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Note: This tutorial assumes that you have completed the previous tutorials: ROS Tutorials.
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Interactive Markers: Writing a Simple Interactive Marker Server

Description: This tutorial explains how to setup a minimalist server which manages a single interactive marker.

Tutorial Level: BEGINNER

Next Tutorial: Interactive Markers: Basic Controls

The simple_marker tutorial explained

If you run the simple_marker example from interactive_marker_tutorials as described in the previous tutorial, you will see this in RViz:

The simple_marker example showing in RViz

It shows the single interactive marker provided by the server node. Click on the arrow to move the box. What you will also see is that the server node prints out the current position of the marker each time you change it in RViz.

This is the code of the server node:

https://raw.githubusercontent.com/ros-visualization/visualization_tutorials/indigo-devel/interactive_marker_tutorials/src/simple_marker.cpp

  97 #include <ros/ros.h>
  98 
  99 #include <interactive_markers/interactive_marker_server.h>
 100 
 101 void processFeedback(
 102     const visualization_msgs::InteractiveMarkerFeedbackConstPtr &feedback )
 103 {
 104   ROS_INFO_STREAM( feedback->marker_name << " is now at "
 105       << feedback->pose.position.x << ", " << feedback->pose.position.y
 106       << ", " << feedback->pose.position.z );
 107 }
 108 
 109 int main(int argc, char** argv)
 110 {
 111   ros::init(argc, argv, "simple_marker");
 112 
 113   // create an interactive marker server on the topic namespace simple_marker
 114   interactive_markers::InteractiveMarkerServer server("simple_marker");
 115 
 116   // create an interactive marker for our server
 117   visualization_msgs::InteractiveMarker int_marker;
 118   int_marker.header.frame_id = "base_link";
 119   int_marker.header.stamp=ros::Time::now();
 120   int_marker.name = "my_marker";
 121   int_marker.description = "Simple 1-DOF Control";
 122 
 123   // create a grey box marker
 124   visualization_msgs::Marker box_marker;
 125   box_marker.type = visualization_msgs::Marker::CUBE;
 126   box_marker.scale.x = 0.45;
 127   box_marker.scale.y = 0.45;
 128   box_marker.scale.z = 0.45;
 129   box_marker.color.r = 0.5;
 130   box_marker.color.g = 0.5;
 131   box_marker.color.b = 0.5;
 132   box_marker.color.a = 1.0;
 133 
 134   // create a non-interactive control which contains the box
 135   visualization_msgs::InteractiveMarkerControl box_control;
 136   box_control.always_visible = true;
 137   box_control.markers.push_back( box_marker );
 138 
 139   // add the control to the interactive marker
 140   int_marker.controls.push_back( box_control );
 141 
 142   // create a control which will move the box
 143   // this control does not contain any markers,
 144   // which will cause RViz to insert two arrows
 145   visualization_msgs::InteractiveMarkerControl rotate_control;
 146   rotate_control.name = "move_x";
 147   rotate_control.interaction_mode =
 148       visualization_msgs::InteractiveMarkerControl::MOVE_AXIS;
 149 
 150   // add the control to the interactive marker
 151   int_marker.controls.push_back(rotate_control);
 152 
 153   // add the interactive marker to our collection &
 154   // tell the server to call processFeedback() when feedback arrives for it
 155   server.insert(int_marker, &processFeedback);
 156 
 157   // 'commit' changes and send to all clients
 158   server.applyChanges();
 159 
 160   // start the ROS main loop
 161   ros::spin();
 162 }

What this does is the following:

Note that when calling insert, the server object will internally only push the new marker onto a waiting list. Once you call applyChanges, it will incorporate it into it's publicly visible set of interactive markers and send it to all connected clients.

That's all there is. You are now ready to go on to the next tutorial: Interactive Markers: Basic Controls.


2019-05-18 13:18