ExtractPolyLinesFromPolyData

VTKExamples/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.

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code

ExtractPolyLinesFromPolyData.cxx

#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 <vtkPlane.h>
#include <vtkSphereSource.h>
#include <vtkPoints.h>
#include <vtkCellArray.h>

#include <vtkNamedColors.h>
#include <vtkColor.h>

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

  auto modelSource =
    vtkSmartPointer<vtkSphereSource>::New();

  auto plane =
    vtkSmartPointer<vtkPlane>::New();

  auto cutter =
    vtkSmartPointer<vtkCutter>::New();
  cutter->SetInputConnection(modelSource->GetOutputPort());
  cutter->SetCutFunction(plane);
  cutter->GenerateValues(10, -.5, .5);

  auto modelMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  modelMapper->SetInputConnection(modelSource->GetOutputPort());

  auto model =
    vtkSmartPointer<vtkActor>::New();
  model->SetMapper(modelMapper);
  model->GetProperty()->SetDiffuseColor(modelColor.GetData());
  model->GetProperty()->SetInterpolationToFlat();

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

  auto linesMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  linesMapper->SetInputConnection(stripper->GetOutputPort());

  auto lines =
    vtkSmartPointer<vtkActor>::New();
  lines->SetMapper(linesMapper);
  lines->GetProperty()->SetDiffuseColor(lineColor.GetData());
  lines->GetProperty()->SetLineWidth(3.0);

  auto renderer =
    vtkSmartPointer<vtkRenderer>::New();
  auto renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();

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

  auto interactor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  interactor->SetRenderWindow(renderWindow);

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

  // 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;

  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(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.