carla_spawn_objects.md

Carla Spawn Objects

The carla_spawn_objects package is used to spawn actors (vehicles, sensors, walkers) and to attach sensors to them.

• Configuration and sensor setup
  • Create the configuration
• Spawning Vehicles
  • Respawning vehicles
• Spawning Sensors
  • Attach sensors to an existing vehicle

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Configuration and sensor setup

Objects and their attached sensors are defined through a .json file. The default location of this file is within carla_spawn_objects/config/objects.json. To change the location, pass the path to the file via the private ROS parameter, objects_definition_file, when you launch the package:

    # ROS 1
    roslaunch carla_spawn_objects carla_spawn_objects.launch objects_definition_file:=path/to/objects.json

    # ROS 2
    ros2 launch carla_spawn_objects carla_spawn_objects.launch.py objects_definition_file:=path/to/objects.json

Create the configuration

You can find an example in the ros-bridge repository as well as follow this outline to create your own configuration and sensor setup:

{
"objects":
    [
        {
            "type": "<SENSOR-TYPE>",
            "id": "<NAME>",
            "spawn_point": {"x": 0.0, "y": 0.0, "z": 0.0, "roll": 0.0, "pitch": 0.0, "yaw": 0.0},
            <ADDITIONAL-SENSOR-ATTRIBUTES>
        },
        {
            "type": "<VEHICLE-TYPE>",
            "id": "<VEHICLE-NAME>",
            "spawn_point": {"x": -11.1, "y": 138.5, "z": 0.2, "roll": 0.0, "pitch": 0.0, "yaw": -178.7},
            "sensors":
                [
                <SENSORS-TO-ATTACH-TO-VEHICLE>
                ]
        }
        ...
    ]
}

!!! Note Remember when directly defining positions that ROS uses a right hand system

All sensor attributes are defined as described in the blueprint library.

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Spawning vehicles

• If no specific spawn point is defined, vehicles will be spawned at a random location.

• To define the position at which a vehicle will be spawned, there are two choices:

  • Pass the desired position to a ROS parameter spawn_point_<VEHICLE-NAME>. <VEHICLE-NAME> will be the id you gave the vehicle in the .json file:

      # ROS 1
      roslaunch carla_spawn_objects carla_spawn_objects.launch spawn_point_<VEHICLE-NAME>:=x,y,z,roll,pitch,yaw
    
      # ROS 2
      ros2 launch carla_spawn_objects carla_spawn_objects.launch.py spawn_point_<VEHICLE-NAME>:=x,y,z,roll,pitch,yaw
    

  • Define the initial position directly in the .json file:

      {
      "type": "vehicle.*",
      "id": "ego_vehicle",
      "spawn_point": {"x": -11.1, "y": 138.5, "z": 0.2, "roll": 0.0, "pitch": 0.0, "yaw": -178.7},
      }
    

Respawning vehicles

A vehicle can be respawned to a different location during a simulation by publishing to the topic /carla/<ROLE NAME>/<CONTROLLER_ID>/initialpose. To use this functionality:

1. Attach an actor.pseudo.control pseudo-actor to the vehicle in the .json file. It should have the same id value as the value passed as <CONTROLLER_ID> used to publish to the topic:

    {
    "type": "vehicle.*",
    "id": "ego_vehicle",
    "sensors":
    [
        {
        "type": "actor.pseudo.control",
        "id": "control"
        }
    ]
    }
   

2. Launch the set_inital_pose node, passing the <CONTROLLER_ID> as an argument to the ROS parameter controller_id (default = 'control'):

    roslaunch carla_spawn_objects set_initial_pose.launch controller_id:=<CONTROLLER_ID>
   

3. The preferred way to publish the message to set the new position is by using the 2D Pose Estimate button available in the RVIZ interface. You can then click on the viewport of the map to respawn in that position. This will delete the current ego_vehicle and respawn it at the specified position.

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Spawning Sensors

• The initial position for a sensor should be defined directly in the .json file, as shown above for vehicles.
• The spawn point for a sensor attached to a vehicle is considered relative to the vehicle.

Attach sensors to an existing vehicle

Sensors can be attached to an already existing vehicle. To do so:

1. Define the pseudo sensor sensor.pseudo.actor_list in the .json file. This will give access to a list of already existing actors.

    ...
    {
        "type": "sensor.pseudo.actor_list",
        "id": "actor_list"
    },
   

2. Define the rest of the sensors as required.

3. Launch the node with the spawn_sensors_only parameter set to True. This will check if an actor with the same id and type as the one specified in the .json file is already active and if so, attach the sensors to this actor.

    # ROS 1
    roslaunch carla_spawn_objects carla_spawn_objects.launch spawn_sensors_only:=True
   
    # ROS 2
    ros2 launch carla_spawn_objects carla_spawn_objects.launch.py spawn_sensors_only:=True
   

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