Building a Custom RViz Display

Background

There are many types of data that have existing visualizations in RViz. However, if there is a message type that does not yet have a plugin to display it, there are two choices to see it in RViz.

1. Convert the message to another type, such as visualization_msgs/Marker.
2. Write a Custom RViz Display.

With the first option, there is more network traffic and limitations to how the data can be represented. It is also quick and flexible. The latter option is explained in this tutorial. It takes a bit of work, but can lead to much richer visualizations.

All of the code for this tutorial can be found in this repository <https://github.com/MetroRobots/rviz_plugin_tutorial>__. In order to see the incremental progress of the plugin written in this tutorial, the repository has different branches (step2, step3…) that can each be compiled and run as you go.

Point2D Message

We’ll be playing with a toy message defined in the rviz_plugin_tutorial_msgs package: Point2D.msg:

std_msgs/Header header
float64 x
float64 y

Boilerplate for Basic Plugin

Strap in, there’s a lot of code. You can view the full version of this code with the branch name step1.

Header File

Here are the contents of point_display.hpp

#ifndef RVIZ_PLUGIN_TUTORIAL__POINT_DISPLAY_HPP_
#define RVIZ_PLUGIN_TUTORIAL__POINT_DISPLAY_HPP_

#include <rviz_common/message_filter_display.hpp>
#include <rviz_plugin_tutorial_msgs/msg/point2_d.hpp>

namespace rviz_plugin_tutorial
{
class PointDisplay
  : public rviz_common::MessageFilterDisplay<rviz_plugin_tutorial_msgs::msg::Point2D>
{
  Q_OBJECT

protected:
  void processMessage(const rviz_plugin_tutorial_msgs::msg::Point2D::ConstSharedPtr msg) override;
};
}  // namespace rviz_plugin_tutorial

#endif  // RVIZ_PLUGIN_TUTORIAL__POINT_DISPLAY_HPP_

• We’re implementing the MessageFilterDisplay class which can be used with any message with a std_msgs/Header.
• The class is templated with our Point2D message type.
• For reasons outside the scope of this tutorial, you need the Q_OBJECT macro in there to get the QT parts of the gui to work.
• processMessage is the only method that needs to be implemented, which we’ll do in the cpp file.

Source File

point_display.cpp

#include <rviz_plugin_tutorial/point_display.hpp>
#include <rviz_common/logging.hpp>

namespace rviz_plugin_tutorial
{
void PointDisplay::processMessage(const rviz_plugin_tutorial_msgs::msg::Point2D::ConstSharedPtr msg)
{
  RVIZ_COMMON_LOG_INFO_STREAM("We got a message with frame " << msg->header.frame_id);
}
}  // namespace rviz_plugin_tutorial

#include <pluginlib/class_list_macros.hpp>
PLUGINLIB_EXPORT_CLASS(rviz_plugin_tutorial::PointDisplay, rviz_common::Display)

• The logging is not strictly necessary, but helps with debugging.
• In order for RViz to find our plugin, we need this PLUGINLIB invocation in our code (as well as other things below)

package.xml

We need the following three dependencies in our package.xml:

  <depend>pluginlib</depend>
  <depend>rviz_common</depend>
  <depend>rviz_plugin_tutorial_msgs</depend>

rviz_common_plugins.xml

<library path="point_display">
  <class type="rviz_plugin_tutorial::PointDisplay" base_class_type="rviz_common::Display">
    <description></description>
  </class>
</library>

• This is standard pluginlib code.
• The library path is the name of the library we’ll assign in the CMake.

File truncated at 100 lines see the full file