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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 <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 3.12 FATAL_ERROR)

project(ExtractPolyLinesFromPolyData)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ExtractPolyLinesFromPolyData: 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(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}
)

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.