ExtractClusters

VTKEx/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.

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

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 
  vtkvtkCommonCore
  vtkvtkFiltersCore
  vtkvtkFiltersPoints
  vtkvtkFiltersSources
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 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.