This package provides an implementation of object and surface extraction from a point cloud using the Point Cloud Library (pcl_ros). It is based on the Euclidean Cluster Extraction tutorial on pcl.org.

Facilities for extracting objects, measuring their apparent size, distance from the coordinate frame origin, and color, and filtering by these attributes are provided. In addition, this package also provides facilities for discovering surfaces and filtering out those which do not appear level with respect to the x-y plane. See the Code API for more information about these and how to use them.

For convenience, a ROS service and a handful of command line tools are provided.

Example

Given the example input point cloud captured with a Microsoft Kinect:

The following objects are discovered, filtering by objects with a minimum bounding sphere radius in [3cm, 5cm]:

And the following level planes are discovered:

Your mileage may vary. See the Code API for parameters that can be tuned for best results.

Services

Object Extraction - provided by extract_objects_srv

This service provides a convenient implementation of object and surface discovery in accordance with ExtractObjects.srv. A caller may specify the minimum and maximum acceptable bounding sphere radii and the minimum and maximum acceptable distances from the origin for discovered objects, as well as the acceptable tolerance for determining whether a surface is level. Given a sensor_msgs/PointCloud2 to process, the satisfactory objects and surfaces are returned.

Nodes

extract_objects_srv

Provides an implementation of ExtractObjects.srv using the object/surface discovery and filtering primitives provided by this package.

This service always assumes the name "extract_objects" in ROS.

Parameters

No parameters are accepted at this time.

Command-line Tools

extract_objects

This tool extracts objects from a given .pcd point cloud file and saves the resulting objects as "object_*.pcd" with unique numbers in the current working directory. Run the tool with no arguments for additional usage information.

extract_objects_rgb

This tool provides the same functionality as extract_objects, but preserves RGB information if it is available in the given input .pcd file.

measure_objects

Given one or more .pcd point clouds to process, this tool prints out:

• The number of points in each given point cloud
• The centroid of each given point cloud, as (x, y, z)
• The minimum bounding sphere radius of each given point cloud

measure_objects_rgb

This tool provides the same functionality as measure_objects, but for point clouds with RGB color information available.

In addition to the information printed by measure_objects, measure_objects_rgb also produces:

• The average hue of all points in each given point cloud