do_intersect function on arrangement with curves and x-montone curves

[Edkirito]

cgal/Arrangement_on_surface_2/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h

Line 1570 in 0ecfcb9

do_intersect(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,

I am using arrangement with bezier curve traits and there are error in do_intersect function. After check I suppose the right as below.
The argument type should be Curve_2 not X_monotone_curve_2 since they are not the same.
And a bug fix at std::get_if<Face_const_handle>.

template <typename GeometryTraits_2, typename TopologyTraits,
          typename PointLocation>
bool
do_intersect(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr,
             const typename GeometryTraits_2::Curve_2& c,
             const PointLocation& pl, std::is_same<int, double>::type)
{
  typedef GeometryTraits_2                              Gt2;
  typedef TopologyTraits                                Tt;

  // Obtain an arrangement accessor.
  typedef Arrangement_on_surface_2<Gt2, Tt>             Arr;

  // Break the input curve into x-monotone subcurves and isolated points.
  typedef Arr_traits_adaptor_2<Gt2>                     Traits_adaptor_2;

  typedef typename Gt2::Point_2                         Point_2;
  typedef typename Gt2::X_monotone_curve_2              X_monotone_curve_2;
  typedef std::variant<Point_2, X_monotone_curve_2>   Make_x_monotone_result;
  typedef typename Arr::Face_const_handle               Face_const_handle;

  const Traits_adaptor_2* traits =
    static_cast<const Traits_adaptor_2*>(arr.geometry_traits());

  std::list<Make_x_monotone_result> x_objects;
  traits->make_x_monotone_2_object()(c, std::back_inserter(x_objects));

  // Insert each x-monotone curve into the arrangement.
  for (const auto& x_obj : x_objects) {
    // Act according to the type of the current object.
    const X_monotone_curve_2* x_curve = std::get_if<X_monotone_curve_2>(&x_obj);
    if (x_curve != nullptr) {
      // Check if the x-monotone subcurve intersects the arrangement.
      if (do_intersect(arr, *x_curve, pl) == true) return true;
      continue;
    }

    const Point_2* iso_p = std::get_if<Point_2>(&x_obj);
    CGAL_assertion(iso_p != nullptr);

    // Check whether the isolated point lies inside a face (otherwise,
    // it coincides with a vertex or an edge).
    auto obj = pl.locate(*iso_p);
    if (std::get_if<Face_const_handle>(&obj) != nullptr) return true;
  }

  // If we reached here, the curve does not intersect the arrangement.
  return false;
}

[efifogel]

Hi Edkirito, You are correct. Thanks for the fix. Go ahead and create a PR, or let me know, and I'll do it. Good job, Efi ____ _ ____ _ /_____/_) o /__________ __ // (____ ( ( ( (_/ (_/-(-'_(/ _/

