text: #include <vtkActor.h>
  #include <vtkCallbackCommand.h>
  #include <vtkCommand.h>
  #include <vtkInteractorStyleTrackballCamera.h>
  #include <vtkKdTree.h>
  #include <vtkMath.h>
  #include <vtkNamedColors.h>
  #include <vtkNew.h>
  #include <vtkPolyData.h>
  #include <vtkPolyDataMapper.h>
  #include <vtkProperty.h>
  #include <vtkProperty2D.h>
  #include <vtkRenderWindow.h>
  #include <vtkRenderWindowInteractor.h>
  #include <vtkRenderer.h>
  #include <vtkSliderRepresentation2D.h>
  #include <vtkSliderWidget.h>
  #include <vtkSmartPointer.h>
  #include <vtkTextProperty.h>
  #include <vtkWidgetEvent.h>
  #include <vtkWidgetEventTranslator.h>
  
  #include <vtkSphereSource.h>
  #include <vtkBYUReader.h>
  #include <vtkOBJReader.h>
  #include <vtkPLYReader.h>
  #include <vtkPolyDataReader.h>
  #include <vtkPolyDataReader.h>
  #include <vtkSTLReader.h>
  #include <vtkXMLPolyDataReader.h>
  
  #include <vtksys/SystemTools.hxx>
  
  namespace
  {
  vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);
  }
  
  namespace {
  class vtkSliderCallback : public vtkCommand {
  public:
    static vtkSliderCallback *New() { return new vtkSliderCallback; }
    vtkSliderCallback() : KdTree(0), Level(0), PolyData(0), Renderer(0) {}
  
    virtual void Execute(vtkObject *caller, unsigned long, void *) {
      vtkSliderWidget *sliderWidget = reinterpret_cast<vtkSliderWidget *>(caller);
      this->Level = vtkMath::Round(static_cast<vtkSliderRepresentation *>(
                                       sliderWidget->GetRepresentation())
                                       ->GetValue());
      this->KdTree->GenerateRepresentation(this->Level, this->PolyData);
      this->Renderer->Render();
    }
  
    vtkKdTree *KdTree;
    int Level;
    vtkPolyData *PolyData;
    vtkRenderer *Renderer;
  };
  } // namespace
  
  int main(int argc, char *argv[]) {
    vtkSmartPointer<vtkPolyData> polyData = ReadPolyData(argc > 1 ? argv[1] : "");;
  
    vtkNew<vtkNamedColors> colors;
  
    vtkSmartPointer<vtkPolyDataMapper> pointsMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
    pointsMapper->SetInputData(polyData);
    pointsMapper->ScalarVisibilityOff();
  
    vtkSmartPointer<vtkActor> pointsActor = vtkSmartPointer<vtkActor>::New();
    pointsActor->SetMapper(pointsMapper);
    pointsActor->GetProperty()->SetInterpolationToFlat();
    pointsActor->GetProperty()->SetColor(colors->GetColor4d("Yellow").GetData());
  
    int maxLevel = 20;
    // Create the tree
    vtkSmartPointer<vtkKdTree> kdTree =
        vtkSmartPointer<vtkKdTree>::New();
    kdTree->SetDataSet(polyData);
    kdTree->SetMaxLevel(maxLevel);
    kdTree->BuildLocator();
  
    // Initialize the representation
    vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();
    kdTree->GenerateRepresentation(maxLevel / 2, polydata);
  
    vtkSmartPointer<vtkPolyDataMapper> octreeMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
    octreeMapper->SetInputData(polydata);
  
    vtkSmartPointer<vtkActor> octreeActor = vtkSmartPointer<vtkActor>::New();
    octreeActor->SetMapper(octreeMapper);
    octreeActor->GetProperty()->SetInterpolationToFlat();
    octreeActor->GetProperty()->SetOpacity(.6);
    octreeActor->GetProperty()->EdgeVisibilityOn();
    octreeActor->GetProperty()->SetColor(
        colors->GetColor4d("SpringGreen").GetData());
  
    // A renderer and render window
    vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
    vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
    renderWindow->AddRenderer(renderer);
  
    // An interactor
    vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
    renderWindowInteractor->SetRenderWindow(renderWindow);
  
    // Add the actors to the scene
    renderer->AddActor(pointsActor);
    renderer->AddActor(octreeActor);
    renderer->SetBackground(colors->GetColor3d("MidnightBlue").GetData());
    renderer->SetUseDepthPeeling(1);
  
