pcl_viewer visualizes everything upsidedown

[hygxy]

Hi

I've tried to modify a small part so that it can save as .pcd file, following are my changes:

pcl::PCDWriter writer;
std::chrono::high_resolution_clock::time_point p
=std::chrono::high_resolution_clock::now();
std::string now
=std::to_string((long)std::chrono::duration_caststd::chrono::milliseconds(p.time_since_epoch()).count());
writer.write("cloud_"+now +".pcd", *(s->cloud_), s->binary_);
std::cout << "saved" <<"cloud_"+now+".pcd" <<std::endl;

it also saves the data successfully, but when I use pcl_viewer to
visualize the saved .pcd file, everything is upside down and backward, only the z axis is correctly pointing to the objects.

Any ideas why is that and how can I visualize correctly? thanks in advance