# ClosestNPoints

VTKExamples/Cxx/DataStructures/KdTreePointLocator/ClosestNPoints

### Code

ClosestNPoints.cxx

    #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;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ClosestNPoints)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(ClosestNPoints MACOSX_BUNDLE ClosestNPoints.cxx )

    target_link_libraries(ClosestNPoints ${VTK_LIBRARIES})

### Download and Build ClosestNPoints

Click here to download ClosestNPoints and its CMakeLists.txt file. Once the tarball ClosestNPoints.tar has been downloaded and extracted,

    cd ClosestNPoints/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./ClosestNPoints

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.