…

On Thu, 13 Mar 2025 at 05:44, Edkirito ***@***.***> wrote: https://github.com/CGAL/cgal/blob/0ecfcb9962b0a0618bcc324f5913b6470852656b/Arrangement_on_surface_2/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h#L1570 I am using arrangement with bezier curve traits and there are error in do_intersect function. After check I suppose the right as below. The argument type should be Curve_2 not X_monotone_curve_2 since they are not the same. And a bug fix at std::get_if<Face_const_handle>. template <typename GeometryTraits_2, typename TopologyTraits, typename PointLocation>booldo_intersect(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr, const typename GeometryTraits_2::Curve_2& c, const PointLocation& pl, std::is_same<int, double>::type) { typedef GeometryTraits_2 Gt2; typedef TopologyTraits Tt; // Obtain an arrangement accessor. typedef Arrangement_on_surface_2<Gt2, Tt> Arr; // Break the input curve into x-monotone subcurves and isolated points. typedef Arr_traits_adaptor_2<Gt2> Traits_adaptor_2; typedef typename Gt2::Point_2 Point_2; typedef typename Gt2::X_monotone_curve_2 X_monotone_curve_2; typedef std::variant<Point_2, X_monotone_curve_2> Make_x_monotone_result; typedef typename Arr::Face_const_handle Face_const_handle; const Traits_adaptor_2* traits = static_cast<const Traits_adaptor_2*>(arr.geometry_traits()); std::list<Make_x_monotone_result> x_objects; traits->make_x_monotone_2_object()(c, std::back_inserter(x_objects)); // Insert each x-monotone curve into the arrangement. for (const auto& x_obj : x_objects) { // Act according to the type of the current object. const X_monotone_curve_2* x_curve = std::get_if<X_monotone_curve_2>(&x_obj); if (x_curve != nullptr) { // Check if the x-monotone subcurve intersects the arrangement. if (do_intersect(arr, *x_curve, pl) == true) return true; continue; } const Point_2* iso_p = std::get_if<Point_2>(&x_obj); CGAL_assertion(iso_p != nullptr); // Check whether the isolated point lies inside a face (otherwise, // it coincides with a vertex or an edge). auto obj = pl.locate(*iso_p); if (std::get_if<Face_const_handle>(&obj) != nullptr) return true; } // If we reached here, the curve does not intersect the arrangement. return false; } — Reply to this email directly, view it on GitHub <#8782>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABVBNOFA2ACQVEXM2ZEMTBT2UD5JPAVCNFSM6AAAAABY5FC73WVHI2DSMVQWIX3LMV43ASLTON2WKOZSHEYTKNZUGUYTAMQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***> [image: Edkirito]*Edkirito* created an issue (CGAL/cgal#8782) <#8782> https://github.com/CGAL/cgal/blob/0ecfcb9962b0a0618bcc324f5913b6470852656b/Arrangement_on_surface_2/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h#L1570 I am using arrangement with bezier curve traits and there are error in do_intersect function. After check I suppose the right as below. The argument type should be Curve_2 not X_monotone_curve_2 since they are not the same. And a bug fix at std::get_if<Face_const_handle>. template <typename GeometryTraits_2, typename TopologyTraits, typename PointLocation>booldo_intersect(Arrangement_on_surface_2<GeometryTraits_2, TopologyTraits>& arr, const typename GeometryTraits_2::Curve_2& c, const PointLocation& pl, std::is_same<int, double>::type) { typedef GeometryTraits_2 Gt2; typedef TopologyTraits Tt; // Obtain an arrangement accessor. typedef Arrangement_on_surface_2<Gt2, Tt> Arr; // Break the input curve into x-monotone subcurves and isolated points. typedef Arr_traits_adaptor_2<Gt2> Traits_adaptor_2; typedef typename Gt2::Point_2 Point_2; typedef typename Gt2::X_monotone_curve_2 X_monotone_curve_2; typedef std::variant<Point_2, X_monotone_curve_2> Make_x_monotone_result; typedef typename Arr::Face_const_handle Face_const_handle; const Traits_adaptor_2* traits = static_cast<const Traits_adaptor_2*>(arr.geometry_traits()); std::list<Make_x_monotone_result> x_objects; traits->make_x_monotone_2_object()(c, std::back_inserter(x_objects)); // Insert each x-monotone curve into the arrangement. for (const auto& x_obj : x_objects) { // Act according to the type of the current object. const X_monotone_curve_2* x_curve = std::get_if<X_monotone_curve_2>(&x_obj); if (x_curve != nullptr) { // Check if the x-monotone subcurve intersects the arrangement. if (do_intersect(arr, *x_curve, pl) == true) return true; continue; } const Point_2* iso_p = std::get_if<Point_2>(&x_obj); CGAL_assertion(iso_p != nullptr); // Check whether the isolated point lies inside a face (otherwise, // it coincides with a vertex or an edge). auto obj = pl.locate(*iso_p); if (std::get_if<Face_const_handle>(&obj) != nullptr) return true; } // If we reached here, the curve does not intersect the arrangement. return false; } — Reply to this email directly, view it on GitHub <#8782>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABVBNOFA2ACQVEXM2ZEMTBT2UD5JPAVCNFSM6AAAAABY5FC73WVHI2DSMVQWIX3LMV43ASLTON2WKOZSHEYTKNZUGUYTAMQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Edkirito]

Hi Edkirito,
You are correct.
Thanks for the fix.
Go ahead and create a PR, or let me know, and I'll do it.
Good job,
Efi

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/_____/) o /_________ __ //
(____ ( ( ( (/ (/-(-'_(/
_/
…

Sure. You can do it. Thanks.

[efifogel]

Just did ____ _ ____ _ /_____/_) o /__________ __ // (____ ( ( ( (_/ (_/-(-'_(/ _/

…

On Sat, 15 Mar 2025 at 05:07, Edkirito ***@***.***> wrote: Hi Edkirito, You are correct. Thanks for the fix. Go ahead and create a PR, or let me know, and I'll do it. Good job, Efi ------------------------------ /_____/*) o /*_________ __ // (____ ( ( ( (*/ (*/-(-'_(/ _/ … <#m_4102398309624879806_> Sure. You can do it. Thanks. — Reply to this email directly, view it on GitHub <#8782 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABVBNOFKNLWLT36UYY36BAL2UOKNRAVCNFSM6AAAAABY5FC73WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDOMRWGE3DCNZTGI> . You are receiving this because you commented.Message ID: ***@***.***> [image: Edkirito]*Edkirito* left a comment (CGAL/cgal#8782) <#8782 (comment)> Hi Edkirito, You are correct. Thanks for the fix. Go ahead and create a PR, or let me know, and I'll do it. Good job, Efi ------------------------------ /_____/*) o /*_________ __ // (____ ( ( ( (*/ (*/-(-'_(/ _/ … <#m_4102398309624879806_> Sure. You can do it. Thanks. — Reply to this email directly, view it on GitHub <#8782 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABVBNOFKNLWLT36UYY36BAL2UOKNRAVCNFSM6AAAAABY5FC73WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDOMRWGE3DCNZTGI> . You are receiving this because you commented.Message ID: ***@***.***>