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# CapClip

VTKEx/Cxx/Meshes/CapClip

### Description

This example shows how to generate a "cap" on a clipped vtkPolyData. After clipping with vtkClipPolyData, it uses a clever ''trick'' to convert polylines into polygons. If a polydata file is provided, it will cap it. Otherwise it caps a clipped sphere.

Warning

The clipping is done with a scalar field provided by vtkPlane and results may depend on the resolution of the input vtkPolyData.

Style

This example collects all of the color definition in the beginning of the example. This makes it easier to make changes to the colors without having to search the code.

Other languages

See (Python), (CSharp)

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

CapClip.cxx

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkClipPolyData.h>
    #include <vtkDataSetMapper.h>
    #include <vtkFeatureEdges.h>
    #include <vtkNamedColors.h>
    #include <vtkPlane.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSmartPointer.h>
    #include <vtkStripper.h>
    #include <vtkXMLPolyDataReader.h>

    // Readers
    #include <vtkBYUReader.h>
    #include <vtkOBJReader.h>
    #include <vtkPLYReader.h>
    #include <vtkPolyDataReader.h>
    #include <vtkSTLReader.h>
    #include <vtkXMLPolyDataReader.h>

    #include <vtkSphereSource.h>

    namespace {
    vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName);
    }

    //
    // Demonstrate the use of clipping and capping on polyhedral data
    //

    int main(int argc, char* argv[])
    {
      // Define colors
      auto colors = vtkSmartPointer<vtkNamedColors>::New();
      auto backgroundColor = colors->GetColor3d("steel_blue");
      auto boundaryColor = colors->GetColor3d("banana");
      auto clipColor = colors->GetColor3d("tomato");
      // PolyData to process
      auto polyData = ReadPolyData(argc > 1 ? argv[1] : "");

      auto plane = vtkSmartPointer<vtkPlane>::New();
      plane->SetOrigin(polyData->GetCenter());
      plane->SetNormal(1.0, -1.0, -1.0);

      auto clipper = vtkSmartPointer<vtkClipPolyData>::New();
      clipper->SetInputData(polyData);
      clipper->SetClipFunction(plane);
      clipper->SetValue(0);
      clipper->Update();

      polyData = clipper->GetOutput();

      auto clipMapper = vtkSmartPointer<vtkDataSetMapper>::New();
      clipMapper->SetInputData(polyData);

      auto clipActor = vtkSmartPointer<vtkActor>::New();
      clipActor->SetMapper(clipMapper);
      clipActor->GetProperty()->SetDiffuseColor(clipColor.GetData());
      clipActor->GetProperty()->SetInterpolationToFlat();
      clipActor->GetProperty()->EdgeVisibilityOn();

      // Now extract feature edges
      auto boundaryEdges = vtkSmartPointer<vtkFeatureEdges>::New();
      boundaryEdges->SetInputData(polyData);
      boundaryEdges->BoundaryEdgesOn();
      boundaryEdges->FeatureEdgesOff();
      boundaryEdges->NonManifoldEdgesOff();
      boundaryEdges->ManifoldEdgesOff();

      auto boundaryStrips = vtkSmartPointer<vtkStripper>::New();
      boundaryStrips->SetInputConnection(boundaryEdges->GetOutputPort());
      boundaryStrips->Update();

      // Change the polylines into polygons
      auto boundaryPoly = vtkSmartPointer<vtkPolyData>::New();
      boundaryPoly->SetPoints(boundaryStrips->GetOutput()->GetPoints());
      boundaryPoly->SetPolys(boundaryStrips->GetOutput()->GetLines());

      auto boundaryMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
      boundaryMapper->SetInputData(boundaryPoly);

      auto boundaryActor = vtkSmartPointer<vtkActor>::New();
      boundaryActor->SetMapper(boundaryMapper);
      boundaryActor->GetProperty()->SetDiffuseColor(boundaryColor.GetData());

      // Create graphics stuff
      //
      auto renderer = vtkSmartPointer<vtkRenderer>::New();
      renderer->SetBackground(backgroundColor.GetData());
      renderer->UseHiddenLineRemovalOn();

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

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

      // Add the actors to the renderer, set the background and size
      //
      renderer->AddActor(clipActor);
      renderer->AddActor(boundaryActor);

      // Generate an interesting view
      //
      renderer->ResetCamera();
      renderer->GetActiveCamera()->Azimuth(30);
      renderer->GetActiveCamera()->Elevation(30);
      renderer->GetActiveCamera()->Dolly(1.2);
      renderer->ResetCameraClippingRange();

      renderWindow->Render();
      renderWindow->SetWindowName("CapClip");
      renderWindow->Render();

      interactor->Start();

      return EXIT_SUCCESS;
    }
    namespace {
    vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName)
    {
      vtkSmartPointer<vtkPolyData> polyData;
      std::string extension = "";
      if (fileName.find_last_of(".") != std::string::npos)
      {
        extension = fileName.substr(fileName.find_last_of("."));
      }
      // Make the extension lowercase
      std::transform(extension.begin(), extension.end(), extension.begin(),
                     ::tolower);
      if (extension == ".ply")
      {
        auto reader = vtkSmartPointer<vtkPLYReader>::New();
        reader->SetFileName(fileName.c_str());
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtp")
      {
        auto reader = vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName(fileName.c_str());
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".obj")
      {
        auto reader = vtkSmartPointer<vtkOBJReader>::New();
        reader->SetFileName(fileName.c_str());
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".stl")
      {
        auto reader = vtkSmartPointer<vtkSTLReader>::New();
        reader->SetFileName(fileName.c_str());
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtk")
      {
        auto reader = vtkSmartPointer<vtkPolyDataReader>::New();
        reader->SetFileName(fileName.c_str());
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".g")
      {
        auto reader = vtkSmartPointer<vtkBYUReader>::New();
        reader->SetGeometryFileName(fileName.c_str());
        reader->Update();
        polyData = reader->GetOutput();
      }
      else
      {
        // Return a polydata sphere if the extension is unknown.
        auto source = vtkSmartPointer<vtkSphereSource>::New();
        source->SetThetaResolution(20);
        source->SetPhiResolution(11);
        source->Update();
        polyData = source->GetOutput();
      }
      return polyData;
    }
    } // namespace

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(CapClip)

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

### Download and Build CapClip

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

    cd CapClip/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:

    ./CapClip

WINDOWS USERS

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