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# ExtractFaces

VTKEx/Cxx/Utilities/ExtractFaces

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

ExtractFaces.cxx

    #include <vtkCellIterator.h>
    #include <vtkCellTypes.h>
    #include <vtkGenericCell.h>
    #include <vtkGenericDataSet.h>
    #include <vtkPointSet.h>
    #include <vtkSmartPointer.h>
    #include <vtkXMLGenericDataObjectReader.h>

    #include <map>

    int main(int argc, char* argv[])
    {
      std::map<std::string, int> cellMap;

      for (int arg = 1; arg < argc; ++arg)
      {
        auto reader =
          vtkSmartPointer<vtkXMLGenericDataObjectReader>::New();
        reader->SetFileName(argv[arg]);
        reader->Update();

        //    vtkPointSet *pointSet =
        //    vtkPointSet::SafeDownCast(reader->GetOutput());;
        vtkPointSet* pointSet = dynamic_cast<vtkPointSet*>(reader->GetOutput());
        ;
        auto it = pointSet->NewCellIterator();
        for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell())
        {
          auto cell = vtkSmartPointer<vtkGenericCell>::New();
          it->GetCell(cell);
          std::string cellName =
              vtkCellTypes::GetClassNameFromTypeId(cell->GetCellType());
          if (cellMap.count(cellName) == 0)
          {
            std::cout << "Type: " << cellName << " has " << cell->GetNumberOfFaces()
                      << " faces" << std::endl;
          }
          cellMap[cellName]++;
        }
        it->Delete();
      }
      for (auto itm = cellMap.begin(); itm != cellMap.end(); ++itm)
      {
        std::cout << itm->first << " occurs " << itm->second << " times"
                  << std::endl;
      }

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ExtractFaces)

    find_package(VTK COMPONENTS
      vtkvtkCommonCore
      vtkvtkCommonDataModel
      vtkvtkIOXML QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ExtractFaces: ${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(ExtractFaces MACOSX_BUNDLE ExtractFaces.cxx )
      target_link_libraries(ExtractFaces PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ExtractFaces MACOSX_BUNDLE ExtractFaces.cxx )
      target_link_libraries(ExtractFaces PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ExtractFaces
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ExtractFaces

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

    cd ExtractFaces/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:

    ./ExtractFaces

WINDOWS USERS

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