CGAL users discussion list

[Camille Wormser <>]

> the tree.number_of_intersected_primitives(Segment) gives me 5
> intersections. But if I use the code to test what type of objects  
> are. only 3
> are Point_3. What are the other 2?

Hi Roberto,
This is a typical robustness issue: I guess you use the  
exact_predicates_inexact_constructions kernel. In such a case, the  
do_intersect predicate used to answer the number_of_intersections  
query is exact. Hence the answer 5. On the other hand, the  
intersection constructions are not, and I suspect that they simply do  
not find any intersection for the two missing cases (I assume from  
your message that the code did not find any segment intersection).

Of course, it would be better if the predicates and the constructions  
were consistent in the exact_predicates_inexact_constructions kernel  
(i.e. Always returning a non empty construction if the predicate said  
so). This is on some todo-list, but it is a delicate question. (note  
that it is not really AABB-tree related)

Best
--
Camille