Table of Contents
Overview
ROS has several tools for interacting graphically with robotic systems.
rviz is the primary tool for visualizing your robot and its sensor data in 3Drqt is for creating a graphical user interface (GUI) in ROS.
RViz
rviz is used to visualize data in ROS in a 3D environmentIn rviz you add Display Types to the display and connect them
to information that rviz receives via ROS messages and parameters.
There are many built in Display Types , documented on the wiki .
Paths
Paths allow you to visualize a series of points that have been visited over time
These are visualized with the Path datatype using nav_msgs/Path messages
Visualization Messages
The visualization_msgs package contains
messages for displaying visual primitives in rviz using some Display Types in Rviz
Markers
Markers are the simplest visualization message
They let you draw basic shapes at specified locations
For example, spheres, cubes, cylinders, lines
See Marker Display Type for an overview
Markers are drawn by publishing marker messages
By default, the Marker display type listens on the visualization_marker topic, but this can be changed in the rviz gui or with remapping.
Markers have a header field that requires the time. Using rospy.Time() for this ensures the Marker will be drawn
Be sure to set the alpha (.a) field to be non-zero (e.g. 1) so that the marker is not drawn transparently
These C++ tutorials mostly apply to python as well since they are simply setting values in the marker message topic
Some important fields are
header contains the time at which the marker comes into existence and the frame used to interpret any coordinatesns and id are used to identify the marker. For a given namespace ns each marker has an id.
If you send a marker message with an id and ns that already exists, you modify the existing markertype What the shape of the marker is: =visualization_msgs.Marker.{ARROW | CUBE | SPHERE | CYLINDER …}
action Lets you either visualization_msgs.Marker.ADD, visualization_msgs.Marker.DELETE, or visualization_msgs.Marker.DELETEALL the markerspose this is the 3D pose of the object, used to set its position and orientation relative to header.frame_idscale used to set the size of the object. By default the markers are 1x1x1 meter.color RGBA (red, green, blue, alpha) color (0 - 1). A common error is forgetting to set the alpha to a non-zero value, otherwise the marker is completely transparentlifetime How long to display the marker before it disappears. Set to 0 for it to last forever (well at least as long as RViz remains open!)frame_locked - Controls behavior of the marker when it's parent frame moves. If this is true then the marker will always be at the same position
relative to its parent frame, even if that frame moves after the marker is drawnpoints and colors, text, mesh_resource are used for some marker types
An example of markers is here https://github.com/m-elwin/me495_markers
MarkerArray
The MarkerArray message consists of an array of Marker messages
This message type lets you publish multiple markers with a single message
rviz has a DisplayType that can subscribe to a MarkerArray message and visualize all markers in the arrayIf you are sending many markers, it is more efficient to send them as an array
InteractiveMarkers
Interactive Markers lets users manipulate markers
inside RViz. Your nodes can then respond to the actions of the user.To use interactive markers, you create an InteractiveMarkerServer
This server creates the necessary publishers and subscribers
You then provide a callback which gets called whenever the user manipulates the marker in rviz
You can call functions to change the marker in rviz
To learn interactive markers, you should go through at least the first two of these tutorials:
An additional example of using interactive markers is here
Plugins
Using markers enables you to create complex visualizations by building ROS messages
However, marker messages are quite large and using many of them can become slow
Fortunately, rviz is modular: each of the built-in DisplayTypes is actually a plugin.
You can write your own plugins in C++ that contain display logic for your own message types
Plugins can also add panels in rviz (Panels Tutorial )
Plugins can also add tools that change what the mouse does in rviz (Tools Tutorial ).
rqt
Qt is a library for creating graphical user interfacesrqt is a ROS package that enables you to create GUIs using ROS nodesIf you create a widget in Qt you can wrap that widget with rqt and use it as part of the ROS user interface
Essentially, rqt widgets can be docked and split in a parent window. These configurations can be saved
so that others can reproduce your view
Many rqt plugins come with ROS
All built-in rqt plugins can be run with rosrun
Type rosrun rqt_ then hit tab to see a list of packages.
Some of these tools are so useful and popular they have there own shortcuts on the path
Type rqt_ then tab to see these. For example
rqt_graph - seeing how nodes are connected to each other via topics
rqt_console - reading debugging output from ros nodes
rqt_logger_level - used to set debugging output level for ROS
rqt_plot - plotting message values versus time
For more advanced plotting I recommend PlotJuggler .
install sudo apt install ros-noetic-plotjuggler
There are Tutorials for creating your own plugins
rqt_plot
rqt_plot is the simplest way to draw real-time time-plots of data from ROS topicsYou can specify what fields of which topics to plot in the gui or