Skip to content


# ClipUnstructuredGridWithPlane

VTKEx/Cxx/UnstructuredGrid/ClipUnstructuredGridWithPlane

### Description

The example uses vtkTableBasedClipDataSet to clip a vtkUnstructuredGrid. The resulting output and clipped output are presented in yellow and red respectively. To illustrate the clipped interfaces, the example uses a vtkTransform to rotate each output about their centers.

Note that unlike other clipping filters (except for vtkClipPolyData), vtkTableBasedClipDataSet retains the original cells if they are not clipped.

After exiting, the example reports the number of each cell type for each output:

    The inside dataset contains a
      vtkUnstructuredGrid that has 26116 cells
        Cell type vtkTetra occurs 3751 times.
        Cell type vtkHexahedron occurs 17361 times.
        Cell type vtkWedge occurs 628 times.
        Cell type vtkPyramid occurs 4376 times.
    The clipped dataset contains a
      vtkUnstructuredGrid that has 25655 cells
        Cell type vtkTetra occurs 3715 times.
        Cell type vtkHexahedron occurs 16984 times.
        Cell type vtkWedge occurs 616 times.
        Cell type vtkPyramid occurs 4340 times.

Compare these results with ClipUnstructuredGridWithPlane2 (C++), ClipUnstructuredGridWithPlane2 (Python). Also, the resulting vtkUnstructuredGrid's has 1/4 the number of cells.

usage

ClipUnstructuredGridWithPlane treemesh.vtk

thanks

Thanks to Bane Sullivan for sharing the treemesh.vtk unstructured grid dataset.

Other languages

See (Python)

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

ClipUnstructuredGridWithPlane.cxx

    #include <vtkSmartPointer.h>
    #include <vtkTableBasedClipDataSet.h>
    #include <vtkUnstructuredGridReader.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkPlane.h>
    #include <vtkTransform.h>

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkCellTypes.h>
    #include <vtkDataSetMapper.h>
    #include <vtkLookupTable.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>

    #include <vtkNamedColors.h>

    int main(int argc, char *argv[])
    {
      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0] << " filename.vtk" << std::endl;
        return EXIT_FAILURE;
      }
      // Create the reader for the data.
      std::string filename = argv[1];
      std::cout << "Loading " << filename.c_str() << std::endl;
      auto reader =
        vtkSmartPointer<vtkUnstructuredGridReader>::New();
      reader->SetFileName(filename.c_str());
      reader->Update();

      double bounds[6];
      reader->GetOutput()->GetBounds(bounds);
      double center[3];
      reader->GetOutput()->GetCenter(center);

      auto colors =
        vtkSmartPointer<vtkNamedColors>::New();
      auto renderer = vtkSmartPointer<vtkRenderer>::New();
      renderer->SetBackground(colors->GetColor3d("Wheat").GetData());
      renderer->UseHiddenLineRemovalOn();

      auto renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderWindow->SetSize(640, 480);

      auto interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      double xnorm[3] = {-1.0, -1.0, 1.0};

      auto clipPlane = vtkSmartPointer<vtkPlane>::New();
      clipPlane->SetOrigin(reader->GetOutput()->GetCenter());
      clipPlane->SetNormal(xnorm);

      auto clipper =
        vtkSmartPointer<vtkTableBasedClipDataSet>::New();
      clipper->SetClipFunction(clipPlane);
      clipper->SetInputData(reader->GetOutput());
      clipper->SetValue(0.0);
      clipper->GenerateClippedOutputOn();
      clipper->Update();

      auto insideMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      insideMapper->SetInputData(clipper->GetOutput());
      insideMapper->ScalarVisibilityOff();

      auto insideActor =
        vtkSmartPointer<vtkActor>::New();
      insideActor->SetMapper(insideMapper);
      insideActor->GetProperty()->SetDiffuseColor(colors->GetColor3d("banana").GetData());
      insideActor->GetProperty()->SetAmbient(.3);
      insideActor->GetProperty()->EdgeVisibilityOn();

      auto clippedMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      clippedMapper->SetInputData(clipper->GetClippedOutput());
      clippedMapper->ScalarVisibilityOff();

      auto clippedActor =
        vtkSmartPointer<vtkActor>::New();
      clippedActor->SetMapper(clippedMapper);
      clippedActor->GetProperty()->SetDiffuseColor(colors->GetColor3d("tomato").GetData());
      insideActor->GetProperty()->SetAmbient(.3);
      clippedActor->GetProperty()->EdgeVisibilityOn();

      // Create transforms to make a better visualization
      auto insideTransform = vtkSmartPointer<vtkTransform>::New();
      insideTransform->Translate(-(bounds[1] - bounds[0]) * .75, 0, 0);
      insideTransform->Translate(center[0], center[1], center[2]);
      insideTransform->RotateY(-120.0);
      insideTransform->Translate(-center[0], -center[1], -center[2]);
      insideActor->SetUserTransform(insideTransform);

      auto clippedTransform = vtkSmartPointer<vtkTransform>::New();
      clippedTransform->Translate((bounds[1] - bounds[0]) * .75, 0, 0);
      clippedTransform->Translate(center[0], center[1], center[2]);
      clippedTransform->RotateY(60.0);
      clippedTransform->Translate(-center[0], -center[1], -center[2]);
      clippedActor->SetUserTransform(clippedTransform);

      renderer->AddViewProp(clippedActor);
      renderer->AddViewProp(insideActor);

      renderer->ResetCamera();
      renderer->GetActiveCamera()->Dolly(1.4);
      renderer->ResetCameraClippingRange();
      renderWindow->Render();
      renderWindow->SetWindowName("ClipUnstructuredGridWithPlane");
      renderWindow->Render();

      interactor->Start();

      // Generate a report
      vtkIdType numberOfCells = clipper->GetOutput()->GetNumberOfCells();
      std::cout << "------------------------" << std::endl;
      std::cout << "The inside dataset contains a " << std::endl
                << clipper->GetOutput()->GetClassName()
                <<  " that has " << numberOfCells << " cells" << std::endl;
      typedef std::map<int,int> CellContainer;
      CellContainer cellMap;
      for (vtkIdType i = 0; i < numberOfCells; i++)
      {
        cellMap[clipper->GetOutput()->GetCellType(i)]++;
      }

      for (auto c : cellMap)
      {
        std::cout << "\tCell type "
                  << vtkCellTypes::GetClassNameFromTypeId(c.first)
                  << " occurs " << c.second << " times." << std::endl;
      }

      numberOfCells = clipper->GetClippedOutput()->GetNumberOfCells();
      std::cout << "------------------------" << std::endl;
      std::cout << "The clipped dataset contains a " << std::endl
                << clipper->GetClippedOutput()->GetClassName()
                <<  " that has " << numberOfCells << " cells" << std::endl;
      typedef std::map<int,int> OutsideCellContainer;
      CellContainer outsideCellMap;
      for (vtkIdType i = 0; i < numberOfCells; i++)
      {
        outsideCellMap[clipper->GetClippedOutput()->GetCellType(i)]++;
      }

      for (auto c : outsideCellMap)
      {
        std::cout << "\tCell type "
                  << vtkCellTypes::GetClassNameFromTypeId(c.first)
                  << " occurs " << c.second << " times." << std::endl;
      }
      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ClipUnstructuredGridWithPlane)

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

### Download and Build ClipUnstructuredGridWithPlane

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

    cd ClipUnstructuredGridWithPlane/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:

    ./ClipUnstructuredGridWithPlane

WINDOWS USERS

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