CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

The type of id is

std::vector<Triangle>::iterator

so to get the index you can do something like:

std::vector<Triangle> triangles;
....
std::size_t index_in_vector = std::distance(triangles.begin(),id);
assert( triangles[index_in_vector == *id );

Sebastien.

On 10/20/2012 08:51 PM, gg++ wrote:
> Hi,
>
> I've built an AABB tree from a vector of Triangle_3's (named
> triangles_vector) that represent a triangular mesh. For a given Ray_3 query,
> I'd like to find the intersected triangle in the tree/mesh that is closest
> to the source point of the ray, and then I need to find the location/index
> of that triangle in the vector of triangles I originally used to build the
> AABB tree.
>
> Basically, each triangle in the mesh has a corresponding number identifier
> that I use for bookkeeping, and for now I'm using the index location of the
> triangle in the original triangle vector as that number, i.e., Triangle 724
> can be found at triangles_vector[724].
>
> Since I know the AABB tree doesn't provide any functions for finding the
> first intersected triangle with respect to the query source point as I need,
> I was going to use:
>
>
> std::vector<Primitive_id>  primitives;
> tree.all_intersected_primitives( Ray_3, std::back_inserter(primitives));
>
>
> This would give me a vector of primitive ID's, but I really don't know what
> a Primitive_id is or how to use it to find the corresponding triangles in
> the original triangles_vector that I used to build the tree. If I could find
> the original triangles, I could run distance queries to find the closest to
> the ray source and then keep track of what triangles got hit by the ray.
>
> My tree has the following setup:
>
> typedef CGAL::Simple_cartesian<double>  K;
> typedef std::vector<Triangle>::iterator Iterator;
> typedef CGAL::AABB_triangle_primitive<K, Iterator>  Primitive;
> typedef CGAL::AABB_traits<K, Primitive>  AABB_triangle_traits;
> typedef CGAL::AABB_tree<AABB_triangle_traits>  Tree;
> typedef Tree::Primitive_id Primitive_id;
>
> Can someone please point me in the right direction? As you probably already
> figured out, I have very limited experience with C++ and even less posting
> to technical forums, so please explain it to me like I'm a two year-old
>
> Thank you,
>
> Grant
>
>
>
>
>
> --
> View this message in context: 
> http://cgal-discuss.949826.n4.nabble.com/Identifying-Intersected-Triangles-in-AABB-Tree-tp4656054.html
> Sent from the cgal-discuss mailing list archive at Nabble.com.