CGAL users discussion list

["Tardugno, Angelo" <>]

Thanks very much Andreas, actually I quite like how this thing works, now 
that I actually know how it works.
Gonna try first thing tomorrow morning.

Thanks

Angelo


-----Messaggio originale-----
Da: Andreas Fabri 
[mailto:]
Inviato: mar 29/05/2007 19.58
A: 

Oggetto: Re: [cgal-discuss] How to excract poles
 
Hi Angelo,

An OutputIterator is something that points to a position
in memory where one can write to, and which can advance
to the next position.

So you take a container of the right type, say
std::list<Cell_handle> cells;


and by calling

t.incident_cells(v, std::back_inserter(cells));

the neighbor cells are now in the list.

std::back_inserter generates an iiterator object which holds
a reference to the list cells, and when one writes to it, it
calls  cells.push_back(..).

The beauty of this is that it works with whatever
output iterator, and there is no need to first
write to the container we might have hardwired
and then you have to copy it to the container
where you really want it to be.

And the design idea comes from the STL, so blame
them if you don't like such a design ===:>-

andreas


Tardugno, Angelo wrote:
> The poles are defined as the furthest voronoi vertices, so they're a 
> subset of the voronoi vertices. My problem is how to implement the idea 
> you've just exposed. I've found this on CGAL-manual
>  
> / /
> 
> /template /</class OutputIterator/>
> 
> / /
> 
> /OutputIterator t.incident cells( Vertex handle v, OutputIterator cells)/
> 
> Copies the /Cell handle/s of all cells incident to /v /to the output 
> iterator
> 
> / /
> 
> /cells/. If /t/./dimension() /< 3, then do nothing. Returns the 
> resulting output
> 
> iterator.
> 
>  
> 
> but I have no idea of what an OutputIterator is. At the moment I'm 
> thinking of doing an iteration on the finite vertices of the 
> triangulation (using a Finite Vertices Iterator) and for each of the 
> vertices find the incident cells and calculate their dual (these are the 
> Voronoi vertices corresponding to the sample I'm considering). Among 
> these vertices I then have to find the two furthest. Anyway, at the 
> moment I'm stuck at the point of finding the incident cells since I have 
> no idea of how using the incident_cells method.
> 
> Anyone can help me?!
> 
> Thanks
> 
>  
> 
> Angelo Tardugno
> 
> / /
> 
> /Precondition/: /v /6= /Vertex handle()/, /t/./is vertex(v)/.
> 
> 
> ------------------------------------------------------------------------
> *From:* Jingyi Jin 
> [mailto:]
> *Sent:* 29 May 2007 16:35
> *To:* 
> 
> *Subject:* Re: [cgal-discuss] How to excract poles
> 
> Hi Angelo,
>  
> Is it true that the poles are always Voronoi vertices? If so, you can 
> get all incident Delaunay facets to a vertex v, compute the dual of 
> those facets, which are vertices of Voronoi cell of v. Loop over those 
> vertices, and the furthermost one is the pole.
>  
> This is my thought, I am not sure if I interpreted things correctly.
>  
> Jingyi
> 
>  
> On 5/29/07, *Tardugno, Angelo* 
> <
>  
> <mailto:>>
>  wrote:
> 
>     Hi CGAL experts,
>      
>     I have to extract the poles of each Voronoi cell of a cloud of 3D
>     point. Can anybody can give me an hint of how this can be done with
>     CGAL? I thought that I have to consider each Delaunay vertex and
>     then, somehow, bulid its correspondent Voronoi cell and then
>     consider the farthest vertices of this cell. Still I don't know
>     where to begin. Thank You for your help
>      
>     Angelo Tardugno
> 
> 

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