distance-transform

I want to use this package to estimate free distances to close-in obstacles. However, distance always gives zero, despite distmap seems to be correct in Rviz.

  if(dist_map_ptr_->process(costmap_)){
    auto dist_grid_ptr = dist_map_ptr_->getDistanceFieldObstacle();
    double distance = dist_grid_ptr->atCell(mx, my);
    std::cout<< distance << std::endl;

    au