Wrench Marker

This package contains both a library and an executable node.

The wrench_marker_publisher node can be used to generate marker messages out of wrenches published to a ROS topic.

It internally uses the wrench_marker library. This library exports the wrench_marker/wrench_marker.h header, in which a single class is declared. It can be used to generate rviz markers (i.e. visualization_msgs/MarkerArray messages) from wrenches (i.e. geometry_msgs/Wrench messages) that use several arrow markers to display the wrench in rviz. The responsibility of publishing the message lies in user code.

wrench_marker_publisher node

The wrench_marker_publisher node subscribes to geometry_msgs/WrenchStamped messages in the wrench topic, and publishes a marker array to visualize it in wrench_marker topic.

The generated marker can be uniformly scaled by setting the private wrench_marker_scale parameter.

To run it with a different input topic and/or scaling factor run.

rosrun wrench_marker wrench_marker_publisher wrench:=INPUT_TOPIC _wrench_marker_scale:=SCALING_FACTOR

Fine grained scaling control is applied (after initializing default values based on the general wrench_marker_scale) by reading from the following private parameters:

• arrow_shaft_diameter
• arrow_head_diameter
• force_arrow_scale
• torque_arrow_scale
• torque_arrow_separation

wrench_marker library basic usage

Sample code for how to use the wrench_marker library follows.

#include <wrench_marker/wrench_marker.h>

int main( int argc, char** argv )
{
  wrench_marker::WrenchMarker my_wrench_marker;

  geometry_msgs::WrenchStamped wrench_msg;
  // Fill wrench data

  const visualization_msgs::MarkerArray& marker_array = my_wrench_marker.getMarker( wrench_msg );
  // Publish marker_array

  return 0;
}

A more ellaborate use-case can be found in wrench_marker_publisher.cpp

Reference

The full signature of the constructor is:

WrenchMarker::WrenchMarker(
  const WrenchMarkerScaleOptions scale_options = WrenchMarkerScaleOptions();
  const std::string& ns = "wrench",
  visualization_msgs::MarkerArray* msg = 0 );

• scale_options is an structure which can be used to control the scaling/positioning of the different arrows in the generated marker
• ns is the namespace for the markers
• msg is a pre-allocated MarkerArray message for internal use¹

There are two overloads for getMarker.

The first one is:

const visualization_msgs::MarkerArray& WrenchMarker::getMarker(
  const geometry_msgs::WrenchStamped& wrench_stamped,
  const ros::Time& time = ros::Time::now() );

This will return a marker which will be displayed on top of the frame specified in wrench_stamped.header.frame_id.

The more complete one is:

const visualization_msgs::MarkerArray& WrenchMarker::getMarker(
  const geometry_msgs::Wrench& wrench,
  const std::string& frame,
  const geometry_msgs::Point& pos = geometry_msgs::Point(),
  const ros::Time& time = ros::Time::now() );

Here, the non stamped wrench is considered to be expressed in reference frame specified in frame, but referring to (and displayed at) the position given in pos. Note that pos is considered to be relative to frame.

---

¹ Providing an allocated message is useful if used in conjunction with realtime_tools::RealtimePublisher.