# 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 <vtkVersion.h>
    #include <vtkSmartPointer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkActor.h>
    #include <vtkProperty.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkStripper.h>
    #include <vtkCutter.h>
    #include <vtkSplineFilter.h>
    #include <vtkSpline.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>

    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();
    #if VTK_MAJOR_VERSION <= 5
      cutter->SetInput(polyData);
    #else
      cutter->SetInputData(polyData);
    #endif
      cutter->SetCutFunction(plane);
      cutter->GenerateValues(1, 0.0, 0.0);

      vtkSmartPointer<vtkPolyDataMapper> modelMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
      modelMapper->SetInput(polyData);
    #else
      modelMapper->SetInputData(polyData);
    #endif

      vtkSmartPointer<vtkActor> model =
        vtkSmartPointer<vtkActor>::New();
      model->SetMapper(modelMapper);

      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);

      vtkSmartPointer<vtkRenderer> ren =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();

      renWin->AddRenderer(ren);

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

      // Add the actors to the renderer
      ren->AddActor(lines);
      ren->SetBackground(0.1, 0.2, 0.4);

      // 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 2.8)

    PROJECT(FitSplineToCutterOutput)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(FitSplineToCutterOutput MACOSX_BUNDLE FitSplineToCutterOutput.cxx)

    target_link_libraries(FitSplineToCutterOutput ${VTK_LIBRARIES})

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