points_from_volume Documentation

Author:

Joel Pereira

points_from_volume: convexhull

convexhull

Homepage: http://ros.org/wiki/convexhull

points_from_volume is a package that includes points_from_volume library

The points_from_volume library extracts points from the inside/outside of a polygon.

Usage

How to use?

Class declaration

On the code do:

// The input pcl could be either a PointXYZ or a PointXYZRGB
points_from_volume<pcl::PointXYZ> pfv;

Definition of parameters (Mandatory)

// After the ROS initialization you must declare 3 parameters
ros::init(argc, argv, "points_from_volume_nodelet"); 
ros::NodeHandle n("~"); 
p_n=&n;
// Positive offset of the convexhull
n.param("positive_offset", positive, 2.0);
// Negative ofset of the convexhull
n.param("negative_offset", negative, -0.1);
// Flag that defines is you are searching for points inside(flag=false) or outside (flag=true) the convexhull
n.param("flag_in_out", flag, false);

ROS subscription

// You need to subscribe 2 point clouds. 
// The first one contains the points needed to define the convexhull
ros::Subscriber sub1 = n.subscribe ("/points_convexhull", 1, cb_points_convexhull);
// The second one is the point cloud with the points to filter
ros::Subscriber sub2 = n.subscribe ("/point_cloud_input", 1, cloud_cb);  

Callbaks

// The first callbak (cb_points_convexhull) needs to call a function from the points_from_volume class to set the convexhull
pfv.set_convex_hull(pcmsg_convexhull_in);

// The second callbak (cloud_cb) sets the convexhull solid... 
pfv.convexhull_function(pc_in, positive, negative, flag);
// And then you can return the filtered point cloud             
pfv.get_pc_in_volume();

Publish the point cloud

ros::Publisher = n.advertise<sensor_msgs::PointCloud2>("/pcmsg_out", 1); // Where /pcmsg_out is the name of the publisher

The example nodelet

Example of a xml launch file for a point cloud received from a Kinect sensor

<launch>
  <node name="openni_node" pkg="openni_camera" type="openni_node" />    
  <node name="points_from_volume_nodelet" pkg="points_from_volume" type="points_from_volume_nodelet" args="point_cloud_input:=/camera/depth/points"/>
  <!-- Setting parameters -->
    <param  name= "positive_offset" type="float"  value="2.0" />  
    <param  name= "negative_offset" type="float" value="-0.1" /> 
    <param  name= "flag_in_out" type="bool" value="false" />
  <!-- !!!You need to publish your convexhull points too!!! -->   
</launch>