How to select two points from the viewer in PCL

Question

I would like to select two points from pointcloud and return the coordinates of two points. To get to the problem, I used PointPickingEvent for PCL and wrote a class containing pointcloud, a visualizer, and a vector to store the selected points. My code is:

 #include <pcl/point_cloud.h> #include <pcl/PCLPointCloud2.h> #include <pcl/io/io.h> #include <pcl/io/pcd_io.h> #include <pcl/common/io.h> #include <pcl/io/ply_io.h> #include <pcl/io/vtk_lib_io.h> #include <pcl/visualization/pcl_visualizer.h> using namespace pcl; using namespace std; class pickPoints { public: pickPoints::pickPoints () { viewer.reset (new pcl::visualization::PCLVisualizer ("Viewer", true)); viewer->registerPointPickingCallback (&pickPoints::pickCallback, *this); } ~pickPoints () {} void setInputCloud (PointCloud<PointXYZ>::Ptr cloud) { cloudTemp = cloud; } vector<float> getpoints() { return p; } void simpleViewer () { // Visualizer viewer->addPointCloud<pcl::PointXYZ>(cloudTemp, "Cloud"); viewer->resetCameraViewpoint ("Cloud"); viewer->spin(); } protected: void pickCallback (const pcl::visualization::PointPickingEvent& event, void*) { if (event.getPointIndex () == -1) return; PointXYZ picked_point1,picked_point2; event.getPoints(picked_point1.x,picked_point1.y,picked_point1.z, picked_point2.x,picked_point2.y,picked_point2.z); p.push_back(picked_point1.x); // store points p.push_back(picked_point1.y); p.push_back(picked_point1.z); p.push_back(picked_point2.x); p.push_back(picked_point2.y); p.push_back(picked_point2.z); //cout<<"first selected point: "<<p[0]<<" "<<p[1]<<" "<<p[2]<<endl; //cout<<"second selected point: "<<p[3]<<" "<<p[4]<<" "<<p[5]<<endl; } private: // Point cloud data PointCloud<pcl::PointXYZ>::Ptr cloudTemp; // The visualizer boost::shared_ptr<pcl::visualization::PCLVisualizer> viewer; // The picked point vector<float> p; }; int main() { //LOAD; PointCloud<PointXYZ>::Ptr cloud (new PointCloud<PointXYZ> ()); pcl::PolygonMesh mesh; pcl::io::loadPolygonFilePLY("test.ply", mesh); pcl::fromPCLPointCloud2(mesh.cloud, *cloud); pickPoints pickViewer; pickViewer.setInputCloud(cloud); // A pointer to a cloud pickViewer.simpleViewer(); vector<float> pointSelected; pointSelected= pickViewer.getpoints(); cout<<pointSelected[0]<<" "<<pointSelected[1]<<" "<<pointSelected[2]<<endl; cout<<pointSelected[3]<<" "<<pointSelected[4]<<" "<<pointSelected[5]<<endl; cin.get(); return 0; } 

But when the code was debugged, I received nothing. I also know that when selecting points with the left button, you should press the SHIFT button. Thank you in advance for your help!

Answer 1

I found that the getPoints () method does not work as I expected. However, getPoint () worked well. Here is the code to print the selected points and save them - this is a vector:

 std::vector<pcl::PointXYZ> selectedPoints; void pointPickingEventOccurred(const pcl::visualization::PointPickingEvent& event, void* viewer_void) { float x, y, z; if (event.getPointIndex() == -1) { return; } event.getPoint(x, y, z); std::cout << "Point coordinate ( " << x << ", " << y << ", " << z << ")" << std::endl; selectedPoints.push_back(pcl::PointXYZ(x, y, z)); } void displayCloud(pcl::PointCloud<pcl::PointXYZI>::Ptr cloud, const std::string& window_name) { if (cloud->size() < 1) { std::cout << window_name << " display failure. Cloud contains no points\n"; return; } boost::shared_ptr<pcl::visualization::PCLVisualizer> viewer(new pcl::visualization::PCLVisualizer(window_name)); pcl::visualization::PointCloudColorHandlerGenericField<pcl::PointXYZI> point_cloud_color_handler(cloud, "intensity"); viewer->addPointCloud< pcl::PointXYZI >(cloud, point_cloud_color_handler, "id"); viewer->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 2, "id"); viewer->registerKeyboardCallback(keyboardEventOccurred, (void*)viewer.get()); viewer->registerPointPickingCallback(pointPickingEventOccurred, (void*)&viewer); while (!viewer->wasStopped() && !close_window){ viewer->spinOnce(50); } close_window = false; viewer->close(); } 

You can also easily find the distances between points immediately after selecting them.

  if (selectedPoints.size() > 1) { float distance = pcl::euclideanDistance(selectedPoints[0], selectedPoints[1]); std::cout << "Distance is " << distance << std::endl; } 

The selected PointPoints object can be emptied using the keyboard if you want to start with the selection items.