/// <summary>
/// Initializes an circle from three points.
/// https://github.com/sergarrido/random/tree/master/circle3d
/// </summary>
/// <param name="pt1">Start point of the arc.</param>
/// <param name="pt2">Interior point on arc.</param>
/// <param name="pt3">End point of the arc.</param>
public Circle(Point3 pt1, Point3 pt2, Point3 pt3)
{
if (!pt1.IsValid)
{
throw new Exception("The first point is not valid.");
}
if (!pt2.IsValid)
{
throw new Exception("The second point is not valid.");
}
if (!pt3.IsValid)
{
throw new Exception("The third point is not valid.");
}
Point3 center = Trigonometry.EquidistantPoint(pt1, pt2, pt3);
Vector3 normal = Vector3.ZAxis.PerpendicularTo(pt1, pt2, pt3);
Vector3 xDir = pt1 - center;
Vector3 yDir = Vector3.CrossProduct(normal, xDir);
Plane = new Plane(center, xDir, yDir);
Radius = xDir.Length;
_length = Math.Abs(2.0 * Math.PI * Radius);
ToNurbs();
}