/// <summary>
/// Obtains the angle between two vectors.
/// </summary>
/// <param name="u">Vector2d.</param>
/// <param name="v">Vector2d.</param>
/// <returns>Angle in radians.</returns>
public static double AngleBetween(Vector2d u, Vector2d v)
{
double cos = DotProduct(u, v) / (u.Modulus() * v.Modulus());
if (MathHelper.IsOne(cos))
{
return(0);
}
if (MathHelper.IsOne(-cos))
{
return(Math.PI);
}
return(Math.Acos(cos));
//if (AreParallel(u, v))
//{
// if (Math.Sign(u.X) == Math.Sign(v.X) && Math.Sign(u.Y) == Math.Sign(v.Y))
// {
// return 0;
// }
// return (double)Math.PI;
//}
//Vector3d normal = Vector3d.CrossProduct(new Vector3d(u.X, u.Y, 0), new Vector3d(v.X, v.Y, 0));
//if (normal.Z < 0)
//{
// return (double)(2 * Math.PI - Math.Acos(DotProduct(u, v) / (u.Modulus() * v.Modulus())));
//}
//return (double)(Math.Acos(DotProduct(u, v) / (u.Modulus() * v.Modulus())));
}
/// <summary>
/// Obtains the angle between two vectors.
/// </summary>
/// <param name="u">Vector2d.</param>
/// <param name="v">Vector2d.</param>
/// <returns>Angle in radians.</returns>
public static double AngleBetween(Vector2d u, Vector2d v)
{
double cos = DotProduct(u, v)/(u.Modulus()*v.Modulus());
if (MathHelper.IsOne(cos))
{
return 0;
}
if (MathHelper.IsOne(-cos))
{
return Math.PI;
}
return Math.Acos(cos);
//if (AreParallel(u, v))
//{
// if (Math.Sign(u.X) == Math.Sign(v.X) && Math.Sign(u.Y) == Math.Sign(v.Y))
// {
// return 0;
// }
// return (double)Math.PI;
//}
//Vector3d normal = Vector3d.CrossProduct(new Vector3d(u.X, u.Y, 0), new Vector3d(v.X, v.Y, 0));
//if (normal.Z < 0)
//{
// return (double)(2 * Math.PI - Math.Acos(DotProduct(u, v) / (u.Modulus() * v.Modulus())));
//}
//return (double)(Math.Acos(DotProduct(u, v) / (u.Modulus() * v.Modulus())));
}