CGAL users discussion list

Hi,
I computed the intersection points of a ray and a 3D object represented as
a 3D complex (for example a tetrahedron mesh in 3D mesh generation).  I
combined a 3D mesh generation procedure with an AABB tree. My query object
is a line with fixed direction and crossing a vertex of the mesh (I
consider parallel rays crossing each vertex for different intersection
queries) and I use a kind of AABB_primitive, such as Datum is Triangle_3
and Id is Tr::Facet_finite_iterator. Thus I can get back the triangulation
facet from the intersected Object_and_primitive_id.
My problem is that, for each line which crosses a vertex, I need to
keep/control just the intersection point "before" this vertex. I try to do
this by defining this point for each vertex as the point lying in the
facet opposite to the vertex (that is the index defining the facet
coincides with the index of the vertex ). I would expect to select in this
way for each vertex just the two intersected facets opposite to the vertex
and, sorting the two corresponding intersection points, to find the
intersection point "before" the vertex. Conversely I detect a lot of
intersections when applying this procedure. Is the adopted criterion
wrong?
Moreover I'm setting the condition c3t3.is_in_complex(cell) for the cell
containing the intersected primitive to be assured of getting facets
belonging the 3D complex. Does it correspond to get facets both inside the
volume and on the surface or surface facets are excluded?

Thanks in advance for any suggestions!