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ROS pcl run-time error segmenting planes

asked 2012-07-25 13:24:49 -0500

MartinW gravatar image

Hello all,

I am trying to write a program that subscribes to the openni_launch's pointcloud topic, downsamples the data, and publishes an extracted pointcloud plane. So far the code compiles fine but upon running it produces this error:

/usr/include/boost/smart_ptr/shared_ptr.hpp:412: boost::shared_ptr<t>::reference boost::shared_ptr<t>::operator*() const [with T = sensor_msgs::PointCloud2_<std::allocator<void> >, boost::shared_ptr<t>::reference = sensor_msgs::PointCloud2_<std::allocator<void> >&]: Assertion `px != 0' failed. Aborted (core dumped)

I am unsure of where the error is coming from and would appreciate any insight. Here is the code I have written thus far:

   // Includes and whatnot

    ros::Publisher pub;
    sensor_msgs::PointCloud2::Ptr downsampled,output;

    pcl::PointCloud<pcl::PointXYZ>::Ptr output_p, downsampled_XYZ;

    void callback(const sensor_msgs::PointCloud2ConstPtr& input)
      // Do some downsampling to the point cloud
      pcl::VoxelGrid<sensor_msgs::PointCloud2> sor;
      sor.setInputCloud (input);
      sor.setLeafSize (0.01f, 0.01f, 0.01f);
      sor.filter (*downsampled);

      // Change from type sensor_msgs::PointCloud2 to pcl::PointXYZ
      pcl::fromROSMsg (*downsampled, *downsampled_XYZ);

      pcl::ModelCoefficients::Ptr coefficients (new pcl::ModelCoefficients ());
      pcl::PointIndices::Ptr inliers (new pcl::PointIndices ());
      // Create the segmentation object
      pcl::SACSegmentation<pcl::PointXYZ> seg;
      // Optional
      seg.setOptimizeCoefficients (true);
      // Mandatory
      seg.setModelType (pcl::SACMODEL_PLANE);
      seg.setMethodType (pcl::SAC_RANSAC);
      seg.setMaxIterations (1000);
      seg.setDistanceThreshold (0.01);

      // Create the filtering object
      pcl::ExtractIndices<pcl::PointXYZ> extract;

      // Segment the largest planar component from the cloud
      seg.setInputCloud (downsampled_XYZ);
      seg.segment (*inliers, *coefficients);
      if (inliers->indices.size () == 0)
              std::cerr << "Could not estimate a planar model for the given dataset." << std::endl;

      // Extract the inliers
      extract.setInputCloud (downsampled_XYZ);
      extract.setIndices (inliers);
      extract.setNegative (false);
      extract.filter (*output_p);
      std::cerr << "PointCloud representing the planar component: " << output_p->width * output_p->height << " data points." << std::endl;

      // Create the filtering object
      // extract.setNegative (true);
      // extract.filter (*cloud_f);
      // cloud_filtered.swap (cloud_f);

      pcl::toROSMsg (*output_p, *output);

      //Publish the results

    main (int argc, char** argv)
      ros::init (argc, argv, "table");
      ros::NodeHandle nh;
      ros::Subscriber sub = nh.subscribe("/camera/depth_registered/points", 1, callback);

      pub = nh.advertise<sensor_msgs::PointCloud2> ("table", 1);


      return (0);

Thank you in advance!

Cheers, Martin

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2 Answers

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answered 2012-07-25 15:00:32 -0500

I am guessing that you should allocate the memory for output_p and downsampled_XYZ when you enter the callback.

Also, one more advice, after

pcl::toROSMsg (*output_p, *output);

You should set the frame_id of output to the same value as input

output.header.frame_id = input->header.frame_id;

otherwise if you try to visualize the point cloud with rviz, it will complain because it would not know the frame of reference for output.

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Thanks! I got my program running and I've extracted the pointcloud plane of a table in front of my Kinect! I tried to add your line of code "output.header.frame_id = input->header.frame_id;" But when I did it said sensor_msgs::pointcloud2 has no member header. But I could see it in Rviz anyway!

MartinW gravatar image MartinW  ( 2012-07-26 09:26:43 -0500 )edit

answered 2013-12-01 16:16:30 -0500

sharky gravatar image

pcl::PointCloud<pcl::pointxyz>::Ptr output_p(new pcl::PointCloud<pcl::pointxyz>);

That did it for me :)

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Asked: 2012-07-25 13:24:49 -0500

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Last updated: Dec 01 '13