/// <summary>
/// The basin angle is decided against the horizontal line [1,0]
/// </summary>
private static FP BasinAngle(AdvancingFrontNode node)
{
FP ax = node.Point.X - node.Next.Next.Point.X;
FP ay = node.Point.Y - node.Next.Next.Point.Y;
return(FP.Atan2(ay, ax));
}
private bool AngleSign()
{
Point a = (_head.Next - _head);
Point b = (_tail - _head);
return(FP.Atan2(a.Cross(b), a.Dot(b)) >= 0);
}
private FP Angle(Point p)
{
Point a = (p.Next - p);
Point b = (p.Prev - p);
return(FP.Atan2(a.Cross(b), a.Dot(b)));
}
private static FP Angle(TriangulationPoint origin, TriangulationPoint pa, TriangulationPoint pb)
{
/* Complex plane
* ab = cosA +i*sinA
* ab = (ax + ay*i)(bx + by*i) = (ax*bx + ay*by) + i(ax*by-ay*bx)
* atan2(y,x) computes the principal value of the argument function
* applied to the complex number x+iy
* Where x = ax*bx + ay*by
* y = ax*by - ay*bx
*/
FP px = origin.X;
FP py = origin.Y;
FP ax = pa.X - px;
FP ay = pa.Y - py;
FP bx = pb.X - px;
FP by = pb.Y - py;
FP x = ax * by - ay * bx;
FP y = ax * bx + ay * by;
FP angle = FP.Atan2(x, y);
return(angle);
}
/// <summary>
/// ???
/// </summary>
/// <param name="node">middle node</param>
/// <returns>the angle between 3 front nodes</returns>
private static FP HoleAngle(AdvancingFrontNode node)
{
// XXX: do we really need a signed angle for holeAngle?
// could possible save some cycles here
/* Complex plane
* ab = cosA +i*sinA
* ab = (ax + ay*i)(bx + by*i) = (ax*bx + ay*by) + i(ax*by-ay*bx)
* atan2(y,x) computes the principal value of the argument function
* applied to the complex number x+iy
* Where x = ax*bx + ay*by
* y = ax*by - ay*bx
*/
FP px = node.Point.X;
FP py = node.Point.Y;
FP ax = node.Next.Point.X - px;
FP ay = node.Next.Point.Y - py;
FP bx = node.Prev.Point.X - px;
FP by = node.Prev.Point.Y - py;
return(FP.Atan2(ax * by - ay * bx, ax * bx + ay * by));
}
