VTK/Examples/Cxx/DataStructures/OctreeFindPointsWithinRadius

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkPointSource.h>
#include <vtkPolyData.h>
#include <vtkCellArray.h>
#include <vtkIdList.h>
#include <vtkOctreePointLocator.h>
 
int main(int, char *[])
{
  // Create some random points
  vtkSmartPointer<vtkPointSource> pointSource = 
    vtkSmartPointer<vtkPointSource>::New();
  pointSource->SetNumberOfPoints(10);
  pointSource->Update();
 
  // Create the tree
  vtkSmartPointer<vtkOctreePointLocator> octree =
    vtkSmartPointer<vtkOctreePointLocator>::New();
  octree->SetDataSet(pointSource->GetOutput());
  octree->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();
 
  octree->FindPointsWithinRadius(1.0, 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;
}