cgal/Arrangement_on_surface_2/include/CGAL/Arr_overlay_2.h

// Copyright (c) 2005  Tel-Aviv University (Israel).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you may redistribute it under
// the terms of the Q Public License version 1.0.
// See the file LICENSE.QPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL$
// $Id$
// 
//
// Author(s)     : Baruch Zukerman <baruchzu@post.tau.ac.il>
//                 Efi Fogel <efif@post.tau.ac.il>

#ifndef CGAL_ARR_OVERLAY_2_H
#define CGAL_ARR_OVERLAY_2_H

/*! \file
 * Definition of the global Arr_overlay_2() function.
 */

#include <CGAL/Arrangement_on_surface_2.h>
#include <CGAL/Sweep_line_2.h>
#include <CGAL/Object.h>

#include <vector>
#include <boost/mpl/if.hpp>
#include <boost/type_traits.hpp>

CGAL_BEGIN_NAMESPACE

/*!
 * Compute the overlay of two input arrangements.
 * \param arr1 The first arrangement.
 * \param arr2 The second arrangement.
 * \param arr_res Output: The resulting arrangement.
 * \param ovl_tr An overlay-traits class. As arr1, arr2 and res are all
 *               templated with the same arrangement-traits class but with
 *               different DCELs (encapsulated in the various topology-traits
 *               classes), the overlay-traits class defines the various
 *               overlay operations of pairs of DCEL features from
 *               TopTraitsA and TopTraitsB to the resulting ResDcel.
 */
template <class GeomTraits,
          class TopTraitsA,
          class TopTraitsB,
          class TopTraitsRes,
          class OverlayTraits>
void overlay (const Arrangement_on_surface_2<GeomTraits, TopTraitsA>& arr1,
              const Arrangement_on_surface_2<GeomTraits, TopTraitsB>& arr2,
              Arrangement_on_surface_2<GeomTraits, TopTraitsRes>& arr_res,
              OverlayTraits& ovl_tr)
{
  typedef Arrangement_on_surface_2<GeomTraits, TopTraitsA>       ArrA;
  typedef Arrangement_on_surface_2<GeomTraits, TopTraitsB>       ArrB;
  typedef Arrangement_on_surface_2<GeomTraits, TopTraitsRes>     ArrRes;

  typedef typename TopTraitsRes::template
    Sweep_line_overlay_visitor<ArrA, ArrB, OverlayTraits>
                                                      Ovl_visitor;

  typedef typename Ovl_visitor::Traits_2              Ovl_traits_2;
  typedef typename Ovl_traits_2::X_monotone_curve_2   Ovl_x_monotone_curve_2;
  typedef typename Ovl_traits_2::Point_2              Ovl_point_2;
    
  // The result arrangement cannot be on of the input arrangements.
  CGAL_precondition(((void *)(&arr_res) != (void *)(&arr1)) && 
                    ((void *)(&arr_res) != (void *)(&arr2)));

  // Prepare a vector of extended x-monotone curves that represent all edges
  // in both input arrangements. Each curve is associated with a halfedge
  // directed from right to left.
  typename ArrA::Edge_const_iterator     eit1;
  typename ArrA::Halfedge_const_handle   he1, invalid_he1;
  typename ArrB::Edge_const_iterator     eit2;
  typename ArrB::Halfedge_const_handle   he2, invalid_he2;
  std::vector<Ovl_x_monotone_curve_2>    xcvs_vec (arr1.number_of_edges() +
                                                   arr2.number_of_edges());
  unsigned int                           i = 0;

  for (eit1 = arr1.edges_begin(); eit1 != arr1.edges_end(); ++eit1, i++)
  {
    he1 = eit1;
    if (he1->direction() != ARR_RIGHT_TO_LEFT)
      he1 = he1->twin();

    xcvs_vec[i] = Ovl_x_monotone_curve_2 (eit1->curve(),
                                          he1,
                                          invalid_he2);
  }

  for (eit2 = arr2.edges_begin(); eit2 != arr2.edges_end(); ++eit2, i++)
  {
    he2 = eit2;
    if (he2->direction() != ARR_RIGHT_TO_LEFT)
      he2 = he2->twin();

    xcvs_vec[i] = Ovl_x_monotone_curve_2 (eit2->curve(),
                                          invalid_he1,
                                          he2);
  }

  // Obtain a extended traits-class object and define the sweep-line visitor.
  GeomTraits               *geom_traits = arr_res.geometry_traits();

    /* We would like to avoid copy construction of the geometry traits class.
   * Copy construction is undesired, because it may results with data
   * duplication or even data loss.
   *
   * If the type Ovl_traits_2 is the same as the type
   * GeomTraits, use a reference to GeomTraits to avoid constructing a new one.
   * Otherwise, instantiate a local variable of the former and provide
   * the later as a single parameter to the constructor.
   * 
   * Use the form 'A a(*b);' and not ''A a = b;' to handle the case where A has
   * only an implicit constructor, (which takes *b as a parameter).
   */
  typename boost::mpl::if_<boost::is_same<GeomTraits, Ovl_traits_2>,
                           Ovl_traits_2&, Ovl_traits_2>::type
    ex_traits(*geom_traits);

  Ovl_visitor               visitor (&arr1, &arr2, &arr_res, &ovl_tr);
  Sweep_line_2<typename Ovl_visitor::Traits_2,
               Ovl_visitor,
               typename Ovl_visitor::Subcurve,
               typename Ovl_visitor::Event>
    sweep_line (&ex_traits, &visitor);

  // In case both arrangement do not contain isolated vertices, go on and
  // overlay them.
  const unsigned int  total_iso_verts = arr1.number_of_isolated_vertices() +
                                        arr2.number_of_isolated_vertices();

  if (total_iso_verts == 0)
  {
    // Clear the result arrangement and perform the sweep to construct it.
    arr_res.clear();

    sweep_line.sweep (xcvs_vec.begin(), xcvs_vec.end());
    return;
  }

  // Prepare a vector of extended points that represent all isolated vertices
  // in both input arrangements.
  typename ArrA::Vertex_const_iterator  vit1;
  typename ArrA::Vertex_const_handle    v1;
  typename ArrB::Vertex_const_iterator  vit2;
  typename ArrB::Vertex_const_handle    v2;
  const CGAL::Object                    empty_obj;
  std::vector<Ovl_point_2>              pts_vec (total_iso_verts);

  i = 0;
  for (vit1 = arr1.vertices_begin(); vit1 != arr1.vertices_end(); ++vit1)
  {
    if (vit1->is_isolated())
    {
      v1 = vit1;
      pts_vec[i++] = Ovl_point_2 (vit1->point(),
                                  CGAL::make_object (v1),
                                  empty_obj);
    }
  }

  for (vit2 = arr2.vertices_begin(); vit2 != arr2.vertices_end(); ++vit2)
  {
    if (vit2->is_isolated())
    {
      v2 = vit2;
      pts_vec[i++] = Ovl_point_2 (vit2->point(),
                                  empty_obj,
                                  CGAL::make_object (v2));
    }
  }

  // Clear the result arrangement and perform the sweep to construct it.
  arr_res.clear();

  sweep_line.sweep (xcvs_vec.begin(), xcvs_vec.end(),
                    pts_vec.begin(), pts_vec.end());
  return;
}

CGAL_END_NAMESPACE

#endif