# Shadows

VTKExamples/Cxx/Visualization/Shadows

### Code

Shadows.cxx

    // The scene consists of
    // * 4 actors: a rectangle, a box, a cone and a sphere. The box, the cone and
    // the sphere are above the rectangle.
    // * 2 spotlights: one in the direction of the box, another one in the
    // direction of the sphere. Both lights are above the box, the cone and
    // the sphere.
    #include <vtkActor.h>
    #include <vtkSmartPointer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderWindow.h>

    #include <vtkOpenGLRenderer.h>

    #include <vtkLightActor.h>
    #include <vtkFrameBufferObject.h>
    #include <vtkImageSinusoidSource.h>
    #include <vtkImageData.h>
    #include <vtkImageDataGeometryFilter.h>
    #include <vtkDataSetSurfaceFilter.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkLookupTable.h>
    #include <vtkCamera.h>
    #include <vtkCameraPass.h>
    #include <vtkLightsPass.h>
    #include <vtkSequencePass.h>
    #include <vtkOpaquePass.h>
    #include <vtkDepthPeelingPass.h>
    #include <vtkTranslucentPass.h>
    #include <vtkVolumetricPass.h>
    #include <vtkOverlayPass.h>
    #include <vtkRenderPassCollection.h>
    #include <vtkShadowMapBakerPass.h>
    #include <vtkShadowMapPass.h>
    #include <vtkConeSource.h>
    #include <vtkPlaneSource.h>
    #include <vtkCubeSource.h>
    #include <vtkSphereSource.h>
    #include <vtkInformation.h>
    #include <vtkProperty.h>
    #include <vtkLight.h>
    #include <vtkLightCollection.h>
    #include <assert.h>
    #include <vtkMath.h>
    #include <vtkFrustumSource.h>
    #include <vtkPlanes.h>
    #include <vtkActorCollection.h>
    #include <vtkPolyDataNormals.h>
    #include <vtkPointData.h>

    // For each spotlight, add a light frustum wireframe representation and a cone
    // wireframe representation, colored with the light color.
    void AddLightActors(vtkRenderer *r);

    int main(int, char*[])
    {
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(400,400);
      renderWindow->SetMultiSamples(0);

      renderWindow->SetAlphaBitPlanes(1);
      interactor->SetRenderWindow(renderWindow);

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

      bool supported = vtkFrameBufferObject::IsSupported(renderWindow); // adapted from line 182 of vtkShadowMapPass.cxx

      if(!supported)
      {
        std::cerr << "Shadow rendering is not supported by the current video"
                  << " driver!" << std::endl;
        return EXIT_FAILURE;
      }

      vtkSmartPointer<vtkCameraPass> cameraP =
        vtkSmartPointer<vtkCameraPass>::New();

      vtkSmartPointer<vtkOpaquePass> opaque =
        vtkSmartPointer<vtkOpaquePass>::New();

      vtkSmartPointer<vtkDepthPeelingPass> peeling =
        vtkSmartPointer<vtkDepthPeelingPass>::New();
      peeling->SetMaximumNumberOfPeels(200);
      peeling->SetOcclusionRatio(0.1);

      vtkSmartPointer<vtkTranslucentPass> translucent =
        vtkSmartPointer<vtkTranslucentPass>::New();
      peeling->SetTranslucentPass(translucent);

      vtkSmartPointer<vtkVolumetricPass> volume =
        vtkSmartPointer<vtkVolumetricPass>::New();
      vtkSmartPointer<vtkOverlayPass> overlay =
        vtkSmartPointer<vtkOverlayPass>::New();

      vtkSmartPointer<vtkLightsPass> lights =
        vtkSmartPointer<vtkLightsPass>::New();

      vtkSmartPointer<vtkSequencePass> opaqueSequence =
        vtkSmartPointer<vtkSequencePass>::New();

      vtkSmartPointer<vtkRenderPassCollection> passes2 =
        vtkSmartPointer<vtkRenderPassCollection>::New();
      passes2->AddItem(lights);
      passes2->AddItem(opaque);
      opaqueSequence->SetPasses(passes2);

      vtkSmartPointer<vtkCameraPass> opaqueCameraPass =
        vtkSmartPointer<vtkCameraPass>::New();
      opaqueCameraPass->SetDelegatePass(opaqueSequence);

      vtkSmartPointer<vtkShadowMapBakerPass> shadowsBaker =
        vtkSmartPointer<vtkShadowMapBakerPass>::New();
      shadowsBaker->SetOpaquePass(opaqueCameraPass);
      shadowsBaker->SetResolution(1024);
      // To cancel self-shadowing.
      shadowsBaker->SetPolygonOffsetFactor(3.1f);
      shadowsBaker->SetPolygonOffsetUnits(10.0f);

