VTK/Examples/Cxx/DataStructures/KdTreePointLocator/ClosestNPoints

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkPointSource.h>
#include <vtkPolyData.h>
#include <vtkCellArray.h>
#include <vtkIdList.h>
#include <vtkKdTreePointLocator.h>
 
int main(int, char *[])
{
  //Create some random points
  vtkSmartPointer<vtkPointSource> pointSource = 
      vtkSmartPointer<vtkPointSource>::New();
  pointSource->SetNumberOfPoints(10);
  pointSource->Update();
 
  //Create the tree
  vtkSmartPointer<vtkKdTreePointLocator> pointTree = 
      vtkSmartPointer<vtkKdTreePointLocator>::New();
  pointTree->SetDataSet(pointSource->GetOutput());
  pointTree->BuildLocator();
 
  // Find the k closest points to (0,0,0)
  unsigned int k = 1;
  double testPoint[3] = {0.0, 0.0, 0.0};
  vtkSmartPointer<vtkIdList> result = 
      vtkSmartPointer<vtkIdList>::New();
 
  pointTree->FindClosestNPoints(k, testPoint, result);
 
  for(vtkIdType i = 0; i < k; i++)
    {
    vtkIdType point_ind = result->GetId(i);
    double p[3];
    pointSource->GetOutput()->GetPoint(point_ind, p);
    std::cout << "Closest point " << i << ": Point "
      << point_ind << ": (" << p[0] << ", " << p[1] << ", " << p[2] << ")" << std::endl;
    }
 
  return EXIT_SUCCESS;
}