octomap_ros

Python binding of the OctoMap library for ROS (Robot Operating System).

Installation

ROS Humble Integration

To use OctoMap with ROS Humble, install the following ROS packages:

sudo apt-get install ros-humble-octomap ros-humble-octomap-mapping ros-humble-octomap-server

These packages provide the necessary ROS integration for OctoMap:

• ros-humble-octomap: Core OctoMap library for ROS
• ros-humble-octomap-mapping: Provides mapping capabilities using OctoMap
• ros-humble-octomap-server: Offers a ROS server for OctoMap, allowing you to save, load, and publish OctoMaps

Python Package

Install octomap_ros directly from PyPI:

pip install octomap-ros

Prerequisites:

• Python development headers: sudo apt-get install python3-dev
• C++ compiler: sudo apt-get install build-essential
• CMake: sudo apt-get install cmake

Difference from Other Packages

The key difference between octomap_ros and other packages is that it provides the capability to convert OctoMap messages in ROS to OctoMap OcTrees. This is crucial for ROS 2 users, as the existing octomap_msgs has not been fully ported over to ROS 2, leaving a gap in functionality. octomap_ros fills this void, allowing ROS 2 users to directly work with OctoMap data in the form of OcTrees, which is essential for most mapping and occupancy grid operations.

ROS Humble Usage

Here's a basic example of how to use OctoMap with ROS Humble:

import rclpy
from rclpy.node import Node
from octomap_msgs.msg import Octomap
import octomap
import numpy as np

class OctomapProcessor(Node):
    def __init__(self):
        super().__init__('octomap_processor')
        self.subscription = self.create_subscription(
            Octomap,
            '/octomap_binary',
            self.octomap_callback,
            10)
        self.octree = octomap.OcTree(0.1)  # 0.1 is the resolution

    def octomap_callback(self, msg):
        # Convert ROS message to OcTree using binaryMsgToMap
        tree = octomap.OcTree.binaryMsgToMap(msg.resolution, 
                                             msg.id.encode('utf-8'), 
                                             msg.binary, 
                                             msg.data)
    
        if tree is None:
            self.get_logger().warn("Failed to create OcTree from message")
            return
    
        # Process the OcTree
        for node in tree.begin_tree():
            if tree.isNodeOccupied(node):
                # Process occupied nodes
                coord = node.getCoordinate()
                self.get_logger().info(f"Occupied node at {coord[0]}, {coord[1]}, {coord[2]}")

        # You can also update your own OcTree
        occupied_points, _ = tree.extractPointCloud()
        if len(occupied_points) > 0:
            self.octree.insertPointCloud(
                occupied_points,
                np.array([0.0, 0.0, 0.0])  # origin
            )
    
        self.get_logger().info(f"Updated OcTree, now has {self.octree.size()} nodes")

def main(args=None):
    rclpy.init(args=args)
    octomap_processor = OctomapProcessor()
    rclpy.spin(octomap_processor)
    octomap_processor.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

This example demonstrates how to:

1. Subscribe to the /octomap_binary topic
2. Process incoming OctoMap messages
3. Convert ROS messages to OcTree objects
4. Iterate through occupied nodes in the OcTree
5. Update a local OcTree with new data

To run the OctoMap server and visualize the data:

# Run the octomap server
ros2 run octomap_server octomap_server_node

# In another terminal, run your OctoMap processor
python3 your_octomap_processor.py

# View the OctoMap in RViz
ros2 run rviz2 rviz2

Configure RViz to display the OctoMap by adding an OccupancyGrid or MarkerArray display and setting the appropriate topic (usually /octomap_binary or /octomap_full).

Acknowledgement

This package is based on wkentaro/octomap-python and neka-nat/python-octomap, adapted for ROS integration.

License

octomap_ros is licensed under the BSD License. See the LICENSE file for details.