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Add custom ROS2 message type

ROS2 For Unity

AWSIM uses Ros2ForUnity module for ROS2 communication. ROS2 For Unity is a high-performance communication solution to connect Unity3D and ROS2 ecosystem in a ROS2 "native" way.

This document briefly guides you on how to add your custom messages to the simulation. For a detailed description, please see ROS2 For Unity Readme.

Prerequisites

ROS2 For Unity depends on a ros2cs - a C# .NET library for ROS2. You don't have to install it manually, but there are a few prerequisites that must be resolved first.

Please refer to the following prerequisites section for your OS:

Ubuntu prerequisites

Windows prerequisites

Additionall required tools:

  • Git

  • Shell:

    bash

    powershell

Build custom messages

Assumptions

To include a custom ROS2 message, you have to build ROS2 For Unity with your custom message package. The following steps will assume that:

  • the temporary ROS2 For Unity build folder is located in the home directory

    ~/

    C:\

  • your message package is called custom_msgs and is located under the path:

    ~/custom_msgs

    C:\custom_msgs

    • ROS2 version is humble (foxy and galactic are also supported, please check the current AWSIM version for more information about its ROS2 version) and is located in

    /opt/ros/humble

    C:\ros2_humble

Workspace preparation

  1. Clone ROS2 For Unity repository.

    git clone https://github.com/RobotecAI/ros2-for-unity

  2. Pull dependent repositories

    cd ~/ros2-for-unity
. /opt/ros/humble/setup.bash
./pull_repositories.sh

    cd C:\ros2-for-unity
C:\ros2_humble\local_setup.ps1
.\pull_repositories.ps1

Setup custom_msgs package

Package hosted on git repository

  1. Open ros2-for-unity/ros2_for_unity_custom_messages.repos file in your favorite editor,

  2. Modify the file contents, so it points to custom_msgs repository by changing <REPOSITORY_URL> to repository address, <BRANCH_NAME> to desired branch and <PACKAGE_NAME> to your local package name representation - in this case custom_msgs. The configured file should look as follows:

    # NOTE: Use this file if you want to build with custom messages that reside in a separate remote repo.
# NOTE: use the following format

repositories:
    src/ros2cs/custom_messages/<PACKAGE_NAME>:
        type: git
        url: <REPOSITORY_URL>
        version: <BRANCH_NAME>
    3. Now please, pull repositories to download and setup the package:

    ./pull_repositories.sh

    .\pull_repositories.ps1

Package contained on local machine

  1. Simply custom_msgs package to src/ros2cs/custom_messages directory

    cp -r ~/custom_msgs ~/ros2-for-unity/src/ros2cs/custom_messages/

    cp -r ~/custom_msgs ~/ros2-for-unity/src/ros2cs/custom_messages/

Build ROS2 For Unity

Build ROS2 For Unity using the foolowing command:

./build.sh --standalone

.\build.ps1 -standalone

Install custom_msgs to AWSIM

New ROS2 For Unity build, which you just made, contains multiple libraries that already exist in the AWSIM. To install custom_msgs and not copy all other unnecessary files, you should get the custom_msgs related libraries only and copy them to the analogous directories in AWSIM/Assets/Ros2ForUnity.

You can find them in following directories:

  • ros2-for-unity/install/asset/Ros2ForUnity/Plugins which names matches custom_msgs_*
`ros2-for-unity/install/asset/Ros2ForUnity/Plugins/Linux/x86_64/` which names matches `libcustom_msgs_*`

`ros2-for-unity/install/asset/Ros2ForUnity/Plugins/Windows/x86_64/` which names matches `custom_msgs_*`

To automate the process, you can use these commands (change <AWSIM_DIR> to your E2Simulator path and <CUSTOM_MSGS_PACKAGE_NAME> to a custom messages package):

find ~/ros2-for-unity/install/asset/Ros2ForUnity/Plugins -maxdepth 1 -name "<CUSTOM_MSGS_PACKAGE_NAME>*"    -type f -exec cp {} <AWSIM_DIR>/Assets/Ros2ForUnity/Plugins \;
find ~/ros2-for-unity/install/asset/Ros2ForUnity/Plugins/Linux/x86_64 -maxdepth 1 -name     "lib<CUSTOM_MSGS_PACKAGE_NAME>*" -type f -exec cp {} <AWSIM_DIR>/Assets/Ros2ForUnity/Plugins/Linux/x86_64 \;

Get-ChildItem C:\ros2-for-unity\install\asset\Ros2ForUnity\Plugins\* -Include @('<CUSTOM_MSGS_PACKAGE_NAME>*') | Copy-Item -Destination <AWSIM_DIR>\Assets\Ros2ForUnity\Plugins
Get-ChildItem C:\ros2-for-unity\install\asset\Ros2ForUnity\Plugins\Windows\x86_64\* -Include @('<CUSTOM_MSGS_PACKAGE_NAME>*') | Copy-Item -Destination <AWSIM_DIR>\Assets\Ros2ForUnity\Plugins\Windows\x86_64