介绍
“Clustering of Pointclouds into Supervoxels” 是一种点云数据聚类的方法,用于将点云数据分割成具有相似特征的超体素(supervoxel)。
超体素是一种在点云数据中表示连续区域的方法,类似于像素在图像中表示连续区域。超体素是点云数据的小块区域,具有相似的几何特征和颜色特征。通过将点云数据聚类成超体素,可以实现对点云数据的语义分割和对象识别。
“Clustering of Pointclouds into Supervoxels” 方法的主要步骤如下:
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首先,对输入的点云数据进行预处理,包括点云滤波、法线估计等操作,以获取点云的几何和颜色特征。
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然后,通过选择一个种子点(seed point)开始,使用一种聚类算法(如欧几里得聚类或基于图的聚类)将点云数据分割成超体素。聚类过程中,会考虑点云的几何和颜色特征,以确保超体素内的点具有相似的特征。
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聚类过程中,可以根据一些准则(如紧密度、颜色一致性等)对超体素进行合并或分割,以进一步优化聚类结果。
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最后,生成的超体素可以用于点云的语义分割、对象识别等应用。可以根据超体素的特征,将点云数据划分为不同的对象或区域。
“Clustering of Pointclouds into Supervoxels” 方法在点云处理和分析中具有广泛的应用,特别是在三维场景理解、目标检测和机器人导航等领域。通过将点云数据聚类为超体素,可以提取出具有语义信息的局部区域,为后续的处理和分析提供更准确和可靠的数据基础。
效果
代码
#include <pcl/console/parse.h>
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>
#include <pcl/io/pcd_io.h>
#include <pcl/visualization/pcl_visualizer.h>
#include <pcl/segmentation/supervoxel_clustering.h>//VTK include needed for drawing graph lines
#include <vtkPolyLine.h>// Types
typedef pcl::PointXYZRGBA PointT;
typedef pcl::PointCloud<PointT> PointCloudT;
typedef pcl::PointNormal PointNT;
typedef pcl::PointCloud<PointNT> PointNCloudT;
typedef pcl::PointXYZL PointLT;
typedef pcl::PointCloud<PointLT> PointLCloudT;void addSupervoxelConnectionsToViewer (PointT &supervoxel_center,PointCloudT &adjacent_supervoxel_centers,std::string supervoxel_name,pcl::visualization::PCLVisualizer::Ptr & viewer);int main (int argc, char ** argv)
{if (argc < 2){pcl::console::print_error ("Syntax is: %s <pcd-file> \n ""--NT Dsables the single cloud transform \n""-v <voxel resolution>\n-s <seed resolution>\n""-c <color weight> \n-z <spatial weight> \n""-n <normal_weight>\n", argv[0]);return (1);}PointCloudT::Ptr cloud (new PointCloudT);pcl::console::print_highlight ("Loading point cloud...\n");if (pcl::io::loadPCDFile<PointT> (argv[1], *cloud)){pcl::console::print_error ("Error loading cloud file!\n");return (1);}bool disable_transform = pcl::console::find_switch (argc, argv, "--NT");float voxel_resolution = 0.008f;// 用于体素化点云数据的分辨率bool voxel_res_specified = pcl::console::find_switch (argc, argv, "-v");if (voxel_res_specified)pcl::console::parse (argc, argv, "-v", voxel_resolution);float seed_resolution = 0.1f; // 用于种子点选择的分辨率bool seed_res_specified = pcl::console::find_switch (argc, argv, "-s");if (seed_res_specified)pcl::console::parse (argc, argv, "-s", seed_resolution);float color_importance = 0.2f;if (pcl::console::find_switch (argc, argv, "-c"))pcl::console::parse (argc, argv, "-c", color_importance);float spatial_importance = 0.4f;if (pcl::console::find_switch (argc, argv, "-z"))pcl::console::parse (argc, argv, "-z", spatial_importance);float normal_importance = 1.0f;if (pcl::console::find_switch (argc, argv, "-n"))pcl::console::parse (argc, argv, "-n", normal_importance);// //// This is how to use supervoxels// //pcl::SupervoxelClustering<PointT> super (voxel_resolution, seed_resolution);if (disable_transform)super.setUseSingleCameraTransform (false);super.setInputCloud (cloud);super.setColorImportance (color_importance); // 设置颜色重要性super.setSpatialImportance (spatial_importance); // 设置空间重要性super.setNormalImportance (normal_importance); // 设置法线重要性std::map <std::uint32_t, pcl::Supervoxel<PointT>::Ptr > supervoxel_clusters;pcl::console::print_highlight ("Extracting supervoxels!