Removing points from a pcl::PointCloud

Question

I'm new in PCL. I'm using the PCL library and I'm looking for a way to extract points from a point cloud or copying particular points to a new one. I want to verify for each point if it respects a condition and I want to obtain a point cloud with only the good points.Thank you!

Answer 1

Use the ExtractIndices class:

• add your points to be removed to a PointIndices variable
• pass these Indices to the ExtractIndices
• run filter() method "negatively" to get the original cloud minus your points

example:

  pcl::PointCloud<pcl::PointXYZ>::Ptr p_obstacles(new pcl::PointCloud<pcl::PointXYZ>);
  pcl::PointIndices::Ptr inliers(new pcl::PointIndices());
  pcl::ExtractIndices<pcl::PointXYZ> extract;
  for (int i = 0; i < (*p_obstacles).size(); i++)
  {
    pcl::PointXYZ pt(p_obstacles->points[i].x, p_obstacles->points[i].y, p_obstacles->points[i].z);
    float zAvg = 0.5f;
    if (abs(pt.z - zAvg) < THRESHOLD) // e.g. remove all pts below zAvg
    {
      inliers->indices.push_back(i);
    }
  }
  extract.setInputCloud(p_obstacles);
  extract.setIndices(inliers);
  extract.setNegative(true);
  extract.filter(*p_obstacles);

Answer 2

If you are new to PCL. It should be a good idea to take a look at at the documentation:

http://pointclouds.org/documentation/tutorials/

I think that what you are looking for is explained in this tutorial:

http://pointclouds.org/documentation/tutorials/remove_outliers.php#remove-outliers

Try to reproduce the example on your machine and then modify it to fit your needs.