# SpotLights

VTKExamples/Cxx/Lighting/SpotLights

### Description

This example places two vtkLight's with PositionalOn().

Cite

This example was inspired by Oliver Natt's question (and python script) on the VTK Users mailing list.

### Code

SpotLights.cxx

    #include <vtkSmartPointer.h>

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

    int main (int, char *[])
    {
      // create a rendering window and renderer
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(640, 480);
      renderWindow->AddRenderer(renderer);

      // create a renderwindowinteractor
      vtkSmartPointer<vtkRenderWindowInteractor>   iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renderWindow);

      // create a plane and add it to the renderer
      vtkSmartPointer<vtkPlaneSource>   source =
        vtkSmartPointer<vtkPlaneSource>::New();
      source->SetOrigin(-5.0, 0.0, 5.0);
      source->SetPoint1(5.0, 0.0, 5.0);
      source->SetPoint2(-5.0, 0.0, -5.0);
      source->SetResolution(100, 100);
      vtkSmartPointer<vtkPolyDataMapper>   mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(source->GetOutputPort());

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

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

      // set camera view
      renderer->ResetCamera();
      renderer->GetActiveCamera()->Azimuth(40.0);
      renderer->GetActiveCamera()->Elevation(30.0);

      // create a green light
      vtkSmartPointer<vtkLight> greenLight =
        vtkSmartPointer<vtkLight>::New();
      greenLight->PositionalOn();
      greenLight->SetPosition(-4.0, 4.0, -1.0);
      greenLight->SetColor(colors->GetColor3d("Lawn_green").GetData());
      greenLight->SetIntensity(0.5);

      // create a pink light
      vtkSmartPointer<vtkLight> pinkLight =
        vtkSmartPointer<vtkLight>::New();
      pinkLight->PositionalOn();
      pinkLight->SetPosition(4.0, 5.0, 1.0);
      pinkLight->SetColor(colors->GetColor3d("DeepPink").GetData());
      pinkLight->SetIntensity(0.6);

      // add lights to the renderer
      renderer->AddLight(pinkLight);
      renderer->AddLight(greenLight);

      // define a background for better visibility
      renderer->SetBackground(colors->GetColor3d("RoyalBlue").GetData());
      renderer->SetBackground2(colors->GetColor3d("SkyBlue").GetData());
      renderer->GradientBackgroundOn();

      // enable interactor
      iren->Initialize();
      renderWindow->Render();
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(SpotLights)

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

### Download and Build SpotLights

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

    cd SpotLights/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:

    ./SpotLights

WINDOWS USERS

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