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# Follower

VTKEx/Cxx/Visualization/Follower

### Description

The text is a 3D actor and is placed in 3D space, but stays right side up and facing the camera, while the cube does not.

Other languages

See (Java)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

Follower.cxx

    #include <vtkActor.h>
    #include <vtkCubeSource.h>
    #include <vtkFollower.h>
    #include <vtkInteractorStyle.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>
    #include <vtkVectorText.h>

    int main(int, char *[])
    {
      // Create some text
      vtkSmartPointer<vtkVectorText> textSource =
        vtkSmartPointer<vtkVectorText>::New();
      textSource->SetText( "Hello" );

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

      // Create a subclass of vtkActor: a vtkFollower that remains facing the camera
      vtkSmartPointer<vtkFollower> follower =
        vtkSmartPointer<vtkFollower>::New();
      follower->SetMapper( mapper );
      follower->GetProperty()->SetColor( 1, 0, 0 ); // red

      // Create a transparent cube that does not move around to face the camera
      vtkSmartPointer<vtkCubeSource> cubeSource =
        vtkSmartPointer<vtkCubeSource>::New();
      vtkSmartPointer<vtkPolyDataMapper> cubeMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      cubeMapper->SetInputConnection( cubeSource->GetOutputPort() );
      vtkSmartPointer<vtkActor> cubeActor =
        vtkSmartPointer<vtkActor>::New();
      cubeActor->SetMapper( cubeMapper );
      cubeActor->GetProperty()->SetColor( 0, 0, 1 ); // blue
      cubeActor->GetProperty()->SetOpacity( 0.3 );

      // 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();
      dynamic_cast<vtkInteractorStyle*>(renderWindowInteractor->GetInteractorStyle())->AutoAdjustCameraClippingRangeOn();
      renderWindowInteractor->SetRenderWindow( renderWindow );

      // Add the actor to the scene
      renderer->AddActor( follower );
      renderer->AddActor( cubeActor );
      renderer->SetBackground( 1, 1, 1 ); // Background color white
      follower->SetCamera( renderer->GetActiveCamera() );

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(Follower)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping Follower: ${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(Follower MACOSX_BUNDLE Follower.cxx )
      target_link_libraries(Follower PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(Follower MACOSX_BUNDLE Follower.cxx )
      target_link_libraries(Follower PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS Follower
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build Follower

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

    cd Follower/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:

    ./Follower

WINDOWS USERS

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