      vtkSmartPointer<vtkShadowMapPass> shadows =
        vtkSmartPointer<vtkShadowMapPass>::New();
      shadows->SetShadowMapBakerPass(shadowsBaker);
      shadows->SetOpaquePass(opaqueSequence);

      vtkSmartPointer<vtkSequencePass> seq =
        vtkSmartPointer<vtkSequencePass>::New();
      vtkSmartPointer<vtkRenderPassCollection> passes =
        vtkSmartPointer<vtkRenderPassCollection>::New();
      passes->AddItem(shadowsBaker);
      passes->AddItem(shadows);
      passes->AddItem(lights);
      passes->AddItem(peeling);
      passes->AddItem(volume);
      passes->AddItem(overlay);
      seq->SetPasses(passes);
      cameraP->SetDelegatePass(seq);

      renderer->SetPass(cameraP);

      vtkSmartPointer<vtkPlaneSource> rectangleSource =
        vtkSmartPointer<vtkPlaneSource>::New();
      rectangleSource->SetOrigin(-5.0,0.0,5.0);
      rectangleSource->SetPoint1(5.0,0.0,5.0);
      rectangleSource->SetPoint2(-5.0,0.0,-5.0);
      rectangleSource->SetResolution(100,100);

      vtkSmartPointer<vtkPolyDataMapper> rectangleMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      rectangleMapper->SetInputConnection(rectangleSource->GetOutputPort());

      rectangleMapper->SetScalarVisibility(0);

      vtkSmartPointer<vtkActor> rectangleActor =
        vtkSmartPointer<vtkActor>::New();
      vtkSmartPointer<vtkInformation> rectangleKeyProperties =
        vtkSmartPointer<vtkInformation>::New();
      rectangleKeyProperties->Set(vtkShadowMapBakerPass::OCCLUDER(),0); // dummy val.
      rectangleKeyProperties->Set(vtkShadowMapBakerPass::RECEIVER(),0); // dummy val.
      rectangleActor->SetPropertyKeys(rectangleKeyProperties);

      rectangleActor->SetMapper(rectangleMapper);
      rectangleActor->SetVisibility(1);
      rectangleActor->GetProperty()->SetColor(1.0,1.0,1.0);

      vtkSmartPointer<vtkCubeSource> boxSource =
        vtkSmartPointer<vtkCubeSource>::New();
      boxSource->SetXLength(2.0);
      vtkSmartPointer<vtkPolyDataNormals> boxNormals =
        vtkSmartPointer<vtkPolyDataNormals>::New();
      boxNormals->SetInputConnection(boxSource->GetOutputPort());
      boxNormals->SetComputePointNormals(0);
      boxNormals->SetComputeCellNormals(1);
      boxNormals->Update();
      boxNormals->GetOutput()->GetPointData()->SetNormals(0);

      vtkSmartPointer<vtkPolyDataMapper> boxMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      boxMapper->SetInputConnection(boxNormals->GetOutputPort());
      boxMapper->SetScalarVisibility(0);

      vtkSmartPointer<vtkActor> boxActor =
        vtkSmartPointer<vtkActor>::New();
      vtkSmartPointer<vtkInformation> boxKeyProperties =
        vtkSmartPointer<vtkInformation>::New();
      boxKeyProperties->Set(vtkShadowMapBakerPass::OCCLUDER(),0); // dummy val.
      boxKeyProperties->Set(vtkShadowMapBakerPass::RECEIVER(),0); // dummy val.
      boxActor->SetPropertyKeys(boxKeyProperties);

      boxActor->SetMapper(boxMapper);
      boxActor->SetVisibility(1);
      boxActor->SetPosition(-2.0,2.0,0.0);
      boxActor->GetProperty()->SetColor(1.0,0.0,0.0);

      vtkSmartPointer<vtkConeSource> coneSource =
        vtkSmartPointer<vtkConeSource>::New();
      coneSource->SetResolution(24);
      coneSource->SetDirection(1.0,1.0,1.0);
      vtkSmartPointer<vtkPolyDataMapper> coneMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      coneMapper->SetInputConnection(coneSource->GetOutputPort());
      coneMapper->SetScalarVisibility(0);

      vtkSmartPointer<vtkActor> coneActor =
        vtkSmartPointer<vtkActor>::New();
      vtkSmartPointer<vtkInformation> coneKeyProperties=
        vtkSmartPointer<vtkInformation>::New();
      coneKeyProperties->Set(vtkShadowMapBakerPass::OCCLUDER(),0); // dummy val.
      coneKeyProperties->Set(vtkShadowMapBakerPass::RECEIVER(),0); // dummy val.
      coneActor->SetPropertyKeys(coneKeyProperties);

      coneActor->SetMapper(coneMapper);
      coneActor->SetVisibility(1);
      coneActor->SetPosition(0.0,1.0,1.0);
      coneActor->GetProperty()->SetColor(0.0,0.0,1.0);
    //  coneActor->GetProperty()->SetLighting(false);

