Pause and Run simulation

A Gazebo transport API is exposed to allow starting and stopping the simulation. It's possible to call this API using the command line or through the GUI.

To repeat this demo, run the default world:

gz sim default.sdf

Transport API

When Gazebo is run headless, this is an easy way to start the simulation.

To pause and play over the transport API, we should call the service /world/<world_name>/control and fill the request message type gz.msgs.WorldControl. This service returns a gz.msgs.Boolean with the status of the request (true means everything was fine, false otherwise).

The WorldControl message contains a pause field for starting and stopping the simulation.

To start the simulation:

gz service -s /world/default/control --reqtype gz.msgs.WorldControl --reptype gz.msgs.Boolean --timeout 3000 --req 'pause: false'

To pause the simulation:

gz service -s /world/default/control --reqtype gz.msgs.WorldControl --reptype gz.msgs.Boolean --timeout 3000 --req 'pause: true'

When paused, time will stop in Gazebo, and the physics will not be running.

To check the current state of the simulator, check the paused field in /stats like so:

gz topic --echo --topic /stats -n 1

If the simulator is currently paused but was running before, we would see something similar to this:

sim_time {
  sec: 8
  nsec: 707000000
}
real_time {
  sec: 8
  nsec: 824323281
}
iterations: 8707
real_time_factor: 0.998022916602211

GUI

We included a button in the World Control plugin allowing to start and stop the simulation from the GUI.