ROS bridge installation

The ROS bridge enables two-way communication between ROS and CARLA. The information from the CARLA server is translated to ROS topics. In the same way, the messages sent between nodes in ROS get translated to commands to be applied in CARLA.

• Requirements
  • Python2
• Bridge installation
  • A. Using Debian repository
  • B. Using source repository
• Run the ROS bridge
• Setting CARLA

Requirements

Make sure that both requirements work properly before continuing with the installation.

• ROS Kinetic/Melodic — Install the ROS version corresponding to your system. Additional ROS packages may be required, depending on the user needs. rviz is highly recommended to visualize ROS data.
  • ROS Melodic — For Ubuntu 16.04 (Xenial).
  • ROS Kinetic — For Ubuntu 18.04 (Bionic).
  • ROS Noetic — For Ubuntu 20.04 (Focal).
• CARLA 0.9.7 or later — Previous versions are not compatible with the ROS bridge. Follow the quick start installation or make the build for Linux.

Python

The version of Python needed to run the ROS bridge depends on the ROS version being used.

• ROS Melodic and ROS Kinetic — Python2.
• ROS Noetic — Python3.

All the CARLA releases provide support for Python3, so ROS Noetic users do not need more preparation. However, ROS Melodic/Kinetic users cannot use the latest CARLA release packages. Since 0.9.10 (included), CARLA does not provide support for Python2, so users will have to make the build from source, and compile the PythonAPI for Python2.

• Run the following command in the root CARLA directory of your Linux build to compile the PythonAPI for Python2.

make PythonAPI ARGS="--python-version=2"

Bridge installation

A. Using Debian repository

Set up the Debian repository in the system.

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 1AF1527DE64CB8D9
sudo add-apt-repository "deb [arch=amd64] http://dist.carla.org/carla $(lsb_release -sc) main"

Install the ROS bridge, and check for the installation in the /opt/ folder.

sudo apt-get update # Update the Debian package index
sudo apt-get install carla-ros-bridge # Install the latest ROS bridge version, or update the current installation

This repository contains features from CARLA 0.9.10 and later versions. To install a specific version add the version tag to the installation command.

sudo apt-get install carla-ros-bridge=0.9.10-1 # In this case, "0.9.10" refers to the ROS bridge version, and "1" to the Debian revision  

B. Using source repository

A catkin workspace is needed to use the ROS bridge. It should be cloned and built in there. The following code creates a new workspace, and clones the repository in there.

# Setup folder structure
mkdir -p ~/carla-ros-bridge/catkin_ws/src
cd ~/carla-ros-bridge
git clone https://github.com/carla-simulator/ros-bridge.git
cd ros-bridge
git submodule update --init
cd ../catkin_ws/src
ln -s ../../ros-bridge
source /opt/ros/kinetic/setup.bash # Watch out, this sets ROS Kinetic 
cd ..

# Install required ros-dependencies
rosdep update
rosdep install --from-paths src --ignore-src -r

# Build
catkin_make

Run the ROS bridge

1) Run CARLA. The way to do so depends on the CARLA installation.

• Quick start/release package. ./CarlaUE4.sh in carla/.
• Debian installation. ./CarlaUE4.sh in opt/carla-simulator/.
• Build installation. make launch in carla/.

2) Add the source path. The source path for the workspace has to be added, so that the ROS bridge can be used from a terminal.

• Source for apt ROS bridge.

source /opt/carla-ros-bridge/<melodic or kinetic>/setup.bash

• Source for ROS bridge repository download.

source ~/carla-ros-bridge/catkin_ws/devel/setup.bash

3) Start the ROS bridge. Use any of the different launch files available to check the installation. Here are some suggestions.

# Option 1: start the ros bridge
roslaunch carla_ros_bridge carla_ros_bridge.launch

# Option 2: start the ros bridge together with RVIZ
roslaunch carla_ros_bridge carla_ros_bridge_with_rviz.launch

# Option 3: start the ros bridge together with an example ego vehicle
roslaunch carla_ros_bridge carla_ros_bridge_with_example_ego_vehicle.launch

    export PYTHONPATH=$PYTHONPATH:<path/to/carla/>/PythonAPI/<your_egg_file>

python3 -c 'import carla;print("Success")'

Setting CARLA

To modify the way CARLA works along with the ROS bridge, edit share/carla_ros_bridge/config/settings.yaml.

• Host/port. Network settings to connect to CARLA using a Python client.
• Synchronous mode.
  • If false (default). Data is published on every world.on_tick() and every sensor.listen() callbacks.
  • If true The bridge waits for all the sensor messages expected before the next tick. This might slow down the overall simulation but ensures reproducible results.
• Wait for vehicle command. In synchronous mode, pauses the tick until a vehicle control is completed.
• Simulation time-step. Simulation time (delta seconds) between simulation steps. It must be lower than 0.1. Take a look at the documentation to learn more about this.
• Role names for the Ego vehicles. Role names to identify ego vehicles. These will be controllable from ROS and thus, relevant topics will be created.

Synchronous mode

To control the step update when in synchronous mode, use the following topic. The message contains a constant named command that allows to Pause/Play the simulation, and execute a single step.

The Control rqt plugin launches a new window with a simple interface. It is used to manage the steps and publish in the corresponding topic. Simply run the following when CARLA in synchronous mode.

rqt --standalone rqt_carla_control