# DecimateHawaii

VTKExamples/Cxx/VisualizationAlgorithms/DecimateHawaii

### Code

DecimateHawaii.cxx

    #include <vtkDecimatePro.h>

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkNamedColors.h>
    #include <vtkPNGReader.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkPolyDataNormals.h>
    #include <vtkPolyDataReader.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>

    int main (int argc, char *argv[])
    {
      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0] << " honolulu.vtk" << std::endl;
        return EXIT_FAILURE;
      }

    // This example shows how to use decimation to reduce a polygonal mesh. We also
    // use mesh smoothing and generate surface normals to give a pleasing result.
    //

      vtkSmartPointer<vtkPolyDataReader> hawaii =
        vtkSmartPointer<vtkPolyDataReader>::New();
      hawaii->SetFileName(argv[1]);

    // We want to preserve topology (not let any cracks form). This may limit
    // the total reduction possible, which we have specified at 90%.
    //
      vtkSmartPointer<vtkDecimatePro> deci =
        vtkSmartPointer<vtkDecimatePro>::New();
      deci->SetInputConnection(hawaii->GetOutputPort());
      deci->SetTargetReduction(0.9);
      deci->PreserveTopologyOn();

      vtkSmartPointer<vtkPolyDataNormals> decimatedNormals =
        vtkSmartPointer<vtkPolyDataNormals>::New();
      decimatedNormals->SetInputConnection(deci->GetOutputPort());
      decimatedNormals->FlipNormalsOn();
      decimatedNormals->SetFeatureAngle(60);

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

      vtkSmartPointer<vtkPolyDataMapper> decimatedMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      decimatedMapper->SetInputConnection(decimatedNormals->GetOutputPort());

      vtkSmartPointer<vtkActor> decimatedActor =
        vtkSmartPointer<vtkActor>::New();
      decimatedActor->SetMapper(decimatedMapper);
      decimatedActor->GetProperty()->SetColor(colors->GetColor3d("Aqua").GetData());
      decimatedActor->GetProperty()->SetRepresentationToWireframe();

      vtkSmartPointer<vtkPolyDataMapper> originalMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      originalMapper->SetInputConnection(decimatedNormals->GetOutputPort());

      vtkSmartPointer<vtkActor> originalActor =
        vtkSmartPointer<vtkActor>::New();
      originalActor->SetMapper(originalMapper);
      originalActor->GetProperty()->SetColor(colors->GetColor3d("Aqua").GetData());

    // Create the RenderWindow, Renderer and both Actors
    //
      vtkSmartPointer<vtkRenderer> renderer1 =
        vtkSmartPointer<vtkRenderer>::New();
      renderer1->SetViewport( 0., 0., 0.5, 1. );

      vtkSmartPointer<vtkRenderer> renderer2 =
        vtkSmartPointer<vtkRenderer>::New();
      renderer2->SetViewport( 0.5, 0., 1., 1. );

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer1);
      renderWindow->AddRenderer(renderer2);

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

    // Add the actors to the renderer, set the background and size
    //
      renderer1->AddActor(originalActor);
      renderer2->AddActor(decimatedActor);
      renderer1->SetBackground(colors->GetColor3d("Wheat").GetData());
      renderer2->SetBackground(colors->GetColor3d("Papaya_Whip").GetData());
      renderWindow->SetSize(800, 400);

    // render the image
    //
      vtkSmartPointer<vtkCamera> cam1 =
        vtkSmartPointer<vtkCamera>::New();
      cam1->SetFocalPoint(0, 0, 0);
      cam1->SetPosition(0, 0, 1);
      cam1->SetViewUp(0, 1, 0);
      renderer1->SetActiveCamera(cam1);
      renderer2->SetActiveCamera(cam1);
      renderer1->ResetCamera();
      cam1->Azimuth(30);
      cam1->Elevation(30);
      cam1->Dolly(1.3);
      renderer1->ResetCameraClippingRange();
      renderWindow->Render();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(DecimateHawaii)

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

    add_executable(DecimateHawaii MACOSX_BUNDLE DecimateHawaii.cxx )

    target_link_libraries(DecimateHawaii ${VTK_LIBRARIES})

### Download and Build DecimateHawaii

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

    cd DecimateHawaii/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:

    ./DecimateHawaii

WINDOWS USERS

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