/// <summary>
 /// Inverts this rigid transformation (multiplicative inverse).
 /// this = [Rot^T,-Rot^T Trans]
 /// </summary>
 public void Invert()
 {
     Rot.Invert();
     Trans = -Rot.TransformDir(Trans);
 }
 /// <summary>
 /// Transforms a direction vector.
 /// </summary>
 public V2f TransformDir(V2f v)
 {
     return(Rot2f.TransformDir(this, v));
 }