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Note: This tutorial assumes that you have completed the previous tutorials: ExtractPolygonalPrismData segmentation.
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ExtractPolygonalPrismData segmentation

Description: ExtractPolygonalPrismData segmentation

Tutorial Level:

Contents

The following launch file starts a nodelet manager together with a VoxelGrid PCL filter nodelet. The input PointCloud2 topic is set to /scene_pointcloud2.

The default filtering values are set to filter data on the z-axis between 0.01 and 1.5 meters, and downsample the data with a leaf size of 0.01 meters.

The segmentation is performed by first estimating surface normals at each point for a support of 0.015 meters, and then using a RANSAC-based estimator for fitting planes with a threshold of 0.1 meters, and a normal deviation of ~5 degrees (0.09 radians).

The convex hull of the projected planar inliers is estimated and an ExtractPolygonalPrismData nodelet is used to extract all point indices between 0 and 0.5 meters from the planar table support, with their projections falling inside the convex hull.

   1 <launch>
   2   <node pkg="nodelet" type="nodelet" name="pcl_manager" args="manager" output="screen" />
   3 
   4   <!-- Run a VoxelGrid filter to clean NaNs and downsample the data -->
   5   <node pkg="nodelet" type="nodelet" name="voxel_grid" args="load pcl/VoxelGrid pcl_manager" output="screen">
   6     <remap from="~input" to="/scene_pointcloud2" />
   7     <rosparam>
   8       filter_field_name: z
   9       filter_limit_min: 0.01
  10       filter_limit_max: 1.5
  11       filter_limit_negative: False
  12       leaf_size: 0.01
  13     </rosparam>
  14   </node>
  15 
  16   <!-- Estimate point normals -->
  17   <node pkg="nodelet" type="nodelet" name="normal_estimation" args="load pcl/NormalEstimation pcl_manager" output="screen">
  18     <remap from="~input" to="/voxel_grid/output" />
  19     <rosparam>
  20       # -[ Mandatory parameters
  21       k_search: 0
  22       radius_search: 0.015
  23       # Set the spatial locator. Possible values are: 0 (ANN), 1 (FLANN), 2 (organized)
  24       spatial_locator: 0
  25     </rosparam>
  26   </node>
  27 
  28   <!-- Segment the table plane -->
  29   <node pkg="nodelet" type="nodelet" name="planar_segmentation" args="load pcl/SACSegmentationFromNormals pcl_manager" output="screen">
  30     <remap from="~input"   to="/voxel_grid/output" />
  31     <remap from="~normals" to="/normal_estimation/output" />
  32     <rosparam>
  33       # -[ Mandatory parameters
  34       model_type: 11
  35       distance_threshold: 0.1
  36       max_iterations: 1000
  37       method_type: 0
  38       optimize_coefficients: true
  39       normal_distance_weight: 0.1
  40       eps_angle: 0.09
  41     </rosparam>
  42   </node>
  43 
  44   <node pkg="nodelet" type="nodelet" name="extract_plane_indices" args="load pcl/ExtractIndices pcl_manager" output="screen">
  45     <remap from="~input"   to="/voxel_grid/output" />
  46     <remap from="~indices" to="/planar_segmentation/inliers" />
  47     <rosparam>
  48       negative: true
  49     </rosparam>
  50   </node>
  51 
  52   <!-- Project the planar inliers -->
  53   <node pkg="nodelet" type="nodelet" name="project_plane_inliers" args="load pcl/ProjectInliers pcl_manager" output="screen">
  54    <remap from="~input"   to="/voxel_grid/output" />
  55    <remap from="~indices" to="/planar_segmentation/inliers" />
  56    <remap from="~model"   to="/planar_segmentation/model" />
  57    <rosparam>
  58      model_type: 11
  59      copy_all_data: false
  60      copy_all_fields: true
  61    </rosparam>
  62   </node>
  63 
  64   <!-- Compute the convex hull -->
  65   <node pkg="nodelet" type="nodelet" name="convex_hull" args="load pcl/ConvexHull2D pcl_manager" output="screen">
  66     <remap from="~input"   to="/project_plane_inliers/output" />
  67   </node>
  68 
  69   <!-- Extract the object clusters using a polygonal prism -->
  70   <node pkg="nodelet" type="nodelet" name="extract_objects_table" args="load pcl/ExtractPolygonalPrismData pcl_manager" output="screen">
  71    <remap from="~input"         to="/extract_plane_indices/output" />
  72    <remap from="~planar_hull"   to="/convex_hull/output" />
  73    <rosparam>
  74      height_min: 0
  75      height_max: 0.5
  76    </rosparam>
  77   </node>
  78 
  79   <node pkg="nodelet" type="nodelet" name="extract_objects_indices" args="load pcl/ExtractIndices pcl_manager" output="screen">
  80     <!-- Extract_plane_indices needs to be negated for this work -->
  81     <remap from="~input"   to="/extract_plane_indices/output" />
  82     <remap from="~indices" to="/extract_objects_table/output" />
  83     <rosparam>
  84       negative: false
  85     </rosparam>
  86   </node>
  87 </launch>


2019-10-19 12:59