/// <summary>
/// Create a quaternion that represents the rotation vector between this
/// Vector3 and a destination Vector3.
/// </summary>
/// <param name="destination">The vector we would like to rotate to.</param>
/// <returns>A quaternion representing the axis of rotation between this vector
/// and the destination vector.</returns>
public Quaternion GetRotationTo(Vector3 destination)
{
// Based on Stan Melax's algorithm in "Game Programming Gems"
Vector3 t_source = this.Normalize();
Vector3 t_dest = destination.Normalize();
float d = t_source.Dot(t_dest);
// if dot == 1 then the vectors are the same
if (d >= 1.0f)
{
return(Quaternion.Identity);
}
else if (d < (1e-6f - 1.0f))
{
Vector3 t_axis = Vector3.UnitX.Cross(this);
if (t_axis.LengthSquared() < (1e-12)) // pick another if colinear
{
t_axis = Vector3.UnitY.Cross(this);
}
t_axis.Normalize();
return(Quaternion.FromAngleAxis((float)Math.PI, t_axis));
}
else
{
float t_sqrt = (float)Math.Sqrt((1 + d) * 2.0f);
float t_invs = 1.0f / t_sqrt;
Vector3 t_cross = t_source.Cross(t_dest);
return(new Quaternion(t_cross.X * t_invs, t_cross.Y * t_invs, t_cross.Z * t_invs, t_sqrt * 0.5f).Normalize());
}
}
