private void ReflectInternal(Circle c)
{
// Reflecting to a line?
if (IsPointOn(c.Center))
{
// Grab 2 points to reflect to P1/P2.
// We'll use the 2 points that are 120 degrees from c.Center.
Vector3D v = c.Center - this.Center;
v.RotateXY(2 * Math.PI / 3);
P1 = c.ReflectPoint(this.Center + v);
v.RotateXY(2 * Math.PI / 3);
P2 = c.ReflectPoint(this.Center + v);
Radius = double.PositiveInfinity;
Center.Empty();
}
else
{
// NOTE: We can't just reflect the center.
// See http://mathworld.wolfram.com/Inversion.html
double a = Radius;
double k = c.Radius;
Vector3D v = Center - c.Center;
double s = k * k / (v.MagSquared() - a * a);
Center = c.Center + v * s;
Radius = Math.Abs(s) * a;
P1.Empty();
P2.Empty();
}
}