# Slider

VTKExamples/Cxx/Widgets/Slider

### Description

This example demonstrates how to use a 3D slider widget. Here, the slider controls the resolution of the sphere. The slider is positioned in world coordinates - so if you rotate/translate/scale the scene, the slider will change orientation/position/size. Contrast this with Slider2D that remains at a fixed location in the window.

If the callback is connected to InteractionEvent, the scene will update whenever the mouse is moved on the slider. This is not ideal if the re-rendering takes significant time as it will make the interaction very choppy. If you want to move the slider and have the scene update when the mouse button is released, connect the callback to EndInteractionEvent instead.

Note

This original source code for this example is here.

### Code

Slider.cxx

    #include <vtkSphereSource.h>
    #include <vtkSmartPointer.h>
    #include <vtkPolyData.h>
    #include <vtkSliderWidget.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkPolyData.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>
    #include <vtkCommand.h>
    #include <vtkWidgetEvent.h>
    #include <vtkCallbackCommand.h>
    #include <vtkWidgetEventTranslator.h>
    #include <vtkInteractorStyleTrackballCamera.h>
    #include <vtkSliderWidget.h>
    #include <vtkSliderRepresentation3D.h>
    #include <vtkProperty.h>

    // The callback does the work.
    // The callback keeps a pointer to the sphere whose resolution is
    // controlled. After constructing the callback, the program sets the
    // SphereSource of the callback to
    // the object to be controlled.
    class vtkSliderCallback : public vtkCommand
    {
    public:
      static vtkSliderCallback *New()
      {
        return new vtkSliderCallback;
      }
      virtual void Execute(vtkObject *caller, unsigned long, void*)
      {
        vtkSliderWidget *sliderWidget =
          reinterpret_cast<vtkSliderWidget*>(caller);
        this->SphereSource->SetPhiResolution(static_cast<vtkSliderRepresentation *>(sliderWidget->GetRepresentation())->GetValue()/2);
        this->SphereSource->SetThetaResolution(static_cast<vtkSliderRepresentation *>(sliderWidget->GetRepresentation())->GetValue());
      }
      vtkSliderCallback():SphereSource(0) {}
      vtkSphereSource *SphereSource;
    };

    int main (int, char *[])
    {
      // A sphere
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetCenter(0.0, 0.0, 0.0);
      sphereSource->SetRadius(4.0);
      sphereSource->SetPhiResolution(4);
      sphereSource->SetThetaResolution(8);

      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(sphereSource->GetOutputPort());

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

      // 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);

      // Render an image (lights and cameras are created automatically)
      renderWindow->Render();

      vtkSmartPointer<vtkSliderRepresentation3D> sliderRep =
        vtkSmartPointer<vtkSliderRepresentation3D>::New();
      sliderRep->SetMinimumValue(3.0);
      sliderRep->SetMaximumValue(50.0);
      sliderRep->SetValue(sphereSource->GetThetaResolution());
      sliderRep->SetTitleText("Sphere Resolution");
      sliderRep->GetPoint1Coordinate()->SetCoordinateSystemToWorld();
      sliderRep->GetPoint1Coordinate()->SetValue(-4,6,0);
      sliderRep->GetPoint2Coordinate()->SetCoordinateSystemToWorld();
      sliderRep->GetPoint2Coordinate()->SetValue(4,6,0);
      sliderRep->SetSliderLength(0.075);
      sliderRep->SetSliderWidth(0.05);
      sliderRep->SetEndCapLength(0.05);

      vtkSmartPointer<vtkSliderWidget> sliderWidget =
        vtkSmartPointer<vtkSliderWidget>::New();
      sliderWidget->SetInteractor(renderWindowInteractor);
      sliderWidget->SetRepresentation(sliderRep);
      sliderWidget->SetAnimationModeToAnimate();
      sliderWidget->EnabledOn();

      vtkSmartPointer<vtkSliderCallback> callback =
        vtkSmartPointer<vtkSliderCallback>::New();
      callback->SphereSource = sphereSource;

      sliderWidget->AddObserver(vtkCommand::InteractionEvent,callback);

      renderWindowInteractor->Initialize();
      renderWindow->Render();

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(Slider)

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

### Download and Build Slider

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

    cd Slider/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:

    ./Slider

WINDOWS USERS

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