      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetThetaResolution(32);
      sphereSource->SetPhiResolution(32);
      vtkSmartPointer<vtkPolyDataMapper> sphereMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      sphereMapper->SetInputConnection(sphereSource->GetOutputPort());
      sphereMapper->SetScalarVisibility(0);

      vtkSmartPointer<vtkActor> sphereActor =
        vtkSmartPointer<vtkActor>::New();
      vtkSmartPointer<vtkInformation> sphereKeyProperties =
        vtkSmartPointer<vtkInformation>::New();
      sphereKeyProperties->Set(vtkShadowMapBakerPass::OCCLUDER(),0); // dummy val.
      sphereKeyProperties->Set(vtkShadowMapBakerPass::RECEIVER(),0); // dummy val.
      sphereActor->SetPropertyKeys(sphereKeyProperties);
      sphereActor->SetMapper(sphereMapper);

      sphereActor->SetVisibility(1);
      sphereActor->SetPosition(2.0,2.0,-1.0);
      sphereActor->GetProperty()->SetColor(1.0,1.0,0.0);

      renderer->AddViewProp(rectangleActor);
      renderer->AddViewProp(boxActor);
      renderer->AddViewProp(coneActor);
      renderer->AddViewProp(sphereActor);

      // Spotlights.

      // lighting the box.
      vtkSmartPointer<vtkLight> l1 =
        vtkSmartPointer<vtkLight>::New();
      l1->SetPosition(-4.0,4.0,-1.0);
      l1->SetFocalPoint(boxActor->GetPosition());
      l1->SetColor(1.0,1.0,1.0);
      l1->SetPositional(1);
      renderer->AddLight(l1);
      l1->SetSwitch(1);

      // lighting the sphere
      vtkSmartPointer<vtkLight> l2 =
        vtkSmartPointer<vtkLight>::New();
      l2->SetPosition(4.0,5.0,1.0);
      l2->SetFocalPoint(sphereActor->GetPosition());
      l2->SetColor(1.0,0.0,1.0);
    //  l2->SetColor(1.0,1.0,1.0);
      l2->SetPositional(1);
      renderer->AddLight(l2);
      l2->SetSwitch(1);

      AddLightActors(renderer);

      renderer->SetBackground(0.66,0.66,0.66);
      renderer->SetBackground2(157.0/255.0*0.66,186/255.0*0.66,192.0/255.0*0.66);
      renderer->SetGradientBackground(true);

      renderWindow->Render();
      if(peeling->GetLastRenderingUsedDepthPeeling())
      {
        std::cout << "depth peeling was used" << std::endl;
      }
      else
      {
        std::cout << "depth peeling was not used (alpha blending instead)" << std::endl;
      }

      renderer->ResetCamera();
      vtkSmartPointer<vtkCamera> camera = renderer->GetActiveCamera();
      camera->Azimuth(40.0);
      camera->Elevation(10.0);

      renderWindow->Render();

      interactor->Start();

      return EXIT_SUCCESS;
    }

    // For each spotlight, add a light frustum wireframe representation and a cone
    // wireframe representation, colored with the light color.
    void AddLightActors(vtkRenderer *r)
    {
      assert("pre: r_exists" && r!=0);

      vtkLightCollection *lights=r->GetLights();

      lights->InitTraversal();
      vtkLight *l=lights->GetNextItem();
      while(l!=0)
      {
        double angle=l->GetConeAngle();
        if(l->LightTypeIsSceneLight() && l->GetPositional()
           && angle<180.0) // spotlight
        {
          vtkSmartPointer<vtkLightActor> la=
            vtkSmartPointer<vtkLightActor>::New();
          la->SetLight(l);
          r->AddViewProp(la);
        }
        l=lights->GetNextItem();
      }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(Shadows)

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

### Download and Build Shadows

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

    cd Shadows/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:

    ./Shadows

WINDOWS USERS

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