# CellCenters

VTKExamples/Cxx/PolyData/CellCenters

### Code

CellCenters.cxx

    #include <vtkSmartPointer.h>
    #include <vtkImageData.h>
    #include <vtkProperty.h>
    #include <vtkCellCenters.h>
    #include <vtkDataSetMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    int main(int, char *[])
    {
      // Create an image data
      vtkSmartPointer<vtkImageData> imageData =
        vtkSmartPointer<vtkImageData>::New();

      // Specify the size of the image data
      imageData->SetDimensions(3,3,2);
      imageData->SetSpacing(1.0, 1.0, 1.0);
      imageData->SetOrigin(0.0, 0.0, 0.0);

      vtkSmartPointer<vtkCellCenters> cellCentersFilter =
        vtkSmartPointer<vtkCellCenters>::New();
      cellCentersFilter->SetInputData(imageData);
      cellCentersFilter->VertexCellsOn();
      cellCentersFilter->Update();

      // Access the cell centers
      for(vtkIdType i = 0; i < cellCentersFilter->GetOutput()->GetNumberOfPoints(); i++)
      {
        double p[3];
        cellCentersFilter->GetOutput()->GetPoint(i, p);
        cout << "Point " << i << " : " << p[0] << " , " << p[1] << " , " << p[2] << endl;
      }

      // Display the cell centers
      vtkSmartPointer<vtkDataSetMapper> centerMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      centerMapper->SetInputConnection(cellCentersFilter->GetOutputPort());
      vtkSmartPointer<vtkActor> centerActor =
        vtkSmartPointer<vtkActor>::New();
      centerActor->SetMapper(centerMapper);

      vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      mapper->SetInputData(imageData);

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

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();

      renderWindow->AddRenderer(renderer);

      renderer->AddActor(actor);
      renderer->AddActor(centerActor);

      renderer->ResetCamera();

      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(CellCenters)

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

### Download and Build CellCenters

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

    cd CellCenters/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:

    ./CellCenters

WINDOWS USERS

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