YARP-based simulation with cameras yarp

This tutorial shows how to experiment with MORSE’s cameras and how to extract the images they capture. You’ll also be able to control the robot’s movement, by giving it the coordinates of its destination.


You need to install YARP and its Python bindings, by following the YARP section in the installation notes.

Before running a simulation using YARP, it is necessary to open a new shell terminal and start the yarpserver3 program:

$ yarpserver3

Configuring the scenario

We’ll use the Builder API to create the scenario and configure the robot. You can find the complete file in $MORSE_ROOT/share/morse/examples/tutorials/tutorial-2-yarp.py.

The file itself is very similar to the one created in the first tutorial. We will only add the camera, and change the middleware bindings to use YARP.

If you edit the existing file from the previous tutorial, after configuring the robot, you can add the camera like this:

camera = VideoCamera()
camera.translate(x=0.2, z=0.9)

This will add a video camera at the top of the robot.

We will also change the motion controller, to show how to use a different type of controller. We’ll use the waypoint controller, which takes as input the coordinates of the robot’s destination.

motion = Waypoint()

Configuring the middlewares

Next we need to tell MORSE how the components will communicate using middlewares. This is done with these lines:


Reading and writing data

You can now launch the simulation by pressing p on Blender’s 3Dview.

When the simulation starts, it will print the names of the YARP ports that have been created for every corresponding component. These port names can be used to connect to the component from an external program or client.

Reading from sensors

The simplest method to test the reading and writing of data is by using the terminal clients. For example, to read the robot’s Pose data through a port named /morse/atrv/pose/out, you can type the following in a terminal:

$ yarp read /data/in /morse/atrv/pose/out

Writing to actuators

To enter the robot’s destination coordinates, write them through a port named /morse/atrv/motion/in, using the command:

$ yarp write /data/out /morse/atrv/motion/in

Then type the three destination coordinates, a toleration distance and the movement speed, separated by spaces, and press Enter. For example:

5 7 0 0.5 2

Will make the robot move to within 0.5 meters of the coordinates (5.0, 7.0, 0.0), at a speed of 2 m/s.

Displaying an image from the camera

YARP provides a tool to display the images it receives through a port. This is very convenient to quickly test that you can transmit video from the simulated environment. You first need to launch the viewer application:

$ yarpview /img/read &

This creates a new port called /img/read. Next you need to connect this port to the MORSE output port that’s dedicated to the camera, /morse/atrv/camera/out. The connection is done with this command:

$ yarp connect /morse/atrv/camera/out /img/read

Now you should be able to see the output of the camera mounted on top of the robot. Tell the robot to move, using the motion controller, and you’ll see the video image being updated.