setFromMatrix4 method
Set this matrix to the upper 3x3 matrix of the Matrix4 m.
Implementation
Matrix3 setFromMatrix4(Matrix4 m) {
  final me = m.storage;
  setValues(me[0], me[4], me[8], me[1], me[5], me[9], me[2], me[6], me[10]);
  return this;
}