CGAL users discussion list

[Lefieux Adrien <>]

Thank you Sebastien for your answer.

Actually, I tried my code alse with segment primitives instead of 
triangle primitives but it appears that every polyhedron in the tree has 
its own segments so I get again multiple identical solutions. Of course, 
I can write a function to check how many intersection are unique but I 
wondered if there are any approaches in CGAL and where I can find them.

In the end, I would like to consider a triangulation of a domain in R^3 
and say to get its intersection with a plane. It is likely that the 
plane is going to intersect with a ridge and this ridge is possibly 
common to many polyhedra. Hence I would like to get only one 
intersection because the common ridge can be uniquely defined.

Thank you,

Adrien


Le 11/20/12 5:41 AM, Sebastien Loriot (GeometryFactory) a écrit :
> The result is correct, it reports 3 intersections because 3 triangles
> are intersected, and the primitive is a triangle.
>
> They are many solutions to avoid that but it depends on what is your 
> final goal.
>
> Sebastien.
>
>
> On 11/20/2012 02:05 AM, alef wrote:
> > Hello everybody,
> >
> > Problem: My code computes multiple identical intersections of a 
> > segment with
> > a polyhedron.
> >
> > I try to solve the following problem from
> > examples/AABB_tree/AABB_polyhedron_facet_intersection_example.cpp
> >
> > The kernel is defined exactly as follow:
> > /typedef CGAL::Gmpq FT;
> > typedef CGAL::Lazy_exact_nt<FT>  RT;
> > typedef CGAL::Simple_cartesian<RT>  K;/
> >
> > the tetrahedron is defined by:
> > /Point p1(1.0, 0.0, 0.0);
> > Point q1(0.0, 1.0, 0.0);
> > Point r1(0.0, 0.0, 1.0);
> > Point s1(0.0, 0.0, 0.0);
> > polyhedron.make_tetrahedron(p1, q1, r1, s1);/
> >
> > The segment is defined by:
> > /Point a(0.25, 0.25, 1.0);
> > Point b(-0.25, -0.25, 1.0);
> > Segment segment_query(a,b);/
> >
> > The intersection is performed by:
> > /std::vector<Object_and_primitive_id>  intersections;
> > tree.all_intersections(segment_query, 
> > std::back_inserter(intersections));/
> >
> > The result should be: 1 intersection at (0,0,1).
> >
> > But the it gives me 3 intersections each one at (0,0,1). Is it normal 
> > or is
> > it a bug? if it is a bug then what could be the solution?
> >
> > Cordially,
> > Adrien
> >
> >
> >
> > --
> > View this message in context: 
> > http://cgal-discuss.949826.n4.nabble.com/AABB-tree-all-intersections-Multiple-identical-intersections-tp4656289.html
> > Sent from the cgal-discuss mailing list archive at Nabble.com.