# FitSplineToCutterOutput

VTKExamples/Cxx/PolyData/FitSplineToCutterOutput

### Description

This examples cuts a polydata and fits a spline to the resulting polylines. The cut lines are passed through vtkStripper to make them into connected polylines. The lines are passed through vtkTubeFilter to improve the visualization.

The examples takes an optional argument that specifies a vtk polydata file (.vtp). If run without an argument, it processes a sphere.

### Code

FitSplineToCutterOutput.cxx

    #include <vtkSmartPointer.h>
    #include <vtkCutter.h>
    #include <vtkSplineFilter.h>
    #include <vtkSpline.h>

    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkProperty.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkStripper.h>
    #include <vtkPlane.h>
    #include <vtkSphereSource.h>
    #include <vtkPoints.h>
    #include <vtkCellArray.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkPolyData.h>
    #include <vtkTubeFilter.h>
    #include <vtkKochanekSpline.h>

    #include <vtkNamedColors.h>

    int main (int argc, char *argv[])
    {
      vtkSmartPointer<vtkPolyData> polyData =
        vtkSmartPointer<vtkPolyData>::New();
      if (argc > 1)
      {
        vtkSmartPointer<vtkXMLPolyDataReader> reader =
          vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName ( argv[1] );
        reader->Update();
        polyData = reader->GetOutput();
      }
      else
      {
        vtkSmartPointer<vtkSphereSource> modelSource =
          vtkSmartPointer<vtkSphereSource>::New();
        modelSource->Update();
        polyData = modelSource->GetOutput();
      }

      vtkSmartPointer<vtkPlane> plane =
        vtkSmartPointer<vtkPlane>::New();
      plane->SetNormal(0, 0, 1);

      vtkSmartPointer<vtkCutter> cutter =
        vtkSmartPointer<vtkCutter>::New();
      cutter->SetInputData(polyData);
      cutter->SetCutFunction(plane);
      cutter->GenerateValues(1, 0.0, 0.0);

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkPolyDataMapper> modelMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      modelMapper->SetInputData(polyData);

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

      vtkSmartPointer<vtkStripper> stripper =
        vtkSmartPointer<vtkStripper>::New();
      stripper->SetInputConnection(cutter->GetOutputPort());

      vtkSmartPointer<vtkKochanekSpline> spline =
        vtkSmartPointer<vtkKochanekSpline>::New();
      spline->SetDefaultTension(.5);

      vtkSmartPointer<vtkSplineFilter> sf =
        vtkSmartPointer<vtkSplineFilter>::New();
      sf->SetInputConnection(stripper->GetOutputPort());
      sf->SetSubdivideToSpecified();
      sf->SetNumberOfSubdivisions(50);
      sf->SetSpline(spline);
      sf->GetSpline()->ClosedOn();

      vtkSmartPointer<vtkTubeFilter> tubes =
        vtkSmartPointer<vtkTubeFilter>::New();
      tubes->SetInputConnection( sf->GetOutputPort());
      tubes->SetNumberOfSides(8);
      tubes->SetRadius(.02);

      vtkSmartPointer<vtkPolyDataMapper> linesMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      linesMapper->SetInputConnection(tubes->GetOutputPort());
      linesMapper->ScalarVisibilityOff();

      vtkSmartPointer<vtkActor> lines =
        vtkSmartPointer<vtkActor>::New();
      lines->SetMapper(linesMapper);
      lines->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());

      vtkSmartPointer<vtkRenderer> ren =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      // Add the actors to the renderer
      ren->AddActor(model);
      ren->AddActor(lines);

      ren->ResetCamera();
      ren->SetBackground(colors->GetColor3d("SlateGray").GetData());
      ren->GetActiveCamera()->Azimuth(300);
      ren->GetActiveCamera()->Elevation(30);
      renWin->AddRenderer(ren);

      // This starts the event loop and as a side effect causes an initial
      // render.
      renWin->Render();
      iren->Start();

      // Extract the lines from the polydata
      vtkIdType numberOfLines = cutter->GetOutput()->GetNumberOfLines();

      std::cout << "-----------Lines without using vtkStripper" << std::endl;
      std::cout << "There are "
                << numberOfLines
                << " lines in the polydata" << std::endl;

      numberOfLines = stripper->GetOutput()->GetNumberOfLines();
      vtkPoints *points = stripper->GetOutput()->GetPoints();
      vtkCellArray *cells = stripper->GetOutput()->GetLines();

      std::cout << "-----------Lines using vtkStripper" << std::endl;
      std::cout << "There are "
                << numberOfLines
                << " lines in the polydata" << std::endl;

      vtkIdType *indices;
      vtkIdType numberOfPoints;
      unsigned int lineCount = 0;
      for (cells->InitTraversal();
           cells->GetNextCell(numberOfPoints, indices);
           lineCount++)
      {
        std::cout << "Line " << lineCount << ": " << std::endl;
        for (vtkIdType i = 0; i < numberOfPoints; i++)
        {
          double point[3];
          points->GetPoint(indices[i], point);
          std::cout << "\t("
                    << point[0] << ", "
                    << point[1] << ", "
                    << point[2] << ")" << std::endl;
        }
      }
      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(FitSplineToCutterOutput)

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

### Download and Build FitSplineToCutterOutput

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

    cd FitSplineToCutterOutput/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:

    ./FitSplineToCutterOutput

WINDOWS USERS

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