# CameraModifiedEvent

VTKExamples/Cxx/Utilities/CameraModifiedEvent

### Code

CameraModifiedEvent.cxx

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

    static void CameraModifiedCallback(vtkObject* caller,
                                       long unsigned int vtkNotUsed(eventId),
                                       void* vtkNotUsed(clientData),
                                       void* vtkNotUsed(callData) )
    {
      std::cout << caller->GetClassName() << " modified" << std::endl;

      vtkCamera* camera = static_cast<vtkCamera*>(caller);
      // print the interesting stuff
      std::cout << "\tPosition: "
                << camera->GetPosition()[0] << ", "
                << camera->GetPosition()[1] << ", "
                << camera->GetPosition()[2] << std::endl;
      std::cout << "\tFocal point: "
                << camera->GetFocalPoint()[0] << ", "
                << camera->GetFocalPoint()[1] << ", "
                << camera->GetFocalPoint()[2] << std::endl;
    }

    int main(int, char *[])
    {
      // Create a sphere
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->Update();

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

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

      // 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();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Add the actor to the scene
      renderer->AddActor(actor);
      renderer->SetBackground(.1, .3, .5);

      vtkSmartPointer<vtkCallbackCommand> modifiedCallback =
        vtkSmartPointer<vtkCallbackCommand>::New();
      modifiedCallback->SetCallback (CameraModifiedCallback);

      renderer->ResetCamera();
      renderer->GetActiveCamera()->AddObserver(vtkCommand::ModifiedEvent,modifiedCallback);

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(CameraModifiedEvent)

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

### Download and Build CameraModifiedEvent

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

    cd CameraModifiedEvent/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:

    ./CameraModifiedEvent

WINDOWS USERS

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