I’ve updated the lib : http://code.google.com/p/biga/
+ added some improvements to the circumcircle computation thanks to the link you gave. now it works +/- 10 times faster :)

I played a bit with the sources, and it seems that the algorithm for projecting a point on a line can be optimized (in the class GeomUtil). I have seen that the projection can return a point with a pair [x, y] null. This is due to computation, which in some cases (a vertical line), returns an infinite value (m), and therefore a pair [x, y] null.
Another method for the projection:

static public function projection(p:Point, a:Point, b:Point):Point
{
var len:Number = Math.sqrt((b.x – a.x) * (b.x – a.x) + (b.y – a.y) * (b.y – a.y));
var r:Number = (((a.y – p.y) * (a.y – b.y)) – ((a.x – p.x) * (b.x – a.x))) / (len * len);

var px:Number = a.x + r * (b.x – a.x);
var py:Number = a.y + r * (b.y – a.y);

return new Point(px, py);
}

The mathematical explanation: http://bit.ly/lYfant

And continuing to make us dream ;)

Héhé! t’as vu cette belle réponse en anglais !

Really good work like many times !

Thomas