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[Sebastien Loriot <>]

I was about to answer the same thing as Christoper.

Best,

Sebastien

On 2/4/22 2:50 PM, Christopher Mitchell ( via cgal-discuss 
Mailing List) wrote:
> I believe the problem may be that your second polygon is oriented CW 
> instead of CCW.
>
> Sincerely,
> Christopher
>
> On Fri, Feb 4, 2022 at 8:44 AM Bob Bill < 
> <>> wrote:
>
>     Dear Sebastien,
>
>     thanks for the quick reply. I changed the code as you asked. However
>     the result is still the same. Does it work properly on your machine?
>
>     Best,
>     Bob
>
>     Il venerdì 4 febbraio 2022, 14:29:17 CET, Sebastien Loriot"
>     ( <> via cgal-discuss
>     Mailing List) < <>>
>     ha scritto:
>
>
>     Replace
>
>     typedef CGAL::Simple_cartesian<double> K;
>
>     by
>
>     #include <CGAL/Exact_predicates_exact_constructions_kernel.h>
>     typedef CGAL::Exact_predicates_exact_constructions_kernel K;
>
>     More details about why here:
>     https://www.cgal.org/FAQ.html#inexact_NT
>     
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.cgal.org_FAQ.html-23inexact-5FNT&d=DwMFaQ&c=slrrB7dE8n7gBJbeO0g-IQ&r=zsvFlmXfwI9H5xCMhxiHhQ&m=5WA2bcou1ZMQ4DLX2ggiRrrEe5CZNLQ0S7ktABh-owQLas3_p7oGcO_ORRdHWLwr&s=336f97XuAKXVN7JrE3mK_vYHoq6AXsJv3Kg_6UsR6xs&e=>
>
>     Best,
>
>     Sebastien.
>
>
>     On 2/4/22 2:26 PM, Bob Bill (
>     <> via cgal-discuss Mailing
>     List) wrote:
>      > I'm trying to find the area of the intersection between a square and
>      > another polygon. My code so far is the following (adapted from here
>      >
>     
> <https://stackoverflow.com/questions/10502672/compute-intersection-area-of-two-polygons-with-cgal
>     
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_10502672_compute-2Dintersection-2Darea-2Dof-2Dtwo-2Dpolygons-2Dwith-2Dcgal&d=DwMFaQ&c=slrrB7dE8n7gBJbeO0g-IQ&r=zsvFlmXfwI9H5xCMhxiHhQ&m=5WA2bcou1ZMQ4DLX2ggiRrrEe5CZNLQ0S7ktABh-owQLas3_p7oGcO_ORRdHWLwr&s=8-NlTFRUl4zF5FUpGJnJDmI9Ei9qujJ8SYEsZtGaF6g&e=>>,
>
>
>      > I just changed the points):
>      >
>      > #include<CGAL/Boolean_set_operations_2.h>
>      > #include<CGAL/Polygon_2.h>
>      > #include<CGAL/Polygon_2_algorithms.h>
>      > #include<CGAL/Polygon_with_holes_2.h>
>      > #include<CGAL/Simple_cartesian.h>
>      > #include<iostream>
>      >
>      > typedef CGAL::Simple_cartesian<double> K;
>      > typedef K::Point_2 Point;
>      > typedef CGAL::Polygon_2<K> Polygon_2;
>      > typedef CGAL::Polygon_with_holes_2<K> Polygon_with_holes_2;
>      >
>      > int main() {
>      > const std::vector<Point> pts{{-1, -1}, {1, -1}, {1, 1}, {-1, 1}};
>      > const std::vector<Point> pts2{{0, 1}, {0, 2}, {2, 1}, {1, 0}};
>      >
>      > Polygon_2 poly1(pts.begin(), pts.end());
>      > Polygon_2 poly2(pts2.begin(), pts2.end());
>      > std::list<Polygon_with_holes_2> polyI;
>      >
>      > CGAL::intersection(poly1, poly2, std::back_inserter(polyI));
>      >
>      > double totalArea = 0;
>      > typedef std::list<Polygon_with_holes_2>::iterator LIT;
>      > for (LIT lit = polyI.begin(); lit != polyI.end(); lit++) {
>      > std::cout << *lit << '\n';
>      > totalArea += lit->outer_boundary().area();
>      > }
>      > std::cout << "TotalArea::" << totalArea;
>      > }
>      >
>      > It compiles just fine, but then when I run it, I got the
>     following output:
>      > *3 0 1 1 1 0 1  0 *
>      > *TotalArea::0*
>      >
>      > meaning that two points are collinear and hence the area is 0.
>     What is
>      > my mistake here? I'm honestly a bit puzzled by the result and I
>     don't
>      > know how I am supposed to fix this.
>      >
>      >
>      > Best,
>      > Bob
>      >
>      >
>      >
>      >
>      >
>      >
>      >    Compute intersection area of two polygons with cgal
>      >
>      > Given the vertices of two convex polygons, what is the simplest
>     way of
>      > computing the area of their intersection ...
>
>      >
>      >
>     
> <https://stackoverflow.com/questions/10502672/compute-intersection-area-of-two-polygons-with-cgal
>     
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_10502672_compute-2Dintersection-2Darea-2Dof-2Dtwo-2Dpolygons-2Dwith-2Dcgal&d=DwMFaQ&c=slrrB7dE8n7gBJbeO0g-IQ&r=zsvFlmXfwI9H5xCMhxiHhQ&m=5WA2bcou1ZMQ4DLX2ggiRrrEe5CZNLQ0S7ktABh-owQLas3_p7oGcO_ORRdHWLwr&s=8-NlTFRUl4zF5FUpGJnJDmI9Ei9qujJ8SYEsZtGaF6g&e=>>
>      >
>      >
>      >
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