public static bool IsCCW(PointF pt1, PointF pt2, PointF pt3)
{
Vector V21 = new Vector(pt2, pt1);
Vector v23 = new Vector(pt2, pt3);
return V21.CrossProduct(v23) > 0; // sin(angle pt2 pt1 pt3) < 0, 180<angle pt2 pt1 pt3 <360
}
public static double DistancePointLine(PointF pt, PointF lnA, PointF lnB)
{
Vector v1 = new Vector(lnA, lnB);
Vector v2 = new Vector(lnA, pt);
v1 /= v1.Magnitude;
return Math.Abs(v2.CrossProduct(v1));
}
// A * B =|A|.|B|.sin(angle AOB)
public double CrossProduct(Vector v)
{
return _x * v.Y - v.X * _y;
}
// A. B=|A|.|B|.cos(angle AOB)
public double DotProduct(Vector v)
{
return _x * v.X + _y * v.Y;
}
public static bool IsClockwise(PointF pt1, PointF pt2, PointF pt3)
{
Vector V21 = new Vector(pt2, pt1);
Vector v23 = new Vector(pt2, pt3);
return V21.CrossProduct(v23) < 0; // sin(angle pt1 pt2 pt3) > 0, 0<angle pt1 pt2 pt3 <180
}
