src/polygons.cpp (48bbb1b) - dxfngc · BlinkenArea

polygons.cpp

/* drawing (DXF) to G-code (NGC) converter
 * Copyright 2013 Stefan Schuermans <stefan@schuermans.info>
 * Copyleft: CC-BY-SA http://creativecommons.org/licenses/by-sa/3.0/
 */

#include <boost/shared_ptr.hpp>
#include <iostream>
#include <vector>

#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Polygon_2.h>
#include <CGAL/Polygon_with_holes_2.h>
#include <CGAL/create_offset_polygons_2.h>
#include <CGAL/Boolean_set_operations_2.h>

#include "layer.h"
#include "path.h"
#include "point.h"
#include "polygons.h"

/**
 * @brief clear all polygons
 */
void Polygons::clear()
{
  mPolys.clear();
}

/**
 * @brief add polygons from layer
 * @param[in] layer layer to obtain the polygons from
 * @param[in] eqDist maximum distance of two points to be considered equal
 * @return if the layer could be converted to polygons and imported
 */
bool Polygons::addLayer(const Layer &layer, double eqDist)
{
  // convert all paths to simple polygons
  CgPolyVec simples;
  Layer::Paths::const_iterator path;
  for (path = layer.mPaths.begin(); path != layer.mPaths.end(); ++path) {
    // skip empty paths
    if (path->mPoints.empty())
      continue;
    // check that path is closed
    if (!path->mPoints.front().equals(path->mPoints.back(), eqDist)) {
      std::cerr << "path not closed" << std::endl;
      return false;
    }
    // create simple polygon from path
    //   - do not add last point to polygon, as it is the same as the first one
    CgPoly simple;
    Path::Points::const_iterator pt;
    for (pt = path->mPoints.begin(); pt + 1 != path->mPoints.end(); ++pt)
      simple.push_back(CgPoint(pt->mX, pt->mY));
    // check that polygon is simple
    if (!simple.is_simple()) {
      std::cerr << "path is not simple (maybe self-itersecting?)" << std::endl;
      return false;
    }
    // ensure orientation is clockwise (must be the same for all polygons)
    if (simple.is_clockwise_oriented())
      simple.reverse_orientation();
    // collect polygons
    simples.push_back(simple);
  } // for path

// check that no partly overlaps are present
  // deterine which polygon is contained in which one
  std::vector<ssize_t> contained_in; // idx: contained poly, val: containing poly
  ssize_t ia, ib;
  CgPolyVec::const_iterator a, b;
  for (a = simples.begin(); a != simples.end(); ++a)
    contained_in.push_back(-1); // not contained in any polygon
  for (a = simples.begin(), ia = 0; a != simples.end(); ++a, ++ia) {
    b = a;
    ib = ia;
    for (++b, ++ib; b != simples.end(); ++b, ++ib) {
      // A and B intersect each other
      if (CGAL::do_intersect(*a, *b)) {
        // compute differences A - B and B - A
        CgPolyHolesVec a_b, b_a;
        CGAL::difference(*a, *b, std::back_inserter(a_b));
        CGAL::difference(*b, *a, std::back_inserter(b_a));
        if (a_b.empty()) {
          // A and B are identical
          if (b_a.empty()) {
            std::cerr << "duplicate polygons found - meaning is undefined"
                      << std::endl;
            return false;
          }
          // B contains A (A is hole in B)
          else {
            if (contained_in.at(ia) >= 0) {
              std::cerr << "polygon contained in multiple polygons"
                           " - meaning is undefined" << std::endl;
              return false;
            }
            contained_in.at(ia) = ib;
          }
        } else {
          // A contains B (B is hole in A)
          if (b_a.empty()) {
            if (contained_in.at(ib) >= 0) {
              std::cerr << "polygon contained in multiple polygons"
                           " - meaning is undefined" << std::endl;
              return false;
            }
            contained_in.at(ib) = ia;
          }
          // A and B overlap partly
          else {
            std::cerr << "polygons overlap partly - meaning is undefined"
                      << std::endl;
            return false;
          }
        }
      }
    } // for b
  } // for a

// add found polygons to member variable
  for (ia = 0; (size_t)ia < contained_in.size(); ++ia) {
    // outer polygon
    if (contained_in.at(ia) < 0) {
      CgPolyHoles poly(simples.at(ia));
      // find and add holes
      for (ib = 0; (size_t)ib < contained_in.size(); ++ib)
        if (contained_in.at(ib) == ia)
          poly.add_hole(simples.at(ib));
      // add polygon to member variable
      mPolys.push_back(poly);
    }
  }

return true;
}

/**
 * @brief load polygons from layer
 * @param[in] layer layer to obtain the polygons from
 * @param[in] eqDist maximum distance of two points to be considered equal
 * @return if the layer could be converted to polygons and imported
 */
bool Polygons::loadLayer(const Layer &layer, double eqDist)
{
  clear();
  return addLayer(layer, eqDist);
}

dxfngc

implement converting paths of layer into CGAL polygons