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[Peter Hachenberger <>]

Hi Amir,

you say that each cell is 2-manifold. But the whole complex is not, is it?

Peter

-----"Amir Vaxman" <> wrote: -----

To: <>
From: "Amir Vaxman" <>
Date: 03/26/2009 08:05AM
Subject: RE: [cgal-discuss] polygon_soup_to_nef3

I am looking for something which might be easier: I have a subdivision of
the space, i.e., a cell complex, in which every cell is a 2-manifold. I want
to convert it the Nef as efficiently as possible. Of course, inserting all
cells in an n-ary way is wasteful. Any suggestions?

Amir.

-----Original Message-----
From: []
Sent: Wednesday, March 25, 2009 10:53 PM
To:
Subject: [cgal-discuss] polygon_soup_to_nef3


There are a number of converters, or helper classes, that construct a
valid Nef3 from various types of geometry. (shell_to_nef_3.h for shells,
vertex_cycle_to_nef_3.h for polygons, polyhedron_3_to_nef_3.h for CGAL
polyhedrons).

I myself have written something very similar to polyhedron_3_to_nef_3 for
converting my own manifold mesh representations into Nef polyhedrons. It
is quite delicate and involves getting all the incidence references,
indices and marks correct.

Now I'm thinking of supporting a more general class of input, namely sets
of vertices and sets of polygons as references to these vertices, where
the polygons can only intersect along their edge. Any spaces enclosed by
the input polygons would be marked with mark_bounded_volumes.

This seems like a pretty obvious class of input geometry for constructing
a Nef, hence the questions:

a) Is there any plan to provide this out-of-the-box? Of course you can
achieve this with a nary_union of individual polygons, but that's very
expensive.
b) Has anybody else done this?
c) Can anybody foresee any problems I may run into here?

Regards,
Fred

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