# SelectVisiblePoints

VTKExamples/Cxx/PolyData/SelectVisiblePoints

### Description

This example demonstrates how to determine which objects are visible.

### Code

SelectVisiblePoints.cxx

    #include <vtkPolyData.h>
    #include <vtkPointSource.h>
    #include <vtkSphereSource.h>
    #include <vtkSmartPointer.h>
    #include <vtkSelectVisiblePoints.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkInteractorStyleTrackballCamera.h>
    #include <vtkObjectFactory.h>

    class MyInteractor : public vtkInteractorStyleTrackballCamera
    {
      public:

        static MyInteractor* New();
        vtkTypeMacro(MyInteractor, vtkInteractorStyleTrackballCamera);

        virtual void OnLeftButtonDown()
        {
          this->VisibleFilter->Update();
          std::cout << "There are currently: " << this->VisibleFilter->GetOutput()->GetNumberOfPoints()
                    << " visible." << std::endl;
          // Forward events
          vtkInteractorStyleTrackballCamera::OnLeftButtonDown();

        }

        void SetVisibleFilter(vtkSmartPointer<vtkSelectVisiblePoints> vis) {this->VisibleFilter = vis;}
      private:
        vtkSmartPointer<vtkSelectVisiblePoints> VisibleFilter;
    };

    vtkStandardNewMacro(MyInteractor);

    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetCenter(5.0, 0, 0);
      sphereSource->Update();

      vtkSmartPointer<vtkPointSource> pointSource =
          vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetRadius(2.0);
      pointSource->SetNumberOfPoints(200);
      pointSource->Update();

      // Create an actor and mapper
      vtkSmartPointer<vtkPolyDataMapper> sphereMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      sphereMapper->SetInputConnection(sphereSource->GetOutputPort());

      vtkSmartPointer<vtkActor> sphereActor =
        vtkSmartPointer<vtkActor>::New();
      sphereActor->SetMapper(sphereMapper);

      vtkSmartPointer<vtkPolyDataMapper> pointsMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      pointsMapper->SetInputConnection(pointSource->GetOutputPort());

      vtkSmartPointer<vtkActor> pointsActor =
        vtkSmartPointer<vtkActor>::New();
      pointsActor->SetMapper(pointsMapper);

      // Create a renderer, render window, and interactor
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Add the actors to the scene
      renderer->AddActor(sphereActor);
      renderer->AddActor(pointsActor);

      vtkSmartPointer<vtkSelectVisiblePoints> selectVisiblePoints =
        vtkSmartPointer<vtkSelectVisiblePoints>::New();
      selectVisiblePoints->SetInputConnection(pointSource->GetOutputPort());
      selectVisiblePoints->SetRenderer(renderer);
      selectVisiblePoints->Update();

      vtkSmartPointer<MyInteractor> style =
        vtkSmartPointer<MyInteractor>::New();
      renderWindowInteractor->SetInteractorStyle( style );
      style->SetVisibleFilter(selectVisiblePoints);

      // Render and interact
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(SelectVisiblePoints)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping SelectVisiblePoints: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(SelectVisiblePoints MACOSX_BUNDLE SelectVisiblePoints.cxx )
      target_link_libraries(SelectVisiblePoints PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(SelectVisiblePoints MACOSX_BUNDLE SelectVisiblePoints.cxx )
      target_link_libraries(SelectVisiblePoints PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS SelectVisiblePoints
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build SelectVisiblePoints

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

    cd SelectVisiblePoints/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:

    ./SelectVisiblePoints

WINDOWS USERS

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