Hi Len,

re:
> For the algorithm you suggested, I'm thinking maybe I could take the entry angle (tangent of the first point I think)
> and rotate the mid and end points to align with cartesian before doing the calculation.

The property of clockwise/counter-clockwise direction is invariant to 2D rotation.

It looks like you have a typo in the isClockwise2() function.

You have this:

function isClockwise2(k,l,m)
{
	var XLK = l.x - k.x;
	var XMK = m.x - k.x;
>>>	var YLK = m.y - k.y;        <<<
	var YMK = m.y - k.y;

	signed_area = 0.5 * (( XLK*YMK ) - ( XMK*YLK ));
	if( signed_area > 0)
		return 1;
	else if( signed_area < 0)
		return -1;
	else 
		return 0;
}

There is a typo in the line marked with >>> <<< , it should be
(from http://moi3d.com/forum/index.php?webtag=MOI&msg=11521.42):

var YLK = l.y - k.y;

- Michael