need to test the winding of one triangle...
here's the code:
a -= c;
b -= c;
var ret = (int)((b.x*a.y)-(a.x-b.y));
:thumbsup: if this helps.. vote me ^ ;P thx... :thumbsup: