# PolyDataConnectivityFilter SpecifiedRegion

VTKExamples/Cxx/PolyData/PolyDataConnectivityFilter_SpecifiedRegion

### Description

This example creates two spheres and combines them together into one polydata. The vtkPolyDataConnectivityFilter is used to find the two spheres as they are separate regions (disconnected). If region 0 is selected, the small sphere is extracted. If region 1 is selected, the large sphere is extracted.

The original vtkPolyData is red, on top. The extracted region is yellow, on the bottom.

Note

Contrast this with PolyDataConnectivityFilter_LargestRegion.

Note

Contributed by: Jinyoung Hwang

Other Languages

See (CSharp)

### Code

PolyDataConnectivityFilter_SpecifiedRegion.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPolyDataConnectivityFilter.h>

    #include <vtkSphereSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkProperty.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkAppendPolyData.h>

    #include <vtkNamedColors.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkSphereSource> sphereSource1 =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource1->SetRadius(5);

      vtkSmartPointer<vtkSphereSource> sphereSource2 =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource2->SetRadius(10);
      sphereSource2->SetCenter(25,0,0);

      vtkSmartPointer<vtkAppendPolyData> appendFilter =
        vtkSmartPointer<vtkAppendPolyData>::New();
      appendFilter->AddInputConnection(sphereSource1->GetOutputPort());
      appendFilter->AddInputConnection(sphereSource2->GetOutputPort());

      vtkSmartPointer<vtkPolyDataConnectivityFilter> connectivityFilter =
        vtkSmartPointer<vtkPolyDataConnectivityFilter>::New();
      connectivityFilter->SetInputConnection(appendFilter->GetOutputPort());
      connectivityFilter->SetExtractionModeToSpecifiedRegions();
      connectivityFilter->AddSpecifiedRegion(0); //select the region to extract here
      connectivityFilter->Update();

      // Create a mapper and actor for original data
      vtkSmartPointer<vtkPolyDataMapper> originalMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      originalMapper->SetInputConnection(appendFilter->GetOutputPort());

      vtkSmartPointer<vtkActor> originalActor =
        vtkSmartPointer<vtkActor>::New();
      originalActor->SetMapper(originalMapper);
      originalActor->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());

      // create a mapper and actor for extracted data
      vtkSmartPointer<vtkPolyDataMapper> extractedMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      extractedMapper->SetInputConnection(connectivityFilter->GetOutputPort());

      vtkSmartPointer<vtkActor> extractedActor =
        vtkSmartPointer<vtkActor>::New();
      extractedActor->SetMapper(extractedMapper);
      extractedActor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
      extractedActor->SetPosition(0,-20,0);

      // create a renderer
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->AddActor(originalActor);
      renderer->AddActor(extractedActor);
      renderer->GradientBackgroundOn();
      renderer->SetBackground (colors->GetColor3d("Gold").GetData());
      renderer->SetBackground2 (colors->GetColor3d("Silver").GetData());

      // create a render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);

      // create an interactor
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);
      renderWindow->Render();
      interactor->Initialize();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(PolyDataConnectivityFilter_SpecifiedRegion)

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

### Download and Build PolyDataConnectivityFilter_SpecifiedRegion

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

    cd PolyDataConnectivityFilter_SpecifiedRegion/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:

    ./PolyDataConnectivityFilter_SpecifiedRegion

WINDOWS USERS

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