\n");super.extract (supervoxel_clusters);pcl::console::print_info ("Found %d supervoxels\n", supervoxel_clusters.size ());pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));viewer->setBackgroundColor (0, 0, 0);PointCloudT::Ptr voxel_centroid_cloud = super.getVoxelCentroidCloud (); // 获取超体素的体素质心点云viewer->addPointCloud (voxel_centroid_cloud, "voxel centroids");viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE,2.0, "voxel centroids");viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_OPACITY,0.95, "voxel centroids");PointLCloudT::Ptr labeled_voxel_cloud = super.getLabeledVoxelCloud (); // 获取标记过的点云viewer->addPointCloud (labeled_voxel_cloud, "labeled voxels");viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_OPACITY,0.8, "labeled voxels");PointNCloudT::Ptr sv_normal_cloud = super.makeSupervoxelNormalCloud (supervoxel_clusters); //获取超体素的法线点云//We have this disabled so graph is easy to see, uncomment to see supervoxel normals//viewer->addPointCloudNormals<PointNormal> (sv_normal_cloud,1,0.05f, "supervoxel_normals");pcl::console::print_highlight ("Getting supervoxel adjacency\n");std::multimap<std::uint32_t, std::uint32_t> supervoxel_adjacency;super.getSupervoxelAdjacency (supervoxel_adjacency); // 获取超体素的邻接关系//To make a graph of the supervoxel adjacency, we need to iterate through the supervoxel adjacency multimapor (auto label_itr = supervoxel_adjacency.cbegin (); label_itr != supervoxel_adjacency.cend (); ){//First get the labelstd::uint32_t supervoxel_label = label_itr->first;//Now get the supervoxel corresponding to the labelpcl::Supervoxel<PointT>::Ptr supervoxel = supervoxel_clusters.at (supervoxel_label);//Now we need to iterate through the adjacent supervoxels and make a point cloud of themPointCloudT adjacent_supervoxel_centers;for (auto adjacent_itr = supervoxel_adjacency.equal_range (supervoxel_label).first; adjacent_itr!=supervoxel_adjacency.equal_range (supervoxel_label).second; ++adjacent_itr){pcl::Supervoxel<PointT>::Ptr neighbor_supervoxel = supervoxel_clusters.at (adjacent_itr->second);adjacent_supervoxel_centers.push_back (neighbor_supervoxel->centroid_);}//Now we make a name for this polygonstd::stringstream ss;ss << "supervoxel_" << supervoxel_label;//This function is shown below, but is beyond the scope of this tutorial - basically it just generates a "star" polygon mesh from the points givenaddSupervoxelConnectionsToViewer (supervoxel->centroid_, adjacent_supervoxel_centers, ss.str (), viewer);//Move iterator forward to next labellabel_itr = supervoxel_adjacency.upper_bound (supervoxel_label);}while (!viewer->wasStopped ()){viewer->spinOnce (100);}return (0);}void addSupervoxelConnectionsToViewer (PointT &supervoxel_center,PointCloudT &adjacent_supervoxel_centers,std::string supervoxel_name,pcl::visualization::PCLVisualizer::Ptr & viewer){vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New ();vtkSmartPointer<vtkCellArray> cells = vtkSmartPointer<vtkCellArray>::New ();vtkSmartPointer<vtkPolyLine> polyLine = vtkSmartPointer<vtkPolyLine>::New ();//Iterate through all adjacent points, and add a center point to adjacent point pairfor (auto adjacent_itr = adjacent_supervoxel_centers.begin (); adjacent_itr != adjacent_supervoxel_centers.end (); ++adjacent_itr){points->InsertNextPoint (supervoxel_center.data);points->InsertNextPoint (adjacent_itr->data);}// Create a polydata to store everything invtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New ();// Add the points to the datasetpolyData->SetPoints (points);polyLine->GetPointIds ()->SetNumberOfIds(points->GetNumberOfPoints ());for(unsigned int i = 0; i < points->GetNumberOfPoints (); i++)polyLine->GetPointIds ()->SetId (i,i);cells->InsertNextCell (polyLine);// Add the lines to the datasetpolyData->SetLines (cells);viewer->addModelFromPolyData (polyData,supervoxel_name);}