Point Cloud Generator

Generate ROS2 PointCloud2 messages from the PointCloudSoup messages published by Hammerhead.

Overview

This example demonstrates how to subscribe to bandwidth-efficient PointCloudSoup messages and convert them to standard sensor_msgs/PointCloud2 messages for visualization and processing. The point clouds that Hammerhead generates can overwhelm the network due to bandwidth requirements. PointCloudSoup messages provide a compressed representation that can be losslessly reconstructed into XYZRGB point clouds while using a fraction of the bandwidth.

Build

cd hammerhead_ros2
colcon build --packages-up-to point_cloud_generator_py

Prerequisites

Configure Hammerhead to publish PointCloudSoup messages by modifying master_config.ini:

publish_point_cloud_type = 5

Usage

# Source the workspace
source install/setup.bash

# Run the point cloud generator
ros2 run point_cloud_generator_py point_cloud_generator_py

Features

  • Bandwidth Optimization: Converts compressed PointCloudSoup messages to standard PointCloud2
  • Downsampling: Reduces point cloud density by factor of 10 for network efficiency
  • Real-time Processing: Publishes reconstructed point clouds in real-time
  • Quality of Service: Uses BEST_EFFORT QoS policy for optimal performance

Topic Interface

Subscribed Topics

  • /nodar/point_cloud_soup - Compressed point cloud data from Hammerhead

Published Topics

  • /nodar/point_cloud - Standard ROS2 point cloud messages (sensor_msgs/PointCloud2)

Important rviz2 Configuration

This example publishes point clouds with ReliabilityPolicy.BEST_EFFORT QoS policy. In rviz2:

  1. Add a PointCloud2 display
  2. Set topic to /nodar/point_cloud
  3. Change Reliability Policy to Best Effort

Performance Tuning

ROS2 DDS Configuration

If you are having networking issues, please refer to the ROS2 DDS tuning guide. For example, you may want to modify the fragmentation settings: 

# Adjust IP fragmentation settings
sudo sysctl net.ipv4.ipfrag_time=3
sudo sysctl net.ipv4.ipfrag_high_thresh=536870912

Production Considerations

  • Bandwidth: Monitor network usage when publishing PointCloud2 messages
  • Downsampling: Current example downsamples by factor of 10 - adjust as needed
  • QoS Settings: Consider appropriate QoS policies for your application

Troubleshooting

  • No point clouds visible: Verify Hammerhead is publishing PointCloudSoup messages
  • Poor performance: Check network configuration and DDS settings
  • rviz2 display issues: Ensure Reliability Policy is set to Best Effort
  • Memory issues: Consider using C++ version for high-performance applications