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Running the Nav2 + slam_toolbox Example

Table of Contents

Start RViz in the Docker container

This section assumes you have already set up your environment according to the guide here

  • In a terminal on your host OS, run the following:

    docker run -it --rm -p 6080:80 -p 10000:10000 --shm-size=1024m unity-robotics:nav2-slam-example

  • In a web browser connect to http://127.0.0.1:6080 and follow the steps below:

    • Click on the bottom left system menu and select System Tools > LXTerminal connecting to the docker container

    • In the Terminal run:

      ros2 launch unity_slam_example unity_slam_example.py

  • If everything is configured correctly, you should see an RViz window open that looks like this:

Blank, pre-configured RViz window

You may also see the following message being spammed in the console:

[controller_server-4] [INFO] [1626978106.918019100] [local_costmap.local_costmap]: Timed out waiting for transform from base_link to odom to become available, tf error: Invalid frame ID "base_link" passed to canTransform argument source_frame - frame does not exist

This is normal, as the transform frames will be sent from Unity, which hasn't started yet.

(Optional) Launching ROS2 components manually

  • If you are managing your own ROS2 environment, you can launch the example manually by using: 
    ros2 launch unity_slam_example unity_slam_example.py

If this doesn't work, you may need to first colcon build the workspace or source install/local_setup.bash to properly populate your ROS2 paths.

Start the Unity simulation

This section assumes you have already set up your Unity environment according to the guide here.

  • With the SimpleWareHouseScene open, simply press the Play button at the top of the Editor.

animation of Play button being pressed and simulation starting

If the ROS2 nodes were already launched, you should see flashing, non-red arrows in the top-left HUD to indicate Unity is communicating with ROS.

Interacting with this Example

  • Once both the ROS2 nodes and Unity simulation are started and communicating correctly, you should see the occupancy map start to fill up in RViz.

animation of RViz rendering occupancy map and laser scans

  • The TurtleBot is now localizing AND mapping, simultaneously! Now, to do navigation, click the 2D Goal Pose button, and left-click, drag, and release a location in RViz to send a commanded pose to the navigation stack.

animation of clicking 2D goal pose in RViz

Congratulations! The TurtleBot is now navigating the map as it generates it from laserscan data published from Unity.

While the Nav2 stack is pretty robust to most goal inputs, it may occasionally crash or otherwise reach a state where it no longer responds as expected. These issues can most of the time be fixed by simply killing and restarting the nav2 nodes, and pressing Play twice in Unity to stop and restart the simulation.

Getting Started with Visualizations

The next step is to add visualizations in Unity using the Visualizations Package. Proceed to Visualizing with Unity.

Troubleshooting

If you get the following error:

launch.invalid_launch_file_error.InvalidLaunchFileError: Caught exception when trying to load file of format [py]: "package 'ros_tcp_endpoint' not found, searching: ['/home/rosdev/colcon_ws/install/unity_slam_example', '/opt/ros/foxy']"

You likely forgot to check out the submodules when following the setup instructions. You will need to check them out with git submodule update --init --recursive and re-build the container as per the instructions in the linked page.