How to convert PCLPointCloud2 to PointCloud<T> in Hydro?

Question

I've been referencing the ROS PCL tutorials (http://wiki.ros.org/pcl/Tutorials) to get up to speed on using the library in ROS, but I'm running into a little bit of trouble with the conversion to Hydro. According to the note under "sensor_msgs/PointCloud2", the sensor_msgs::PointCloud2 type previously used to send point clouds as ROS messages has been deprecated in favor of pcl::PCLPointCloud2. That section of the tutorial tells you exactly how to adapt your code in the example for the new type - awesome!

However, inside my node, I'm doing some correspondence grouping work, and the code that I've already gotten working outside of ROS uses a pcl::PointCloudpcl::PointXYZ, so I went down to the "pcl/PointCloud" section and looked for the same migration instructions - no dice. I looked at the migration instructions (http://wiki.ros.org/hydro/Migration) and the API, tried both of these options, where I've substituted the variable names for their types:

[pcl::PointCloud< pcl::PointXYZ >] = [const pcl::PCLPointCloud2ConstPtr&];
pcl::fromROSMsg( *[const pcl::PCLPointCloud2ConstPtr&], [pcl::PointCloud< pcl::PointXYZ >] );
[pcl::PointCloud< pcl::PointXYZ >] = [const pcl::PCLPointCloud2ConstPtr&].makeShared();

Both throw an error, and I've also tried calling fromROSMsg with namespace pcl_conversions. I'm assuming that I am missing something in some piece of documentation, but I can't seem to figure it out. Any help would be appreciated.

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Originally posted by teddybouch on ROS Answers with karma: 320 on 2013-11-05

Post score: 0

Answer 1

I was just working on this same thing and I saw your post! It helped me figure it out.

You are using the depreciated conversion.h file by calling fromROSMsg. Try this:

#include <ros/ros.h>
#include <sensor_msgs/PointCloud2.h>
#include <pcl/conversions.h> //I believe you were using pcl/ros/conversion.h
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>

#include <iostream>
#include <pcl/io/pcd_io.h>

#include <pcl/PCLPointCloud2.h>
#include <pcl_conversions/pcl_conversions.h>

void 
cloud_cb (const sensor_msgs::PointCloud2 input)
{
  pcl::PCLPointCloud2 pcl_pc;
  pcl_conversions::toPCL(input, pcl_pc);

  pcl::PointCloud<pcl::PointXYZ> cloud;

  pcl::fromPCLPointCloud2(pcl_pc, cloud);
  pcl::YOUR_PCL_FUNCTION(cloud,...);
}

int
main (int argc, char** argv)
{
  // Initialize ROS
  ros::init (argc, argv, "pointcloud2_to_pcd");
  ros::NodeHandle nh;

  // Create a ROS subscriber for the input point cloud
  ros::Subscriber sub = nh.subscribe ("cloud", 1, cloud_cb);

  // Spin
  ros::spin ();
}

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Originally posted by pwong with karma: 447 on 2013-11-05

This answer was ACCEPTED on the original site

Post score: 5

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Original comments

Comment by teddybouch on 2013-11-06:
I found the documentation for converting from sensor_msgs::PointCloud2 to pcl::PointCloudpcl::PointXYZ. The problem that I've run into is that the ROS PCL tutorial indicates that, for Hydro, the input type for the cloud_cb in your example should be pcl::PCLPointCloud2 instead.

Comment by pwong on 2013-11-06:
I'm using Hydro myself. For the call back function, my sensor is still publishing out in sensor_msgs::PointCloud2, so I'm still subscribing to that type. Converting to pcl::PCLPointCloud2 format before publishing would be better idea though.

Comment by ZsurzsaLaszlo on 2013-11-18:
Hey, I try to do the same thing as shown here. The difference is that I'm doing it for fuerte. I did compile pcl_conversions but I can't load it in my code. How did you proceed in youre case?

Comment by pwong on 2013-11-18:
What exactly do you mean by 'load it in my code'?

Comment by ZsurzsaLaszlo on 2013-11-18:
I compiled PCL from source now I can't use ros msgs so I wanted to use this package. Although it compiles everything. #include <pcl_conversions/pcl_conversions.h> gives me error. I hope you can help me with this. I use FUERTE.

Comment by pwong on 2013-11-18:
I don't know if Fuerte depreciated sensor_msgs::PointCloud2, but in case it didn't, you can't just go with this set up?

http://wiki.ros.org/pcl/Tutorials

I also don't know if the newest version of pcl takes type pcl::PCLPointCloud2 exclusively. Sorry, I don't know if that was very helpful or not.