# ScalarBarActor

VTKExamples/Cxx/Visualization/ScalarBarActor

### Description

This example demonstrates how to make a color bar to that reflects the range of values associated with a data set.

### Code

ScalarBarActor.cxx

    #include <vtkActor.h>
    #include <vtkFloatArray.h>
    #include <vtkLookupTable.h>
    #include <vtkPointData.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkScalarBarActor.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>

    int main (int, char *[])
    {
      // Create a sphere for some geometry
      vtkSmartPointer<vtkSphereSource> sphere =
        vtkSmartPointer<vtkSphereSource>::New();
      sphere->SetCenter(0,0,0);
      sphere->SetRadius(1);
      sphere->Update();

      // Create scalar data to associate with the vertices of the sphere
      int numPts = sphere->GetOutput()->GetPoints()->GetNumberOfPoints();
      vtkSmartPointer<vtkFloatArray> scalars =
        vtkSmartPointer<vtkFloatArray>::New();
      scalars->SetNumberOfValues( numPts );
      for( int i = 0; i < numPts; ++i )
      {
        scalars->SetValue(i,static_cast<float>(i)/numPts);
      }
      vtkSmartPointer<vtkPolyData> poly =
        vtkSmartPointer<vtkPolyData>::New();
      poly->DeepCopy(sphere->GetOutput());
      poly->GetPointData()->SetScalars(scalars);

      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputData(poly);
      mapper->ScalarVisibilityOn();
      mapper->SetScalarModeToUsePointData();
      mapper->SetColorModeToMapScalars();

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

      vtkSmartPointer<vtkScalarBarActor> scalarBar =
        vtkSmartPointer<vtkScalarBarActor>::New();
      scalarBar->SetLookupTable(mapper->GetLookupTable());
      scalarBar->SetTitle("Title");
      scalarBar->SetNumberOfLabels(4);

      // Create a lookup table to share between the mapper and the scalarbar
      vtkSmartPointer<vtkLookupTable> hueLut =
        vtkSmartPointer<vtkLookupTable>::New();
      hueLut->SetTableRange (0, 1);
      hueLut->SetHueRange (0, 1);
      hueLut->SetSaturationRange (1, 1);
      hueLut->SetValueRange (1, 1);
      hueLut->Build();

      mapper->SetLookupTable( hueLut );
      scalarBar->SetLookupTable( hueLut );

      // Create a renderer and render window
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();

      renderer->GradientBackgroundOn();
      renderer->SetBackground(1,1,1);
      renderer->SetBackground2(0,0,0);

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);

      // Create an interactor
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Add the actors to the scene
      renderer->AddActor(actor);
      renderer->AddActor2D(scalarBar);

      // Render the scene (lights and cameras are created automatically)
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ScalarBarActor)

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

### Download and Build ScalarBarActor

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

    cd ScalarBarActor/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:

    ./ScalarBarActor

WINDOWS USERS

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