# ExtractSurface

VTKExamples/Cxx/Points/ExtractSurface

### Description

This example loosely follows the most excellent paper by Curless and Levoy: "A Volumetric Method for Building Complex Models from Range Images." First it estimates normals from the points, then creates a signed distance field, followed by surface extraction of the zero-level set of the distance field.

The image was created using the Armadillo dataset

Warning

The classes used in this example require vtk 7.1 or later.

### Code

ExtractSurface.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPLYReader.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkOBJReader.h>
    #include <vtkSTLReader.h>
    #include <vtkPointSource.h>

    #include <vtkPCANormalEstimation.h>
    #include <vtkSignedDistance.h>
    #include <vtkExtractSurface.h>
    #include <vtkPointData.h>

    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkCamera.h>

    #include <vtksys/SystemTools.hxx>

    static vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);

    int main (int argc, char *argv[])
    {
      vtkSmartPointer<vtkPolyData> polyData = ReadPolyData(argc > 1 ? argv[1] : "");;

      double bounds[6];
      polyData->GetBounds(bounds);
      double range[3];
      for (int i = 0; i < 3; ++i)
      {
        range[i] = bounds[2*i + 1] - bounds[2*i];
      }

      int sampleSize = polyData->GetNumberOfPoints() * .00005;
      if (sampleSize < 10)
      {
        sampleSize = 10;
      }
      std::cout << "Sample size is: " << sampleSize << std::endl;
      // Do we need to estimate normals?
      vtkSmartPointer<vtkSignedDistance> distance =
        vtkSmartPointer<vtkSignedDistance>::New();
      if (polyData->GetPointData()->GetNormals())
      {
        std::cout << "Using normals from input file" << std::endl;
        distance->SetInputData (polyData);
      }
      else
      {
        std::cout << "Estimating normals using PCANormalEstimation" << std::endl;
        vtkSmartPointer<vtkPCANormalEstimation> normals =
          vtkSmartPointer<vtkPCANormalEstimation>::New();
        normals->SetInputData (polyData);
        normals->SetSampleSize(sampleSize);
        normals->SetNormalOrientationToGraphTraversal();
        normals->FlipNormalsOn();
        distance->SetInputConnection (normals->GetOutputPort());
      }
      std::cout << "Range: "
                << range[0] << ", "
                << range[1] << ", "
                << range[2] << std::endl;
      int dimension = 256;
      double radius = range[0] * .02;
      radius = range[0] / static_cast<double>(dimension) * 3; // ~3 voxels
      std::cout << "Radius: " << radius << std::endl;

      distance->SetRadius(radius);
      distance->SetDimensions(dimension, dimension, dimension);
      distance->SetBounds(
        bounds[0] - range[0] * .1,
        bounds[1] + range[0] * .1,
        bounds[2] - range[1] * .1,
        bounds[3] + range[1] * .1,
        bounds[4] - range[2] * .1,
        bounds[5] + range[2] * .1);

      vtkSmartPointer<vtkExtractSurface> surface =
        vtkSmartPointer<vtkExtractSurface>::New();
      surface->SetInputConnection (distance->GetOutputPort());
      surface->SetRadius(radius * .99);
      surface->Update();

      vtkSmartPointer<vtkPolyDataMapper> surfaceMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      surfaceMapper->SetInputConnection(surface->GetOutputPort());

      vtkSmartPointer<vtkActor> surfaceActor =
        vtkSmartPointer<vtkActor>::New();
      surfaceActor->SetMapper(surfaceMapper);
      surfaceActor->GetProperty()->SetColor(1.0000,0.3882,0.2784);

      // Create graphics stuff
      //
      vtkSmartPointer<vtkRenderer> ren1 =
        vtkSmartPointer<vtkRenderer>::New();
      ren1->SetBackground(.3, .4, .6);

      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren1);
      renWin->SetSize(512,512);

      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      // Add the actors to the renderer, set the background and size
      //
      ren1->AddActor(surfaceActor);

      // Generate an interesting view
      //
      ren1->ResetCamera();
      ren1->GetActiveCamera()->Azimuth(120);
      ren1->GetActiveCamera()->Elevation(30);
      ren1->GetActiveCamera()->Dolly(1.0);
      ren1->ResetCameraClippingRange();

      iren->Initialize();
      iren->Start();

      return EXIT_SUCCESS;
    }

    static vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
    {
      vtkSmartPointer<vtkPolyData> polyData;
      std::string extension = vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
      if (extension == ".ply")
      {
        vtkSmartPointer<vtkPLYReader> reader =
          vtkSmartPointer<vtkPLYReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtp")
      {
        vtkSmartPointer<vtkXMLPolyDataReader> reader =
          vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".obj")
      {
        vtkSmartPointer<vtkOBJReader> reader =
          vtkSmartPointer<vtkOBJReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".stl")
      {
        vtkSmartPointer<vtkSTLReader> reader =
          vtkSmartPointer<vtkSTLReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else
      {
        vtkSmartPointer<vtkPointSource> points =
          vtkSmartPointer<vtkPointSource>::New();
        points->SetNumberOfPoints(100000);
        points->SetRadius(10.0);
        points->SetCenter(vtkMath::Random(-100, 100),
                          vtkMath::Random(-100, 100),
                          vtkMath::Random(-100, 100));
        points->SetDistributionToShell();
        points->Update();
        polyData = points->GetOutput();
      }
      return polyData;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ExtractSurface)

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

    add_executable(ExtractSurface MACOSX_BUNDLE ExtractSurface.cxx)

    target_link_libraries(ExtractSurface ${VTK_LIBRARIES})

### Download and Build ExtractSurface

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

    cd ExtractSurface/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:

    ./ExtractSurface

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.