CGAL users discussion list

[Peter Hachenberger <>]

The function is only in CGAL 3.3.1. Just call 

N = N.intersection(Plane_3(a,b,c,d));

Peter

On Wed, 2008-01-30 at 01:52 -0800, Stephen Wong wrote:
> ________________________________________
> From: Peter Hachenberger 
> []
> Sent: Wednesday, January 30, 2008 1:31 AM
> To: 
> 
> Hi Peter,
> 
> Thank you for your quick response. You are absolutely right - I am looking 
> at performing an intersection with a half-plane.  Can you please let me 
> know of this undocumented function? The fact that I won't need to switch to 
> a another (slower) kernel for this functionality is pleasing to hear!
> 
> Regards,
> 
> Stephen
> 
> Subject: Re: [cgal-discuss] [Nef_polyhedron_3] Creation of half-planes
> 
> Hi Stephen,
> 
> I somehow neglected the Extended_cartesian kernel for a while and
> therefore it is not compiling at the current release. Usually nobody
> uses the extended kernels, but recently somebody wanted to work with the
> Extended_cartesian_kernel and I fixed it. So, if you want to use it, I
> can send you 2-3 updated files that will fix the problems.
> 
> Before you do that, I want to find out, whether you really need an
> extended kernel. They are pretty slow and not often needed. In the
> latest release there is an undocumented function that allows
> intersection with a halfspace without constructing the halfspace
> explicitly. If that is the only reason why you need halfspaces, then you
> don't need the extended kernels.
> 
> Thanks for the note on the Extended_XXX_3 kernels. That's an error. In
> the beginning I thought I need separate kernels for different
> dimensions, but that is not true. These kernels do not exist. Use
> Extended_homogeneous and Extended_cartesian.
> 
> Peter
> 
> On Tue, 2008-01-29 at 18:03 -0800, Stephen Wong wrote:
> > Hi there,
> >
> >
> >
> > Another quick question for you guys.  In Section 18.5.1 in the
> > documentation where a Extended_homogeneous<Gmpz> kernel is used to
> > demonstrate construction of Nef_polyhedron_3 using a half-plane
> > definition, I tried the same with Extended_cartesian<Gmpq> but this
> > did not work – compiler errors resulted.  This documentation is found
> > here:
> >
> >
> >
> > http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Nef_3/Chapter_main.html#Subsection_18.5.1
> >
> >
> >
> > It is also note worthy to mention that in the reference to
> > Nef_polyhedron_3, there is a reference to a Extended_homogeneous_3
> > (presumably 3D version of the Extended homogeneous) and
> > Extended_cartesian_3, but none of these two kernels seem to actually
> > exist.  In the example of 18.5.1, the Extended_homogeneous (w/o “_3”)
> >  is used to initialize a 3D plane in Nef_polyhedron_3 with success.
> > What am I not doing correctly to obtain the same results with
> > Extended_cartesian<Gmpq>?
> >
> >
> >
> > Thanks,
> >
> >
> >
> > Stephen
> >
> >
> 
> --
> You are currently subscribed to cgal-discuss.
> To unsubscribe or access the archives, go to
> https://lists-sop.inria.fr/wws/info/cgal-discuss
>