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ExtractPolyLinesFromPolyData

vtk-examples/Cxx/PolyData/ExtractPolyLinesFromPolyData

Description

This example uses vtkCutter to create contour lines. It processes these lines with vtkStripper to create continuous poly lines. After exiting the example with the "e" key, the lines are printed.

Other languages

See (Python)

Question

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Code

ExtractPolyLinesFromPolyData.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCellArray.h>
#include <vtkColor.h>
#include <vtkCutter.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPlane.h>
#include <vtkPoints.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkStripper.h>

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

int main(int, char*[])
{
  // Define colors for example
  vtkNew<vtkNamedColors> colors;
  vtkColor3d lineColor = colors->GetColor3d("peacock");
  vtkColor3d modelColor = colors->GetColor3d("silver");
  vtkColor3d backgroundColor = colors->GetColor3d("wheat");

  vtkNew<vtkSphereSource> modelSource;

  vtkNew<vtkPlane> plane;

  vtkNew<vtkCutter> cutter;
  cutter->SetInputConnection(modelSource->GetOutputPort());
  cutter->SetCutFunction(plane);
  cutter->GenerateValues(10, -0.5, 0.5);

  vtkNew<vtkPolyDataMapper> modelMapper;
  modelMapper->SetInputConnection(modelSource->GetOutputPort());

  vtkNew<vtkActor> model;
  model->SetMapper(modelMapper);
  model->GetProperty()->SetDiffuseColor(modelColor.GetData());
  model->GetProperty()->SetInterpolationToFlat();

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

  vtkNew<vtkPolyDataMapper> linesMapper;
  linesMapper->SetInputConnection(stripper->GetOutputPort());

  vtkNew<vtkActor> lines;
  lines->SetMapper(linesMapper);
  lines->GetProperty()->SetDiffuseColor(lineColor.GetData());
  lines->GetProperty()->SetLineWidth(3.0);

  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;

  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);
  renderWindow->SetWindowName("ExtractPolyLinesFromPolyData");

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

  // Add the actors to the renderer
  renderer->AddActor(model);
  renderer->AddActor(lines);
  renderer->SetBackground(backgroundColor.GetData());
  renderer->GetActiveCamera()->Azimuth(-45);
  renderer->GetActiveCamera()->Elevation(-22.5);
  renderer->ResetCamera();

  // 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;
  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;

#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 3.3 FATAL_ERROR)

project(ExtractPolyLinesFromPolyData)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersSources
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping ExtractPolyLinesFromPolyData: ${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(ExtractPolyLinesFromPolyData MACOSX_BUNDLE ExtractPolyLinesFromPolyData.cxx )
  target_link_libraries(ExtractPolyLinesFromPolyData PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ExtractPolyLinesFromPolyData MACOSX_BUNDLE ExtractPolyLinesFromPolyData.cxx )
  target_link_libraries(ExtractPolyLinesFromPolyData PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ExtractPolyLinesFromPolyData
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build ExtractPolyLinesFromPolyData

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

cd ExtractPolyLinesFromPolyData/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:

./ExtractPolyLinesFromPolyData

WINDOWS USERS

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