/// <summary>
/// Gets the transformation matrix for a "look at" situation. The camera is at CameraPosition
/// and looks to CameraTarget. Additionally a normalvector CameraUpVector has to be given, because the
/// Camera can turn up or down...
/// </summary>
/// <param name="CameraPosition">Position of the camera</param>
/// <param name="CameraTarget">The camera looks to that point</param>
/// <param name="CameraUpVector">Normalvector of the camera</param>
/// <example> Matrix M = LookAt(new xyz(0,10,2), new xyz(0,0,2), new xyz(0,0,1));</example>
/// <returns></returns>
public static Matrix LookAt(xyz CameraPosition, xyz CameraTarget, xyz CameraUpVector)
{
Base B = Base.UnitBase;
B = Base.LookAt(CameraPosition, CameraTarget, CameraUpVector);
return(B.ToMatrix().invert());
}