static void PointsToMat(
  const IntrinsicBase * cam,
  const PointFeatures & vec_feats,
  MatT & m)
{
  m.resize(2, vec_feats.size());
  typedef typename MatT::Scalar Scalar; // Output matrix type

  size_t i = 0;
  for( PointFeatures::const_iterator iter = vec_feats.begin();
    iter != vec_feats.end(); ++iter, ++i)
  {
    m.col(i) = cam->get_ud_pixel(Vec2(iter->x(), iter->y()));
  }
}