/// Multiply a matrix times a vector.
 public static FPVector2 Mul22(Mat33 A, FPVector2 v)
 {
     return(new FPVector2(A.ex.x * v.x + A.ey.x * v.y, A.ex.y * v.x + A.ey.y * v.y));
 }
 /// Multiply a matrix times a vector.
 public static FPVector Mul(Mat33 A, FPVector v)
 {
     return(v.x * A.ex + v.y * A.ey + v.z * A.ez);
 }