PolygonIntersection

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkPolygon.h>

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

  // Create the polygon
  vtkSmartPointer<vtkPolygon> polygon = vtkSmartPointer<vtkPolygon>::New();
  polygon->GetPoints()->DeepCopy(points);
  polygon->GetPointIds()->SetNumberOfIds(4); // 4 corners of the square
  polygon->GetPointIds()->SetId(0, 0);
  polygon->GetPointIds()->SetId(1, 1);
  polygon->GetPointIds()->SetId(2, 2);
  polygon->GetPointIds()->SetId(3, 3);

  // Inputs
  double p1[3] = {0.1, 0, -1.0};
  double p2[3] = {0.1, 0, 1.0};
  double tolerance = 0.001;
  // Outputs
  double t; // Parametric coordinate of intersection (0 (corresponding to p1) to 1 (corresponding to p2))
  double x[3]; // The coordinate of the intersection
  double pcoords[3];
  int subId;

  vtkIdType iD = polygon->IntersectWithLine(p1, p2, tolerance, t, x, pcoords, subId);

  std::cout << "intersected? " << iD << std::endl;
  std::cout << "intersection: " << x[0] << " " << x[1] << " " << x[2] << std::endl;

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(PolygonIntersection)

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

cd PolygonIntersection/build 

cmake ..

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

make

./PolygonIntersection