CGAL users discussion list

[Daniel Duque <>]

Hello,

You may consider the move function. It should be inherited from 
Triangulation_2.

For some reason, this function is not documented, but it's right there in the 
code. If you have a look, you can see that the process is indeed not that 
simple ( include/CGAL/Triangulation_2.h )

BTW, the fact that move is not documented anywhere is a bit unsettling for 
me, 
since I've been using it quite a lot (actually the Delaunay move(), which is 
redefined, not just inherited). In my case, it is because I am using a loop 
over vertices, and moving them. An insert + removal would modify the loop 
iterator.

Best,

Daniel



On Wednesday 07 April 2010 16:42:47 pierre wrote:
> Well, sorry for being so confusing (and for the typo in your name).
>
> To make things simple, I must keep my Vertex_handles untouched at all cost.
>
> Actually, all I need is to find the set of proper tests for detecting and
> preventing any combinatorial changes from happening if I move my vertex so
> that I can backtrack.
> But I just cannot seem to have those tests right. I must forget something
> ... :S
>
> On Wed, Apr 7, 2010 at 4:26 PM, pierre 
> <>
>  wrote:
> > Hi Sebastian,
> >
> > Actually I need to keep my Vertex_handles intact.
> >
> > This algorithm is basically some kind of a greedy triangulation growing
> > thing (with a lot of computations going around)
> > and I need to keep track of the recently-added vertices so that I can
> > process them later on. I typically store the to-be-processed
> > Vertex_handles in a priority_queue from which I pop the vertex to
> > consider.
> >
> >
> > Am afraid that using remove(V) and insert(P) will generate another handle
> > and compromise the validity of the pointers stored in my
> > queue.
> > But thanks for your quick reply anyway. :)
> >
> >    Pierre.
> >
> >
> >
> > On Wed, Apr 7, 2010 at 4:20 PM, Sebastien Loriot (GeometryFactory) <
> >
> > >
> >  wrote:
> >> Hello,
> >>
> >> have you tried to use functions
> >> remove(Vertex_handle v) and insert(Point p)
> >> to mimic the move? is it to slow?
> >>
> >> S.
> >>
> >> piR wrote:
> >>> Hi everyone,
> >>>
> >>> This is I guess a pretty stupid question but I just cannot seem to make
> >>> it
> >>> work properly.
> >>> I need to move a point within a triangulation. For that aim, I use the
> >>> Vertex_handle->setpoint(Point) function a bit
> >>> recklessly.
> >>> Usually the new positions are almost the same as the previous ones (it
> >>> is a
> >>> relaxation step), so it seems to work fine.
> >>> But of course, since I do not properly check whether the predicates are
> >>> still verified after the move, there are cases where my triangulation
> >>> gets
> >>> corrupted.
> >>>
> >>> Would you mind helping me doing this properly?
> >>> I tried to backtrack according to the result of the is_valid()
> >>> functions, but to no avail.
> >>> I swear I looked around, and only found a solution for a more
> >>> restrictive Delaunay triangulation somewhere.
> >>> Am a total CGAL newbie and this needs to work asap.
> >>> MANY THANKS!
> >>
> >> --
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-- 
http://debin.etsin.upm.es/~daniel