/// <summary>
/// Converts from euclidean to spherical coordiantes.
/// (x,y,z) = (radius, azimuth, polar)
/// </summary>
/// <returns></returns>
public Vec3d ToSpherical()
{
double r = Length;
return(new Vec3d(r, Math.Atan(Y / X), SlurMath.AcosSafe(Z / r)));
}
/// <summary>
/// Returns the minimum angle between two vectors.
/// </summary>
/// <param name="v0"></param>
/// <param name="v1"></param>
/// <returns></returns>
public static double Angle(Vec3d v0, Vec3d v1)
{
var d = v0.SquareLength * v1.SquareLength;
return(d > 0.0 ? SlurMath.AcosSafe(Dot(v0, v1) / Math.Sqrt(d)) : 0.0);
}