tf::TransformBroadcaster in callback

Question

Hi,

So I was trying to have a transform published over tf as a result of a callback call, which made me think I had to have a tf::TransformBroadcaster as a global variable. However these can't be declared before the ros::NodeHandle is created.

I have tried using a boost::shared_ptr and almost got the hang of it but I still didn't quite understand how to use these boost pointers. Here's what I tried to do:

boost::shared_ptr<tf::TransformBroadcaster> pose_broadcaster;
void poseCallback(const nav_msgs::Odometry& pose){

    geometry_msgs::TransformStamped pose_trans;
    pose_trans.header.stamp = pose.header.stamp;
    pose_trans.header.frame_id = "odometry_frame"; 
    pose_trans.child_frame_id = "base_link";

    pose_trans.transform.translation.x = pose.pose.pose.position.x;
    pose_trans.transform.translation.y = pose.pose.pose.position.y;
    pose_trans.transform.translation.z = pose.pose.pose.position.z;
    pose_trans.transform.rotation = pose.pose.pose.orientation;
    ROS_INFO("Sending TF broadcast");
    pose_broadcaster.sendTransform(pose_trans);


}
int main(){
    ros::init(argc, argv, "pioneer_tf");
    ros::NodeHandle n;
    ros::Subscriber pose_sub=n.subscribe("pose", 1000, poseCallback);
    boost::shared_ptr<tf::TransformBroadcaster> ptr;
    pose_broadcaster= boost::shared_ptr<tf::TransformBroadcaster>(ptr);//problem here
   ros::spin();
}

I obviously got it wrong in the initialization of the pointer, what's the right way of doing it in this case?

--- EDIT ---

This problem is solved now, but I have a similar issue at the moment with a transformListener

It is basically the same set up, with a global variable (pointer declared as global and initialized in main) and the listener being called in a callback. The thing is, even though it compiles, the callback is never called, but if I comment the line where it is called inside the callback, it works and does everything normally... Any ideas of why the callback might not be called?

--- EDIT2 ---

This problem is totally solved. It was just a matter of making the TF buffer bigger and using a try/catch.

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Originally posted by Barbosa on ROS Answers with karma: 35 on 2012-10-22

Post score: 3

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Original comments

Comment by dornhege on 2012-12-14:
If you have a new question, please open a new one instead of using this old question.

Answer 1

This is not a direct answer to your question. But a simpler (yet more naive) way to do what you want. Instead of using boost:share_ptr, I usually globally declare a pointer of type tf::TransformBroadcaster first. Next, In the main function, I use new to create the object after ros::init.

//Global Variable(s)
tf::TransformBroadcaster *tb;
// Rest of the code
int main(int argc, char **argv) {
    // After ros::init
    tb = new tf::TransformBroadcaster();

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Originally posted by Mani with karma: 1704 on 2012-10-22

This answer was ACCEPTED on the original site

Post score: 4

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Original comments

Comment by Barbosa on 2012-10-29:
I will try this simpler way of doing it! Thanks!

Comment by Barbosa on 2012-12-15:
This worked fine. thank you!

Answer 2

I usually encapsulate things into a class to avoid using global variables. You could do something like this:

class PoseBroadcaster
{
public:
  PoseBroadcaster()
  {
    pose_sub_ = n_.subscribe("pose", 1000, &PoseBroadcaster::poseCallback, this);
  }
private:
  poseCallback(const nav_msgs::Odometry& pose)
  {
    geometry_msgs::TransformStamped pose_trans;
    pose_trans.header.stamp = pose.header.stamp;
    pose_trans.header.frame_id = "odometry_frame"; 
    pose_trans.child_frame_id = "base_link";

    pose_trans.transform.translation.x = pose.pose.pose.position.x;
    pose_trans.transform.translation.y = pose.pose.pose.position.y;
    pose_trans.transform.translation.z = pose.pose.pose.position.z;
    pose_trans.transform.rotation = pose.pose.pose.orientation;
    ROS_INFO("Sending TF broadcast");
    pose_broadcaster_.sendTransform(pose_trans);
  }

  ros::NodeHandle n_;
  tf::TransformBroadcaster pose_proadcaster_;
};

int main(int argc, char **argv)
{
  ros::init(argc, argv, "pioneer_tf");

  PoseBroadcaster pb;

  ros::spin();
}

I hope this helps

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Originally posted by Martin Peris with karma: 5625 on 2012-10-22

This answer was NOT ACCEPTED on the original site

Post score: 8

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Original comments

Comment by Barbosa on 2012-10-29:
I think this will help, thanks a lot. I did try this approach too but I was having some trouble with errors, maybe now this will help clear them out.