# Light

VTKExamples/Cxx/Lighting/Light

### Code

Light.cxx

    #include <cstdlib>

    #include <vtkVersion.h>
    #include <vtkLightCollection.h>
    #include <vtkProperty.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkPlaneSource.h>
    #include <vtkSphereSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkLight.h>
    #include <vtkLightActor.h>
    #include <vtkSmartPointer.h>
    #include <vtkRenderWindowInteractor.h>

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

      double lightPosition[3] = {0, 0, 1};

      // Create a light
      double lightFocalPoint[3] = {0,0,0};

      vtkSmartPointer<vtkLight> light = vtkSmartPointer<vtkLight>::New();
      light->SetLightTypeToSceneLight();
      light->SetPosition(lightPosition[0], lightPosition[1], lightPosition[2]);
      light->SetPositional(true); // required for vtkLightActor below
      light->SetConeAngle(10);
      light->SetFocalPoint(lightFocalPoint[0], lightFocalPoint[1], lightFocalPoint[2]);
      light->SetDiffuseColor(1,0,0);
      light->SetAmbientColor(0,1,0);
      light->SetSpecularColor(0,0,1);

      vtkLightCollection* originalLights = renderer->GetLights();
      std::cout << "Originally there are " << originalLights->GetNumberOfItems() << " lights." << std::endl;

    //  renderer->AddLight(light); // can't do this here - must do this after the renderWindow->Render() below

      // Display where the light is
      vtkSmartPointer<vtkLightActor> lightActor = vtkSmartPointer<vtkLightActor>::New();
      lightActor->SetLight(light);
      renderer->AddViewProp(lightActor);

      // Display where the light is focused
      vtkSmartPointer<vtkSphereSource> lightFocalPointSphere = vtkSmartPointer<vtkSphereSource>::New();
      lightFocalPointSphere->SetCenter(lightFocalPoint);
      lightFocalPointSphere->SetRadius(.1);
      lightFocalPointSphere->Update();

      vtkSmartPointer<vtkPolyDataMapper> lightFocalPointMapper =
          vtkSmartPointer<vtkPolyDataMapper>::New();
      lightFocalPointMapper->SetInputConnection(lightFocalPointSphere->GetOutputPort());

      vtkSmartPointer<vtkActor> lightFocalPointActor = vtkSmartPointer<vtkActor>::New();
      lightFocalPointActor->SetMapper(lightFocalPointMapper);
      lightFocalPointActor->GetProperty()->SetColor(1.0, 1.0, 0.0); //(R,G,B)
      renderer->AddViewProp(lightFocalPointActor);

      // Create a plane for the light to shine on
      vtkSmartPointer<vtkPlaneSource> planeSource = vtkSmartPointer<vtkPlaneSource>::New();
      planeSource->SetResolution(100, 100);
      planeSource->Update();

      vtkSmartPointer<vtkPolyDataMapper> planeMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
      planeMapper->SetInput(planeSource->GetOutput());
    #else
      planeMapper->SetInputData(planeSource->GetOutput());
    #endif

      vtkSmartPointer<vtkActor> planeActor = vtkSmartPointer<vtkActor>::New();
      planeActor->SetMapper(planeMapper);
      renderer->AddActor(planeActor);

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

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

      renderWindow->Render();
      std::cout << "Now there are " << originalLights->GetNumberOfItems() << " lights." << std::endl;

      renderer->AddLight(light); // must do this after renderWindow->Render();
      std::cout << "Now there are " << originalLights->GetNumberOfItems() << " lights." << std::endl;

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(Light)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(Light MACOSX_BUNDLE Light.cxx )

    target_link_libraries(Light ${VTK_LIBRARIES})

### Download and Build Light

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

    cd Light/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:

    ./Light

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