<POINT CLOUD TRANSPORT TUTORIAL>

ROS2 v0.1.

Contents

• Writing a Simple Publisher
  • Code of the Publisher
  • Code Explained
  • Example of Running the Publisher
• Writing a Simple Subscriber
  • Code of the Subscriber
  • Code Explained
  • Example of Running the Subscriber
• Using Publishers And Subscribers With Plugins
  • Running the Publisher and Subsriber
  • Changing the Transport Used
  • Changing Transport Behavior
• Implementing Custom Plugins

Writing a Simple Publisher

In this section, we’ll see how to create a publisher node, which opens a ROS 2 bag and publishes PointCloud2 messages from it.

This tutorial assumes that you have created your workspace containing [](https://github.com/ros-perception/point_cloud_transport) and [](https://github.com/ros-perception/point_cloud_transport_plugins)

Before we start, change to the directory, clone this repository, and unzip the example rosbag in the resources folder:

$ cd ~/<point_cloud_transport_ws>/src
$ git clone https://github.com/ros-perception/point_cloud_transport_tutorial
$ cd point_cloud_transport_tutorial
$ tar -C resources/ -xvf resources/rosbag2_2023_08_05-16_08_51.tar.xz
$ cd ~/<point_cloud_transport_ws>
$ colcon build --merge-install --event-handlers console_direct+

Code of the Publisher

Take a look at my_publisher.cpp

```cpp #include #include #include #include #include

// for reading rosbag #include <ament_index_cpp/get_package_share_path.hpp>

#include <point_cloud_transport/point_cloud_transport.hpp> #include <rclcpp/executors/single_threaded_executor.hpp> #include <rclcpp/node.hpp> #include <rclcpp/serialization.hpp> #include <rclcpp/serialized_message.hpp> #include <rclcpp/utilities.hpp> #include <rosbag2_cpp/reader.hpp> #include <rosbag2_storage/storage_options.hpp> #include <rosbag2_cpp/converter_options.hpp> #include <sensor_msgs/msg/point_cloud2.hpp>

int main(int argc, char ** argv) { rclcpp::init(argc, argv);

auto node = std::make_shared<rclcpp::Node>(“point_cloud_publisher”);

rclcpp::executors::SingleThreadedExecutor executor; executor.add_node(node);

point_cloud_transport::PointCloudTransport pct(*node); point_cloud_transport::Publisher pub = pct.advertise(“pct/point_cloud”, 100);

const std::string bagged_cloud_topic = “/point_cloud”; std::filesystem::path bag_file = ament_index_cpp::get_package_share_path(“point_cloud_transport_tutorial”) / “resources” / “rosbag2_2023_08_05-16_08_51”;

if (argc > 1) { bag_file = std::filesystem::path(argv[1]); }

if (!std::filesystem::exists(bag_file)) { std::cout « “Not able to open file [” « bag_file.string() « ”]” « ‘\n’; return -1; }

std::cout « “Reading [” « bag_file.string() « ”] bagfile” « ‘\n’;

// boiler-plate to tell rosbag2 how to read our bag rosbag2_storage::StorageOptions storage_options; storage_options.uri = bag_file.string(); storage_options.storage_id = “mcap”; rosbag2_cpp::ConverterOptions converter_options; converter_options.input_serialization_format = “cdr”; converter_options.output_serialization_format = “cdr”;

// open the rosbag rosbag2_cpp::readers::SequentialReader reader; reader.open(storage_options, converter_options);

sensor_msgs::msg::PointCloud2 cloud_msg; rclcpp::Serialization<sensor_msgs::msg::PointCloud2> cloud_serialization; while (reader.has_next() && rclcpp::ok()) {

File truncated at 100 lines see the full file

Any contribution that you make to this repository will be under the 3-Clause BSD License, as dictated by that license.