README

ROS2 specific libraries and utilities

cloudini_topic_converter

A simple node that subscribes to one of these two topic types and publishes the other:

  • sensor_msgs/msg/PointCloud2

  • point_cloud_interfaces/msg/CompressedPointCloud2

It is genrally more efficient than using the point_cloud_transport because the latter would:

  1. Receive a serialized DDS message.

  2. Convert that to CompressedPointCloud2.

  3. Do the actual decompression.

  4. Convert PointCloud2 to a serialized DDS message.

Instead, we work directly with raw serialized messages, bypassing the ROS type system, skipping steps 2 and 4 in the list above.

Parameters

  • topic_input (string): name of the topic to subscribe to.

  • topic_output (string): name of the topic to publish into.

  • compressing(bool): true if you are subscribing to a regular pointcloud2, and you want to compress it. False if you are subscribing to a compressed topic and you want to decompress it.

  • resolution (double): resolution of floating point fields in meters. Default: 0.001

Example usage

To convert a regular sensor_msgs/msg/PointCloud2 to a compressed one:

ros2 run cloudini_ros cloudini_topic_converter --ros-args \
    -p compressing:=true  \
    -p topic_input:=/points  \
    -p topic_output:=/points/compressed

To decompress that topic back in to its original form:

ros2 run cloudini_ros cloudini_topic_converter --ros-args \
    -p compressing:=false  \
    -p topic_input:=/points/compressed  \
    -p topic_output:=/points/decompressed

cloudini_rosbag_converter

A command line tool that, given a rosbag (limited to MCAP format), converts all sensor_msgs/msg/PointCloud2 topics into compressed point_cloud_interfaces/msg/CompressedPointCloud2 of vice-versa.

Encoding/decoding is faster than general-purpose compression algorithms and achieves a better compression ratio at 1mm resolution.

Interestingly, it can be compiled without ROS installed in your system!

Example usage: round trip compression / decompression;

# Use option -c for compression
cloudini_rosbag_converter -f original_rosbag.mcap -o compressed_rosbag.mcap -c

# Use option -d for decompression
cloudini_rosbag_converter -f compressed_rosbag.mcap -o restored_rosbag.mcap -d

Note that the “restored_rosbag.mcap” might be smaller than the original one, because the chunk-based ZSTD compression provided by MCAP is enabled.

How to read directly a CompressedPointCloud2 from your application

Using the point_cloud_transport plugin

You can see a practical example in test/test_plugin_publisher.cpp and test/test_plugin_subscriber.cpp

Use CloudiniSubscriberPCL (when using PCL)

A special subscriber is provided to subscribe to a topic with type point_cloud_interfaces/msg/CompressedPointCloud2 and convert its content to pcl::PointCloud2 automatically.

See example test/test_cloudini_subscriber.cpp

Alternaively, you can use the code as a template to see how convertion is implemented and crate your own version.

Example:

  1. Publish a regular pointcloud from a rosbag:

# Assuming that this rosbag contains a topic called "/points"
ros2 bag play -l my_rosbag/

  1. Run topic_converter as mentioned above to create a topic called “/points/compressed”:

ros2 run cloudini_ros cloudini_topic_converter --ros-args \
    -p compressing:=true  \
    -p topic_input:=/points  \
    -p topic_output:=/points/compressed

  1. Subscribe using test_cloudini_subscriber:

ros2 run cloudini_ros test_cloudini_subscriber --ros-args -p topic:=/points/compressed