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FitSplineToCutterOutput

vtk-examples/Cxx/PolyData/FitSplineToCutterOutput

Description

This examples cuts a vtkPolydata and fits a vtkKochanekSpline to the resulting polylines. The cut lines are passed through vtkStripper to make them into connected polylines. Then, 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.

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

FitSplineToCutterOutput.cxx

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

#ifdef VTK_CELL_ARRAY_V2
#include <vtkCellArrayIterator.h>
#endif // VTK_CELL_ARRAY_V2

#include <iostream>
#include <string>

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

  double length = polyData->GetLength();

  vtkNew<vtkPlane> plane;
  plane->SetNormal(0, 1, 1);
  plane->SetOrigin(polyData->GetCenter());

  vtkNew<vtkCutter> cutter;
  cutter->SetInputData(polyData);
  cutter->SetCutFunction(plane);
  cutter->GenerateValues(1, 0.0, 0.0);

  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkPolyDataMapper> modelMapper;
  modelMapper->SetInputData(polyData);

  vtkNew<vtkActor> model;
  model->SetMapper(modelMapper);
  model->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());
  model->GetProperty()->SetInterpolationToFlat();

  vtkNew<vtkStripper> stripper;
  stripper->SetInputConnection(cutter->GetOutputPort());

  vtkNew<vtkKochanekSpline> spline;
  spline->SetDefaultTension(.5);

  vtkNew<vtkSplineFilter> sf;
  sf->SetInputConnection(stripper->GetOutputPort());
  sf->SetSubdivideToSpecified();
  sf->SetNumberOfSubdivisions(50);
  sf->SetSpline(spline);
  sf->GetSpline()->ClosedOn();

  vtkNew<vtkTubeFilter> tubes;
  tubes->SetInputConnection(sf->GetOutputPort());
  tubes->SetNumberOfSides(8);
  tubes->SetRadius(length / 100.0);

  vtkNew<vtkPolyDataMapper> linesMapper;
  linesMapper->SetInputConnection(tubes->GetOutputPort());
  linesMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> lines;
  lines->SetMapper(linesMapper);
  lines->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());

  vtkNew<vtkRenderer> renderer;
  renderer->UseHiddenLineRemovalOn();

  vtkNew<vtkRenderWindow> renderWindow;
  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

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

  renderer->ResetCamera();
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());
  renderer->GetActiveCamera()->Azimuth(300);
  renderer->GetActiveCamera()->Elevation(30);
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);
  renderWindow->SetWindowName("FitSplineToCutterOutput");

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

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

  std::cout << "-----------Lines without using vtkStripper" << std::endl;
  if (numberOfLines == 1)
  {
    std::cout << "There is " << numberOfLines << " line in the polydata"
              << std::endl;
  }
  else
  {
    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;
  if (numberOfLines == 1)
  {
    std::cout << "There is " << numberOfLines << " line in the polydata"
              << std::endl;
  }
  else
  {

    std::cout << "There are " << numberOfLines << " lines in the polydata"
              << std::endl;
  }

#ifdef VTK_CELL_ARRAY_V2

  // Newer versions of vtkCellArray prefer local iterators:
  auto cellIter = vtk::TakeSmartPointer(cells->NewIterator());
  for (cellIter->GoToFirstCell(); !cellIter->IsDoneWithTraversal();
       cellIter->GoToNextCell())
  {
    std::cout << "Line " << cellIter->GetCurrentCellId() << ":\n";

    vtkIdList* cell = cellIter->GetCurrentCell();
    for (vtkIdType i = 0; i < cell->GetNumberOfIds(); ++i)
    {
      double point[3];
      points->GetPoint(cell->GetId(i), point);
      std::cout << "\t(" << point[0] << ", " << point[1] << ", " << point[2]
                << ")" << std::endl;
    }
  }

#else // VTK_CELL_ARRAY_V2

  // Older implementations of vtkCellArray use internal iterator APIs (not
  // thread safe):
  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;
    }
  }

#endif // VTK_CELL_ARRAY_V2

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(FitSplineToCutterOutput)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "FitSplineToCutterOutput: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
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}
)

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.