    // Render an image (lights and cameras are created automatically)
    renderWindow->SetWindowName("VisualizeKDTree");
    renderWindow->SetSize(600, 600);
    renderWindow->Render();
  
    vtkSmartPointer<vtkSliderRepresentation2D> sliderRep =
        vtkSmartPointer<vtkSliderRepresentation2D>::New();
    sliderRep->SetMinimumValue(0);
    sliderRep->SetMaximumValue(kdTree->GetLevel());
    sliderRep->SetValue(kdTree->GetLevel() / 2);
    sliderRep->SetTitleText("Level");
    sliderRep->GetPoint1Coordinate()->SetCoordinateSystemToNormalizedDisplay();
    sliderRep->GetPoint1Coordinate()->SetValue(.2, .2);
    sliderRep->GetPoint2Coordinate()->SetCoordinateSystemToNormalizedDisplay();
    sliderRep->GetPoint2Coordinate()->SetValue(.8, .2);
    sliderRep->SetSliderLength(0.075);
    sliderRep->SetSliderWidth(0.05);
    sliderRep->SetEndCapLength(0.05);
    sliderRep->GetTitleProperty()->SetColor(
        colors->GetColor3d("Beige").GetData());
    sliderRep->GetCapProperty()->SetColor(
        colors->GetColor3d("MistyRose").GetData());
    sliderRep->GetSliderProperty()->SetColor(
        colors->GetColor3d("LightBlue").GetData());
    sliderRep->GetSelectedProperty()->SetColor(
        colors->GetColor3d("Violet").GetData());
  
    vtkSmartPointer<vtkSliderWidget> sliderWidget =
        vtkSmartPointer<vtkSliderWidget>::New();
    sliderWidget->SetInteractor(renderWindowInteractor);
    sliderWidget->SetRepresentation(sliderRep);
    sliderWidget->SetAnimationModeToAnimate();
    sliderWidget->EnabledOn();
  
    vtkSmartPointer<vtkSliderCallback> callback =
        vtkSmartPointer<vtkSliderCallback>::New();
    callback->KdTree = kdTree;
    callback->PolyData = polydata;
    callback->Renderer = renderer;
    callback->Execute(sliderWidget, 0, 0);
  
    sliderWidget->AddObserver(vtkCommand::InteractionEvent, callback);
  
    // Ensure the current level is set
    callback->Execute(sliderWidget, 0, 0);
    renderWindowInteractor->Initialize();
    renderWindow->Render();
  
    renderWindowInteractor->Start();
  
    return EXIT_SUCCESS;
  }
  
  namespace
  {
  vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
  {
    vtkSmartPointer<vtkPolyData> polyData;
    std::string extension = vtksys::SystemTools::GetFilenameLastExtension(std::string(fileName));
    if (extension == ".ply")
    {
      vtkSmartPointer<vtkPLYReader> reader =
        vtkSmartPointer<vtkPLYReader>::New();
      reader->SetFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else if (extension == ".vtp")
    {
      vtkSmartPointer<vtkXMLPolyDataReader> reader =
        vtkSmartPointer<vtkXMLPolyDataReader>::New();
      reader->SetFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else if (extension == ".vtp")
    {
      vtkSmartPointer<vtkPolyDataReader> reader =
        vtkSmartPointer<vtkPolyDataReader>::New();
      reader->SetFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else if (extension == ".obj")
    {
      vtkSmartPointer<vtkOBJReader> reader =
        vtkSmartPointer<vtkOBJReader>::New();
      reader->SetFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else if (extension == ".stl")
    {
      vtkSmartPointer<vtkSTLReader> reader =
        vtkSmartPointer<vtkSTLReader>::New();
      reader->SetFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else if (extension == ".vtk")
    {
      vtkSmartPointer<vtkPolyDataReader> reader =
        vtkSmartPointer<vtkPolyDataReader>::New();
      reader->SetFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else if (extension == ".g")
    {
      vtkSmartPointer<vtkBYUReader> reader =
        vtkSmartPointer<vtkBYUReader>::New();
      reader->SetGeometryFileName (fileName);
      reader->Update();
      polyData = reader->GetOutput();
    }
    else
    {
      vtkSmartPointer<vtkSphereSource> source =
        vtkSmartPointer<vtkSphereSource>::New();
      source->SetPhiResolution(11);
      source->SetThetaResolution(11);
      source->Update();
      polyData = source->GetOutput();
    }
    return polyData;
  }
  }
  