CGAL users discussion list

[Mael <>]

Hello,

Do you really care for the primitive, or just the neighboring faces? If you just want the neighboring faces, and assuming your primitive is AABB_face_graph_triangle_primitive, the primitive ID is a boost::graph_traits<Surface_mesh>::face_descriptor (i.e. Surface_mesh::Face_index) and you can use BGL-like functions provided by CGAL such as CGAL::faces_around_face:

face_descriptor fd = p_id;
for(face_descriptor neigh_fd : CGAL::faces_around_face(halfedge(fd, sm), sm) // sm is your surface mesh
{
  etc
}

See the package BGL for a lot of convenient functions (it requires a data structure to fit a certain interface, which CGAL::Surface_mesh does using the 'graph_traits' interface).

Best,
Mael

On 16/05/2019 01:57, Rash wrote:

Hi people,

I wrote a small raytracer (with CGAL::Surface_mesh<Point> Mesh) with tree acceleration in cgal. I would like to find all neighbours of a hit primitive.

Ray_intersection hit = tree.first_intersection(rays[y][x]);

if(hit)
{
    const Point& point =  boost::get<Point>(hit->first);
    const Primitive_id& primitive_id = boost::get<Primitive_id>(hit->second);
    //i need the neighbours of the hit primitive
}

How do I this? I found this documentation but it seems to work only for points not primitives:

https://doc.cgal.org/latest/Spatial_searching/index.html

And it searches for its euclidan distance not for being connected together.

Is there something like:

std::vector<Primitive_id&> ids = getNeighoursOfPrimive(primitive_id);


Like I said I am using CGAL::Surface_mesh<Point> Mesh for my mesh and their is only one mesh in the scene.

Kind regards
Rashid