AddCell

#include <vtkSmartPointer.h>
#include <vtkTriangle.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>

int main(int , char *[])
{
  // Create a triangle
  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint ( 1.0, 0.0, 0.0 );
  points->InsertNextPoint ( 0.0, 0.0, 0.0 );
  points->InsertNextPoint ( 0.0, 1.0, 0.0 );

  vtkSmartPointer<vtkTriangle> triangle =
    vtkSmartPointer<vtkTriangle>::New();
  triangle->GetPointIds()->SetId ( 0, 0 );
  triangle->GetPointIds()->SetId ( 1, 1 );
  triangle->GetPointIds()->SetId ( 2, 2 );

  vtkSmartPointer<vtkCellArray> triangles =
    vtkSmartPointer<vtkCellArray>::New();
  triangles->InsertNextCell ( triangle );

  // Create a polydata object
  vtkSmartPointer<vtkPolyData> polyData =
    vtkSmartPointer<vtkPolyData>::New();

  // Add the geometry and topology to the polydata
  polyData->SetPoints ( points );
  polyData->SetPolys ( triangles );

  std::cout << "There are " << polyData->GetNumberOfCells() << " cells." << std::endl;

  polyData->GetPolys()->InsertNextCell(triangle);

  std::cout << "There are " << polyData->GetNumberOfCells() << " cells." << std::endl;

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(AddCell)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel QUIET)
if (NOT VTK_FOUND)
  message("Skipping AddCell: ${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(AddCell MACOSX_BUNDLE AddCell.cxx )
  target_link_libraries(AddCell PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(AddCell MACOSX_BUNDLE AddCell.cxx )
  target_link_libraries(AddCell PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS AddCell
    MODULES ${VTK_LIBRARIES}
    )
endif () 

cd AddCell/build 

cmake ..

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

make

./AddCell