# TextOrigin

VTKExamples/Cxx/Annotation/TextOrigin

### Description

This example demonstrates the use of vtkVectorText and vtkFollower. vtkVectorText is used to create 3D annotation. vtkFollower is used to position the 3D text and to ensure that the text always faces the renderer's active camera (i.e., the text is always readable).

Other Languages

See (Python), (Java)

### Code

TextOrigin.cxx

    // This example demonstrates the use of vtkVectorText and vtkFollower.
    // vtkVectorText is used to create 3D annotation.  vtkFollower is used to
    // position the 3D text and to ensure that the text always faces the
    // renderer's active camera (i.e., the text is always readable).

    #include <vtkSmartPointer.h>
    #include <vtkAxes.h>
    #include <vtkFollower.h>
    #include <vtkVectorText.h>

    #include <vtkNamedColors.h>
    #include <vtkCamera.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkInteractorStyleTrackballCamera.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>

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

    // Create the axes and the associated mapper and actor.
      vtkSmartPointer<vtkAxes> axes =
        vtkSmartPointer<vtkAxes>::New();
      axes->SetOrigin(0, 0, 0);
      vtkSmartPointer<vtkPolyDataMapper> axesMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      axesMapper->SetInputConnection(axes->GetOutputPort());
      vtkSmartPointer<vtkActor> axesActor =
        vtkSmartPointer<vtkActor>::New();
      axesActor->SetMapper(axesMapper);

    // Create the 3D text and the associated mapper and follower (a type of
    // actor).  Position the text so it is displayed over the origin of the
    // axes.
      vtkSmartPointer<vtkVectorText> atext =
        vtkSmartPointer<vtkVectorText>::New();
      atext->SetText("Origin");
      vtkSmartPointer<vtkPolyDataMapper> textMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      textMapper->SetInputConnection(atext->GetOutputPort());
      vtkSmartPointer<vtkFollower> textActor =
        vtkSmartPointer<vtkFollower>::New();
      textActor->SetMapper(textMapper);
      textActor->SetScale(0.2, 0.2, 0.2);
      textActor->AddPosition(0, -0.1, 0);

    // Create the Renderer, RenderWindow, and RenderWindowInteractor.
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderWindow->SetSize(640, 480);

      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      vtkSmartPointer<vtkInteractorStyleTrackballCamera> style =
        vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();
      interactor->SetInteractorStyle( style );

    // Add the actors to the renderer.
      renderer->AddActor(axesActor);
      renderer->AddActor(textActor);

      renderer->SetBackground(colors->GetColor3d("Silver").GetData());

    // Zoom in closer.
      renderer->ResetCamera();
      renderer->GetActiveCamera()->Zoom(1.6);

      renderer->SetBackground(colors->GetColor3d("Silver").GetData());

    // Reset the clipping range of the camera; set the camera of the
    // follower; render.
      renderer->ResetCameraClippingRange();
      textActor->SetCamera(renderer->GetActiveCamera());

      interactor->Initialize();
      renderWindow->Render();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(TextOrigin)

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

### Download and Build TextOrigin

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

    cd TextOrigin/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:

    ./TextOrigin

WINDOWS USERS

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