CGAL users discussion list

[Sebastien Loriot <>]

For sure but if you get let say a quad you need to add its area.

Do you seen what I mean?

Best,

Sebastien.

On 7/26/22 18:08, Marco Feder ( via cgal-discuss Mailing 
List) wrote:
> Dear Sebastien,
>
> That is precisely what I did in the GitHub gist I linked in my post, isn’t it 
> ?
>
> Best,
> Marco
>
> > On 26 Jul 2022, at 17:08, Sebastien Loriot <> wrote:
> >
> > The intersecton of a triangle with a tet is not always a triangle, it is
> > a polygon,
> >
> > Doc says:
> > |Type1  | Type2 |Return Type: T...|
> > |Triangle_3 Tetrahedron_3 |     Point_3, or Segment_3, or Triangle_3, or 
> > std::vector < Point_3 > |
> >
> > https://doc.cgal.org/latest/Kernel_23/group__intersection__linear__grp.html
> >
> >
> > So it is most likely you miss some polygons.
> >
> > Best,
> >
> > Sebastien.
> >
> > On 7/20/22 10:44, Marco Feder ( via cgal-discuss Mailing List) 
> > wrote:
> > > Dear all,
> > > I have two cubes (they’re coming from two cells of a 3D finite element mesh) 
> > > and a square (a 2D object) between the two, intersecting both of them. I 
> > > triangulated each cube with a Triangulation_3, and the square with a 
> > > Delaunay_triangulation_2.
> > > To compute the intersection of the square with the first cube, I do the 
> > > following: I loop over all tets of the triangulated cube, and for each 
> > > Tetrahedron I compute the intersection with a Triangle_3 coming from the 
> > > triangulated 2D square. Oftentimes I have correct results, but in some 
> > > scenarios I observe inaccurate results.
> > > For instance: for each cube, I computed the area of the part of square inside 
> > > it. The sum of these two areas should be precisely equal to the area of the 
> > > square (it is exactly *0.136900*), but it’s not. In particular, the first 
> > > area is *0.0237738*, and the second *0.0948123. *Then the sum is *not 
> > > 0.136900.*
> > > The following GitHub gist shows this: 
> > > https://gist.github.com/fdrmrc/49f397a5f72a7a00b1dfb992ab7babe1 
> > > <https://gist.github.com/fdrmrc/49f397a5f72a7a00b1dfb992ab7babe1> . The 
> > > output is the area of the intersection of the square with the second cube. To get 
> > > the first area, change at line 52 /pts_second_hex /with /pts_first_hex./
> > > I can’t spot what is going wrong here.
> > > Best,
> > > Marco
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