IterateOverLines

#include <vtkCellArray.h>
#include <vtkLine.h>
#include <vtkNew.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>

int main(int, char*[])
{
  double origin[3] = {0.0, 0.0, 0.0};
  double p0[3] = {1.0, 0.0, 0.0};
  double p1[3] = {0.0, 1.0, 0.0};
  double p2[3] = {0.0, 1.0, 2.0};
  double p3[3] = {1.0, 2.0, 3.0};

  // Create a vtkPoints object and store the points in it
  vtkNew<vtkPoints> points;
  points->InsertNextPoint(origin);
  points->InsertNextPoint(p0);
  points->InsertNextPoint(p1);
  points->InsertNextPoint(p2);
  points->InsertNextPoint(p3);

  // Create a cell array to store the lines in and add the lines to it
  vtkNew<vtkCellArray> lines;

  // Create four lines
  for (unsigned int i = 0; i < 4; i++)
  {
    vtkNew<vtkLine> line;
    line->GetPointIds()->SetId(0, i);
    line->GetPointIds()->SetId(1, i + 1);
    lines->InsertNextCell(line);
  }

  // Create a polydata to store everything in
  vtkNew<vtkPolyData> linesPolyData;

  // Add the points to the dataset
  linesPolyData->SetPoints(points);

  // Add the lines to the dataset
  linesPolyData->SetLines(lines);

  std::cout << "There are " << linesPolyData->GetNumberOfLines() << " lines."
            << std::endl;

  linesPolyData->GetLines()->InitTraversal();
  vtkNew<vtkIdList> idList;
  while (linesPolyData->GetLines()->GetNextCell(idList))
  {
    std::cout << "Line has " << idList->GetNumberOfIds() << " points."
              << std::endl;

    for (vtkIdType pointId = 0; pointId < idList->GetNumberOfIds(); pointId++)
    {
      std::cout << idList->GetId(pointId) << " ";
    }
    std::cout << std::endl;
  }
  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(IterateOverLines)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "IterateOverLines: 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(IterateOverLines MACOSX_BUNDLE IterateOverLines.cxx )
  target_link_libraries(IterateOverLines PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS IterateOverLines
  MODULES ${VTK_LIBRARIES}
)

cd IterateOverLines/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./IterateOverLines