VTK/Examples/Cxx/DataStructures/vtkKdTree BuildLocatorFromPoints ClosestKPoints

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkPointSource.h>
#include <vtkIdList.h>
#include <vtkKdTree.h>
 
int main(int, char *[])
{
  // Create some points
  double origin[3] = {0.0, 0.0, 0.0};
  double x[3] = {1.0, 0.0, 0.0};
  double y[3] = {0.0, 1.0, 0.0};
  double z[3] = {0.0, 0.0, 1.0};
 
  vtkSmartPointer<vtkPoints> points = 
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(origin);
  points->InsertNextPoint(x);
  points->InsertNextPoint(y);
  points->InsertNextPoint(z);
 
  // Create the tree
  vtkSmartPointer<vtkKdTree> pointTree = 
    vtkSmartPointer<vtkKdTree>::New();
  pointTree->BuildLocatorFromPoints(points);
 
  // Find the 2 closest points to (0.5,0,0)
  vtkIdType k = 2;
  double testPoint[3] = {0.5, 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];
    points->GetPoint(point_ind, p);
    std::cout << "Closest point " 
              << i << ": Point " << point_ind << ": (" 
              << p[0] << ", " << p[1] << ", " << p[2] << ")" << std::endl;
    }
 
  return EXIT_SUCCESS;
}