# RubberBand2DObserver

VTKExamples/Cxx/Interaction/RubberBand2DObserver

### Code

RubberBand2DObserver.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkInteractorStyleRubberBand2D.h>
    #include <vtkCallbackCommand.h>

    void SelectionChangedCallbackFunction( vtkObject* caller,
      long unsigned int eventId, void* clientData, void* callData );

    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();

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

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      // 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(actor);
      renderer->SetBackground(1,1,1); // Background color white
      renderWindow->Render();

      vtkSmartPointer<vtkCallbackCommand> selectionChangedCallback =
        vtkSmartPointer<vtkCallbackCommand>::New();
      selectionChangedCallback->SetCallback ( SelectionChangedCallbackFunction );

      vtkSmartPointer<vtkInteractorStyleRubberBand2D> style =
        vtkSmartPointer<vtkInteractorStyleRubberBand2D>::New();
      style->AddObserver ( vtkCommand::SelectionChangedEvent, selectionChangedCallback );
      renderWindowInteractor->SetInteractorStyle( style );

      // Begin mouse interaction
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

    void SelectionChangedCallbackFunction ( vtkObject* vtkNotUsed(caller),
      long unsigned int vtkNotUsed(eventId), void* vtkNotUsed(clientData), void* callData )
    {
      std::cout << "SelectionChanged callback" << std::endl;

      unsigned int* rect = reinterpret_cast<unsigned int*> ( callData );
      unsigned int pos1X = rect[0];
      unsigned int pos1Y = rect[1];
      unsigned int pos2X = rect[2];
      unsigned int pos2Y = rect[3];

      std::cout << "Start x: " << pos1X << " Start y: " << pos1Y
                << " End x: " << pos2X << " End y: " << pos2Y << std::endl;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(RubberBand2DObserver)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping RubberBand2DObserver: ${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(RubberBand2DObserver MACOSX_BUNDLE RubberBand2DObserver.cxx )
      target_link_libraries(RubberBand2DObserver PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(RubberBand2DObserver MACOSX_BUNDLE RubberBand2DObserver.cxx )
      target_link_libraries(RubberBand2DObserver PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS RubberBand2DObserver
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build RubberBand2DObserver

Click here to download RubberBand2DObserver and its CMakeLists.txt file. Once the tarball RubberBand2DObserver.tar has been downloaded and extracted,

    cd RubberBand2DObserver/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:

    ./RubberBand2DObserver

WINDOWS USERS

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