# ExtractClusters

VTKExamples/Cxx/Points/ExtractClusters

### Description

This example extracts clusters of points. The points lie on spheres that are randomly placed. Each cluster has a different color. The number of extracted clusters may be less that the number of random spheres, if the points on one sphere are within the specified distance of points on another sphere.

Note

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

### Code

ExtractClusters.cxx

    #include <vtkSmartPointer.h>

    #include <vtkEuclideanClusterExtraction.h>
    #include <vtkPointSource.h>
    #include <vtkAppendPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkGlyph3D.h>

    #include <vtkLookupTable.h>

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

    int main (int, char *[])
    {
      vtkMath::RandomSeed(4355412); // for test result consistency
      double limits = 10;
      double radius = .5;

      vtkSmartPointer<vtkAppendPolyData> append =
        vtkSmartPointer<vtkAppendPolyData>::New();
      for (unsigned i = 0; i < 30; ++i)
      {
        vtkSmartPointer<vtkPointSource> points =
          vtkSmartPointer<vtkPointSource>::New();
        points->SetNumberOfPoints(800);
        points->SetRadius(2.5 * radius);
        points->SetCenter(vtkMath::Random(-limits, limits),
                          vtkMath::Random(-limits, limits),
                          vtkMath::Random(-limits, limits));
        points->SetDistributionToShell();

        append->AddInputConnection(points->GetOutputPort());
      }

      vtkSmartPointer<vtkEuclideanClusterExtraction> cluster =
        vtkSmartPointer<vtkEuclideanClusterExtraction>::New();
      cluster->SetInputConnection(append->GetOutputPort());
      cluster->SetExtractionModeToAllClusters();
      cluster->SetRadius(radius);
      cluster->ColorClustersOn();
      cluster->Update();

      std::cout << "Found " << cluster->GetNumberOfExtractedClusters()
                << " clusters within radius " << radius << std::endl;

      // Create a lookup table to map point data to colors
      vtkSmartPointer<vtkLookupTable> lut =
        vtkSmartPointer<vtkLookupTable>::New();
      int tableSize = cluster->GetNumberOfExtractedClusters();
      lut->SetNumberOfTableValues(tableSize);
      lut->Build();

      // Fill in the lookup table
      for (unsigned int i = 0; static_cast<int>(i) < tableSize; ++i)
      {
        lut->SetTableValue(i,
                           vtkMath::Random(.25, 1.0),
                           vtkMath::Random(.25, 1.0),
                           vtkMath::Random(.25, 1.0),
                           1.0);
      }

      vtkSmartPointer<vtkSphereSource> sphere =
        vtkSmartPointer<vtkSphereSource>::New();
      sphere->SetRadius(radius / 2.0);

      vtkSmartPointer<vtkGlyph3D> glyphs =
        vtkSmartPointer<vtkGlyph3D>::New();
      glyphs->SetInputConnection(cluster->GetOutputPort());
      glyphs->SetSourceConnection(sphere->GetOutputPort());
      glyphs->ScalingOff();
      glyphs->Update();

      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(glyphs->GetOutputPort());
      mapper->SetScalarRange(0, tableSize - 1);
      mapper->SetLookupTable(lut);

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

      // 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(640, 512);

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

      // Add the actors to the renderer
      //
      ren1->AddActor(actor);

      // Generate an interesting view
      //
      ren1->ResetCamera();
      ren1->GetActiveCamera()->Azimuth(120);
      ren1->GetActiveCamera()->Elevation(30);
      ren1->GetActiveCamera()->Dolly(1.5);
      ren1->ResetCameraClippingRange();

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ExtractClusters)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkFiltersCore
      vtkFiltersPoints
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ExtractClusters: ${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(ExtractClusters MACOSX_BUNDLE ExtractClusters.cxx )
      target_link_libraries(ExtractClusters PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ExtractClusters MACOSX_BUNDLE ExtractClusters.cxx )
      target_link_libraries(ExtractClusters PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ExtractClusters
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ExtractClusters

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

    cd ExtractClusters/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:

    ./ExtractClusters

WINDOWS USERS

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