CGAL users discussion list

[Benjamin schwarz <>]

Hello Omar and Naresh,

  I wrote a few C++ lines some times ago to convert the border of an
Alpha_shape_3 to an HDS. I cleaned my code and tried to make it more
generic, you can download it on this webpage :
http://alnitak.u-strasbg.fr/~schwarz/benjamin-schwarz-igbmc-Code-CGAL-AlphaPolyhedron.html#benjamin-schwarz-CGAL-Polyhedronification-Downloads

  The HDS allowed me to cheat and build a "combinatorially manifold"
object representing the border of the alpha shape for any alpha value
(even in Alpha_shape_3::GENERAL mode), which seems to be impossible
with the Polyhedron_3 class though it is built on a HDS.

  The Polyhedron_3 class seems to redefine its iner items (such as
Halfedges) and disallow some of their functionalities (for instance
Halfedge::set_next() is made private). The only way to modify a
Polyhedron inner HDS is thus to use a Polyhedron_builder_3, which
seems to prohibit the existence of "degenerate" cases such as two
facets with the same three corner vertices, edges sharing the same
pair of vertices, or connections of volume (or voids) through one
vertex (which occur oftenly on the alpha shape border).

             --Ben

On Fri, Apr 3, 2009 at 8:42 AM, naresh 
<>
 wrote:
> Hi Omar
>
> Thanx for help... Your code helps me
>
>
> Naresh
>
> ----- Original Message ----- From: "omar rodriguez"
> <>
> To: 
> <>
> Sent: Thursday, April 02, 2009 11:50 AM
> Subject: Re: [cgal-discuss] Alpha Shape Question
>
>
> Hello naresh
>
> you might find this of use
>
> https://lists-sop.inria.fr/sympa/arc/cgal-discuss/2009-03/msg00087.html
>
> Cheers
>
> Omar
>
> +
>
>
>
> On Wed, Apr 1, 2009 at 11:55 PM, naresh 
> <>
>  wrote:
>>
>> Hi
>>
>> Can i convert Alpha shape 3 to Polyhydron ?
>>
>> I looked at code for increment build of Polyhydron is this right method to
>> build polyhydron from Alpha shape ?
>>
>> Basically I am building 3D mesh from points and I want simplify Alpha
>> Shape
>> with edge_collapse method so i need input as Polyhydron.
>>
>> Any good method ?
>>
>> naresh
>
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