# MarchingCubes

VTKExamples/Cxx/Modelling/MarchingCubes

### Description

Creates a surface from a volume using Marching Cubes.

Note

vtkVoxelModeller by default produces a VTK_BIT scalar image. Marching Cubes does not support this type. The scalar output is set to float for this example.

To generate a surface from a DICOM series, provide a folder containing the series and specify an isovalue for the surface.

This Midas Repository contains a number of DICOM datasets.

### Code

MarchingCubes.cxx

    #include <vtkVersion.h>
    #include <vtkSmartPointer.h>
    #include <vtkMarchingCubes.h>
    #include <vtkVoxelModeller.h>
    #include <vtkSphereSource.h>
    #include <vtkImageData.h>
    #include <vtkDICOMImageReader.h>

    #include <vtkActor.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>

    int main(int argc, char *argv[])
    {
      vtkSmartPointer<vtkImageData> volume =
        vtkSmartPointer<vtkImageData>::New();
      double isoValue;
      if (argc < 3)
      {
        vtkSmartPointer<vtkSphereSource> sphereSource =
          vtkSmartPointer<vtkSphereSource>::New();
        sphereSource->SetPhiResolution(20);
        sphereSource->SetThetaResolution(20);
        sphereSource->Update();

        double bounds[6];
        sphereSource->GetOutput()->GetBounds(bounds);
        for (unsigned int i = 0; i < 6; i += 2)
        {
          double range = bounds[i+1] - bounds[i];
          bounds[i]   = bounds[i] - .1 * range;
          bounds[i+1] = bounds[i+1] + .1 * range;
        }
        vtkSmartPointer<vtkVoxelModeller> voxelModeller =
          vtkSmartPointer<vtkVoxelModeller>::New();
        voxelModeller->SetSampleDimensions(50,50,50);
        voxelModeller->SetModelBounds(bounds);
        voxelModeller->SetScalarTypeToFloat();
        voxelModeller->SetMaximumDistance(.1);

        voxelModeller->SetInputConnection(sphereSource->GetOutputPort());
        voxelModeller->Update();
        isoValue = 0.5;
        volume->DeepCopy(voxelModeller->GetOutput());
      }
      else
      {
        vtkSmartPointer<vtkDICOMImageReader> reader =
          vtkSmartPointer<vtkDICOMImageReader>::New();
        reader->SetDirectoryName(argv[1]);
        reader->Update();
        volume->DeepCopy(reader->GetOutput());
        isoValue = atof(argv[2]);
      }

      vtkSmartPointer<vtkMarchingCubes> surface =
        vtkSmartPointer<vtkMarchingCubes>::New();

    #if VTK_MAJOR_VERSION <= 5
      surface->SetInput(volume);
    #else
      surface->SetInputData(volume);
    #endif
      surface->ComputeNormalsOn();
      surface->SetValue(0, isoValue);

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->SetBackground(.1, .2, .3);

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

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

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

      renderer->AddActor(actor);

      renderWindow->Render();
      interactor->Start();
      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(MarchingCubes)

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

    add_executable(MarchingCubes MACOSX_BUNDLE MarchingCubes.cxx )

    target_link_libraries(MarchingCubes ${VTK_LIBRARIES})

### Download and Build MarchingCubes

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

    cd MarchingCubes/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:

    ./MarchingCubes

WINDOWS USERS

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