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[Marco Feder <>]

I’m sorry to post again, but I’ve not been able to find the proper way to give that OutputIterator argument.

I was thinking to use std::back_inserter() like this:

std::vector<?> arr_vec;

auto my_zone = CGAL::zone(arr,my_curve,std::back_inserter(arr_vec),pl);

The issue, again, is that I don’t know what is the correct template for arr_vec. Which one should I use?

Best,

Marco

On 22 Jan 2022, at 14:04, Marco Feder <> wrote:

Thanks Efi Fogel,

I’m trying to cook a MWE to handle the situation I have in the attachment, but I have a hard time understanding how to give the OutputIterator argument to the CGAL::zone() function. 

So far I have the following snippet, which does not compile as output_it cannot be constructed. How can I define that output iterator correctly? 

#include <iostream>

#include <iterator>

#include <CGAL/Arr_segment_traits_2.h>

#include <CGAL/Arr_walk_along_line_point_location.h>

#include <CGAL/Arrangement_2.h>

#include <CGAL/Cartesian.h>

#include <CGAL/MP_Float.h>

#include <CGAL/Quotient.h>

#include <CGAL/intersections.h>

typedef CGAL::Quotient<CGAL::MP_Float> Number_type;

typedef CGAL::Cartesian<Number_type> Kernel;

typedef CGAL::Arr_segment_traits_2<Kernel> Traits_2;

typedef Traits_2::Point_2 Point_2;

typedef Traits_2::X_monotone_curve_2 Segment_2;

typedef CGAL::Arrangement_2<Traits_2> Arrangement_2;

typedef CGAL::Arr_walk_along_line_point_location<Arrangement_2> walk_pl;

int main() {

Arrangement_2 arr;

Segment_2 cv[3];

walk_pl pl(arr);

Point_2 p1(0, 0), p2(0, 4), p3(4, 0);

cv[0] = Segment_2(p1, p2);

cv[1] = Segment_2(p2, p3);

cv[2] = Segment_2(p3, p1);

CGAL::insert(arr, &cv[0], &cv[3]);

Segment_2 my_curve(Point_2(0,1), Point_2(2,2)); // curve is a segment now, it cuts the triangle

insert(arr, my_curve, pl);

// Compute the zone of the curve

std::ostream_iterator<Arrangement_2> output_it(std::cout,'\n’); // Error!  

auto my_zone = CGAL::zone(arr,my_curve, output_it,pl);

return 0;

}

Best,

Marco

On 20 Jan 2022, at 15:01, Efi Fogel <> wrote:

If you can reduce the problem to the plane (perhaps it is already in the plane), you can use the Arrangement_2 class template from the "2D Arrangement" package; see https://doc.cgal.org/latest/Arrangement_on_surface_2/index.html.

Construct an arrangement of the type of curves you are interested in, then use the CGAL::zone(c) free function to compute the zone of a given curve c; see 
https://doc.cgal.org/latest/Arrangement_on_surface_2/group__PkgArrangementOnSurface2Funcs.html#ga49aa156968945f5533a2b5d9897ca659

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

On Thu, 20 Jan 2022 at 14:27, Marco Feder <> wrote:

Dear all,

I’m completely new to CGAL, and I’d like to understand if it’s possible to perform the following task:

Consider an element T of a 2D mesh, which is cut by a curve \Gamma. Is it possible to define/get the two new elements, say T_1 and T_2, induced by the cut, as showed in the attachment?

If so, could you please point me to the right examples/pages in the manual? 

Best regards,

Marco

<cut.jpeg>

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