如何使用PCL提取点云数据中的一组点？

Question

我有一个点云数据，通过点击一个点，我想提取半径范围内点击点周围的点。我还想将提取的点推送到新的云中。使用 Pointpikindingevent，我可以单击一个点并将其推送到云中。如何提取一组点，比如从单击点开始围绕 0.02 厘米半径的点并将它们推入新云中？

Answer 1

给定一个点云：

pcl::PointCloud<pcl::PointXYZ>::Ptr cloud

然后生成一个Kdtree来进行高效的范围搜索：

pcl::KdTreeFLANN<pcl::PointXYZ> kdtree;
kdtree.setInputCloud (cloud);

然后，给定一个点和一个半径：

pcl::PointXYZ searchPoint(1,2,3);
float radius = 4;

您可以得到距离点 searchPoint:

距离 radius 的所有点

std::vector<int> pointIdxRadiusSearch; //to store index of surrounding points 
std::vector<float> pointRadiusSquaredDistance; // to store distance to surrounding points

if ( kdtree.radiusSearch (searchPoint, radius, pointIdxRadiusSearch, pointRadiusSquaredDistance) > 0 )
{
    for (size_t i = 0; i < pointIdxRadiusSearch.size (); ++i)
        std::cout << "    "  <<   cloud->points[ pointIdxRadiusSearch[i] ].x 
                << " " << cloud->points[ pointIdxRadiusSearch[i] ].y 
                << " " << cloud->points[ pointIdxRadiusSearch[i] ].z 
                << " (squared distance: " << pointRadiusSquaredDistance[i] << ")" << std::endl;
}

您可以打印所有周围的点及其到 searchPoint 的距离以检查代码功能的正确性。

最后，用获得的点创建一个云：

pcl::PointCloud<pcl::PointXYZ>::Ptr cloud_cluster (new pcl::PointCloud<pcl::PointXYZ>);
for (size_t i = 0; i < pointIdxRadiusSearch.size (); ++i)
    cloud_cluster->points.push_back(cloud->points[ pointIdxRadiusSearch[i] ]);
cloud_cluster->width = cloud_cluster->points.size ();
cloud_cluster->height = 1;
cloud_cluster->is_dense = true;

Answer 2

为了能够选择一个点，您可以使用类似于 this answer 的 PointPickingEvent。

你的.h中的Class声明，

class PCLViewer : public QMainWindow
{
  Q_OBJECT

public:
  explicit PCLViewer (QWidget *parent = 0);
  ~PCLViewer ();
    void pointPickCallback (const pcl::visualization::PointPickingEvent& event, void*);

public slots:

protected:
  boost::shared_ptr<pcl::visualization::PCLVisualizer> viewer;
  pcl::PointCloud<pcl::PointXYZRGB>::Ptr cloud;
  pcl::PointXYZ src_point_;
  bool src_point_selected_;

private:
  Ui::PCLViewer *ui;

};

在你的 .cpp 中，

PCLViewer::PCLViewer (QWidget *parent) :
  QMainWindow (parent),
  ui (new Ui::PCLViewer)
{
    ui->setupUi (this);

    [...]

    viewer.reset (new pcl::visualization::PCLVisualizer ("viewer", false));
    viewer->registerPointPickingCallback (&PCLViewer::pointPickCallback, *this);

    [...]
}

和附加功能，

void
PCLViewer::pointPickCallback (const pcl::visualization::PointPickingEvent& event, void*)
{
  // Check to see if we got a valid point. Early exit.
  int idx = event.getPointIndex ();
  if (idx == -1)
    return;

  // Get the point that was picked
  event.getPoint (src_point_.x, src_point_.y, src_point_.z);
  PCL_INFO ("Src Window: Clicked point %d with X:%f Y:%f Z:%f\n", idx, src_point_.x, src_point_.y, src_point_.z);
  src_point_selected_ = true;
}

在手动注册应用程序中有更详细的使用示例： pcl/apps/src/manual_registration/manual_registration.cpp pcl/apps/include/pcl/apps/manual_registration.h

如何使用PCL提取点云数据中的一组点？

How to extract a set of points in a point cloud data using PCL?

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