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Ros2Extension.md

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RGL ROS2 extension

The extension introduces the node to publish PointCloud2 messages to ROS2. RGL creates a ROS2 node named RobotecGPULidar and registers publishers based on constructed RGL nodes.

Supported ROS2 distributions:

  • Humble

Supported DDS implementations for ROS2 standalone build:

  • Eclipse Cyclone DDS
  • eProsima Fast DDS

Building

RGL ROS2 extension can be built in two flavors:

  • standalone - ROS2 installation is not required on the target machine. RGL build will include all required ROS2 dependencies.
  • overlay - Assumes the existence of supported ROS2 installation on the target machine. RGL will try to use the existing installation of ROS2 dependencies.

Before building RGL PCL extension, it is necessary to get the required dependencies. For some, the process has been automated - run setup.py --install-ros2-deps to get them.

Ubuntu 22

Prerequisites

  • Requirements listed in the main README (section Building on Ubuntu).
  • ROS2 installed on the system and sourced.
  • For standalone build:
    • ROS2 cyclonedds and fastrtps packages.
    • patchelf tool. 
      apt install -y ros-${ROS_DISTRO}-cyclonedds ros-${ROS_DISTRO}-rmw-cyclonedds-cpp
apt install -y ros-${ROS_DISTRO}-fastrtps ros-${ROS_DISTRO}-rmw-fastrtps-cpp
apt install -y ros-${ROS_DISTRO}-radar-msgs
apt install patchelf

Steps for overlay

  1. Use script setup.py with option --with-ros2.

Steps for standalone

  1. Use script setup.py with option --with-ros2-standalone
    • You can specify run-time search path(s) of RGL dependencies by adding the option --lib-rpath <paths>. This can be useful if you want RGL to search for ROS2 libraries in a different directory than RGL, e.g., if you work with a library providing its own ROS2 libraries, such as ROS2ForUnity.
  2. Copy all ROS2 libraries from <build-dir>/ros2_standalone/ to libRobotecGPULidar.so location (or location defined with --lib-rpath).

Tips for integrating RGL + ROS2 standalone with Unity and ROS2ForUnity plugin.

  1. Build RGL with the command: 
    ./setup.py --with-ros2-standalone --lib-rpath \$ORIGIN/../../../../Ros2ForUnity/Plugins/Linux/x86_64/
    $ORIGIN represents the directory in which an object (library) originated. It is resolved at run-time.
    Your rpath may differ. It depends on your relative location between RGLUnityPlugin and Ros2ForUnity.
  2. Copy library <build-dir>/libRobotecGPULidar.so to the appropriate directory in your RGLUnityPlugin.
  3. Copy all ROS2 libraries from <build-dir>/ros2_standalone/ to Ros2ForUnity\Plugins\Linux\x86_64 directory. Skip for duplicates.

RGL's ROS2 standalone build is dependent on ROS2ForUnity's ROS2 standalone build. RobotecGPULidar library will find ROS2 because we have set the appropriate rpath for the ROS2 libraries in ROS2ForUnity.

Windows

Prerequisites

  • Requirements listed in the main README (section Building on Windows).
  • ROS2 installed on the system and sourced.
  • Fixed ROS2 logging macros in rclcpp package to make it compile with C++20. More about this bug: github PR.
    • Use fix_ros2_humble.py script to apply those changes: 
      python ros2_standalone\fix_ros2_humble.py <your-path-to-ros2>
  • For standalone build:
    • If you have installed ROS2 from pre-built binaries, there is rmw_cyclonedds_cpp package missing. You need to build this one from the source:
      1. Make sure you have installed ROS2 prerequisites.
      2. A good practice is to disable Windows path limits, see.
      3. Run x64 Native Tools Command Prompt for VS 2019, setup development folder (e.g., C:\rosrmw), clone ROS2 repos, and build: 
        md \rosrmw\src
cd \rosrmw
vcs import --input https://raw.githubusercontent.com/ros2/ros2/humble/ros2.repos src
colcon build --merge-install --packages-up-to rmw_cyclonedds_cpp
      4. Before building RGL, source rosrmw workspace: call C:\rosrmw\install\setup.bat.

Steps for overlay

  1. Run x64 Native Tools Command Prompt for VS 2019 and navigate to RGL repository.
  2. Run python setup.py --with-ros2 command to build RGL with ROS2 extension.

Steps for standalone

  1. Run x64 Native Tools Command Prompt for VS 2019 and navigate to RGL repository.
  2. Run python setup.py --with-ros2-standalone command to build RGL with ROS2 extension and install ROS2 libraries.
  3. Copy all ROS2 libraries from <build-dir>/ros2_standalone/ into RobotecGPULidar.dll location, or extend environment variable Path appropriately.

Tips for integrating RGL + ROS2 standalone with Unity and ROS2ForUnity plugin.

  1. Build RGL with ROS2 standalone as described above.
  2. Copy <build-dir>/RobotecGPULidar.dll and all depend libraries located in <build-dir> to the appropriate directory in your RGLUnityPlugin.
  3. Copy all ROS2 libraries from <build-dir>/ros2_standalone/ to Ros2ForUnity\Plugins\Windows\x86_64 directory. Skip for duplicates.

RGL's ROS2 standalone build is dependent on ROS2ForUnity's ROS2 standalone build. RobotecGPULidar library will find ROS2 because ROS2ForUnity sets the environment variable Path for the ROS2 libraries.

Usage

Each RGL node for ROS2 publishing must be connected to a format node that defines fields and their layout in the binary data. For example, to publish PointCloud2 message with fields XYZ and DISTANCE, the code should look as follow:

...
rgl_node_t nodeFormat = nullptr, nodeRos2 = nullptr;
std::vector<rgl_field_t> fieldsToPublish = { RGL_FIELD_XYZ_VEC3_F32, RGL_FIELD_DISTANCE_F32 };
rgl_node_points_format(&nodeFormat, fieldsToPublish.data(), fieldsToPublish.size())
rgl_node_points_ros2_publish(&nodeRos2, "example_topic", "example_frame");

rgl_graph_node_add_child(..., nodeFormat);
rgl_graph_node_add_child(nodeFormat, nodeRos2);

API documentation

More details can be found here.