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
points[o]->pCenter->points[1]
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:
vector2 a,b,c;
a -= c;
b -= c;
var ret = (int)((b.x*a.y)-(a.x-b.y));
return (ret>=0)?((ret>0)?(1):(0)):(-1);
:thumbsup: if this helps.. vote me ^ ;P thx... :thumbsup: