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["Max" <>]

Hello Peter

Thank you so much for your continuous help. 

B/Rgds
Max

----- Original Message ---- 
From: Peter Hachenberger
To: 

Sent: 2008-01-10 22:55:20
Subject: Re: Re: [cgal-discuss][Nef_polyhedron] How to 
convertaNef_polyhedron_3 into a Nef_polyhedron_2 if meaningful

>
I already gave you the answer:

store the points of the Nef_3 and then pass those points to the
constructor of the Nef_2

That should also work with Polygon/Polygon_with_hole in some way.

Peter

On Wed, 2008-01-09 at 10:01 +0800, LoadCom wrote:
> Hello Peter,
> 
> Thanks for your quick response. It's very helpful indeed.
> 
> It's not a surprise to know that the designer of CGAL has never thought 
> of such a *strange* conversion. Perhaps it's too wild. :-)
> 
> From your reply, it seems that it's still possible (I mean not so hard)
> to write some code to get such a conversion.
> 
> At the present time, efficiency is probably not a main problem for me. The 
> result I desired is somthing that similar in topology to a Nef_2, or 
> perferrably,
> in terms of a Polygon_with_hole data structure. With that, I can get to 
> calculte some geometric properties of this polygon, including center of 
> area,
> moment of inertia, and so on.
> 
> If possible, could you please give me some more detailed instruction with
> which I could accomplish that needs?
> 
> I really appreciat the help you've given me.
> 
> B/Rgds
> Max
> 
> ----- Original Message ---- 
> From: Peter Hachenberger
> To: 
> 
> Sent: 2008-01-08 18:38:41
> Subject: Re: [cgal-discuss][Nef_polyhedron] How to convert 
> aNef_polyhedron_3 into a Nef_polyhedron_2 if meaningful
> 
> >
> Hi Max,
> 
> we never really thought about this conversion. So, we don't have it. An
> easy thing to do is just to store the points of the Nef_3 and then pass
> those points to the constructor of the Nef_2. I guess that any
> conversion tool I could write would not be more efficient than that. The
> main disadvantage to a real conversion is, that you loose the marks. The
> constructor does not allow you to choose for every edge whether it is
> selected or not. Does that help you?
> 
> Peter
> 
> On Mon, 2008-01-07 at 15:38 +0800, LoadCom wrote:
> > Hello,
> > 
> > Suppose I have a closed Nef_polyhedron_3 N, and I construct a plane with 
> > Nef_polyhedron_3 in this manner
> > 
> > Nef_polyhedron_3 N; // closed
> > 
> > // now constructing a plane Nef
> > Plane_3 pl(1, 1, 1, 0);
> > Nef_polyhedron_3 N_plane(Nef_polyhedron_3(pl) * !Nef_polyhedron_3(pl, 
> > Nef_polyhedron::EXCLUDED));
> > 
> > // Now I intersect these 2 Nef:
> > 
> > Nef_polyhedron_3 N_res = N * N_plane;
> > 
> > Now N_res is actually a Nef_polyhedron_2, but is there a way to convert 
> > it into a Nef_polyhedron_2
> > and then explore it accordingly?
> > 
> > Thanks in advance.
> > Max
> > 
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