CGAL users discussion list

[Yaoyu Hu <>]

Hi all,

I am looking at the example code here https://doc.cgal.org/latest/AABB_tree/AABB_tree_2AABB_ray_shooting_example_8cpp-example.html 

which is an AABB ray shooting example. 

I was wondering that what should I do if I want to get the first intersection facet from the ray shooting computation? 

When I was trying to find the answer from other examples in the documentation, I got lost. I have the feeling that it might have something to do with "datum and reference id" or the underlying CGAL::AABB_face_graph_triangle_primitive<> data structure. But I failed to understand how to correctly and effectively use them.

My current understanding is using first_intersection_primitive() to get some sort of "Primitive_id". Then use the id to get access to the actual geometry element such as a facet. Or the first_intersection() function, which seems to return the primitive id and an intersection object at the same time. However, apart from the above thoughts, I did not find a concrete example illustrating the correct usage for accessing the facet which is intersecting with the query ray.

Any help is appreciated. Thanks! 

Yaoyu