# SelectionSource

VTKExamples/Cxx/Filtering/SelectionSource

### Code

SelectionSource.cxx

    #include <vtkPointSource.h>
    #include <vtkExtractSelection.h>
    #include <vtkPolyData.h>
    #include <vtkSelectionNode.h> // for POINT and INDICES enum values
    #include <vtkSelectionSource.h>
    #include <vtkSmartPointer.h>

    int main(int, char *[])
    {
      // Note - this generates 50 points and a single poly-vertex cell.
      vtkSmartPointer<vtkPointSource> pointSource =
          vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetNumberOfPoints(50);
      pointSource->Update();

      std::cout << "There are " << pointSource->GetOutput()->GetNumberOfPoints() << " input points." << std::endl;

      vtkSmartPointer<vtkSelectionSource> selectionSource =
          vtkSmartPointer<vtkSelectionSource>::New();
      selectionSource->SetFieldType(vtkSelectionNode::POINT);
      selectionSource->SetContentType(vtkSelectionNode::INDICES);

      // Without this line, all points are passed through because the 11 points
      // we will select below are some of the points of the poly-vertex created
      // by the PointSource, so the cell (by default) gets passed through since
      // it contains some selected points, so therefore all of the points
      // (the 50 belonging to the poly-vertex) also get passed through, which
      // is not what we are trying to demonstrate.
      selectionSource->SetContainingCells(false);

      for (vtkIdType i = 10; i <= 20; i++)
      {
        selectionSource->AddID(0, i);
      }

      selectionSource->Update();

      vtkSmartPointer<vtkExtractSelection> extractSelection =
          vtkSmartPointer<vtkExtractSelection>::New();
      extractSelection->SetInputConnection(0, pointSource->GetOutputPort());
      extractSelection->SetInputConnection(1, selectionSource->GetOutputPort());
      extractSelection->Update();

      vtkDataSet* ds = vtkDataSet::SafeDownCast (extractSelection->GetOutput());

      std::cout << "There are " << ds->GetNumberOfPoints() << " output points." << std::endl;

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(SelectionSource)

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

### Download and Build SelectionSource

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

    cd SelectionSource/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:

    ./SelectionSource

WINDOWS USERS

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