CGAL users discussion list

samuel kim wrote:
> Hi Mathieu,
>
> I tried both as you said, but the same error comes out. 
>
> Sam
> -----Original Message-----
> From: 
>
>  
> [mailto:]
>  On Behalf Of Mathieu
> Bredif
> Sent: Wednesday, May 07, 2008 3:13 PM
> To: 
>
> Subject: Re: [cgal-discuss]To understand half edge data structure
>
> you cannot assign an handle to a circulator, either construct a new
> circulator or affect the handle to an handle :

the same explanation is still valid, but:

> Halfedge_around_facet_circulator
> pHalfedge_new(pHalfedge->prev()->opposite());

there is a copy-paste mistake here, the explanation above allows to 
easily fix it... :
Halfedge_handle
pHalfedge_new(pHalfedge->prev()->opposite());

> or
> Halfedge_handle pHalfedge_new = pHalfedge->prev()->opposite();

this should work

        Monique Teillaud
> Mathieu
>
>
>
> > On Wed, May 7, 2008 at 2:57 PM, samuel kim 
> > <>
> >  wrote:
> > > Hi Mathieu and Janssens,
> > >
> > >  Thank you very much for your reply, I think you are right. So I tried
>
> it but
>
> > >  an error coming out.
> > >  When I run as the below,
> > >
> > >  Halfedge_around_facet_circulator pHalfedge = pFacet->facet_begin();
> > >  pHalfedge = pHalfedge->prev()->opposite();
> > >
> > >  error C2679: binary '=' : no operator found which takes a right-hand
>
> operand
>
> > >  of type 'CGAL::CGALi::In_place_list_iterator<T,Alloc>' (or there is no
> > >  acceptable conversion)
> > >
> > >  Would you mind if I ask you one more time How can I solve this?
> > >
> > >  Samuel
> > >
> > >  -----Original Message-----
> > >  From: 
> >
> >  
> > [mailto:]
> >  On Behalf Of
>
> Mathieu
>
> > >  Bredif
> > >  Sent: Wednesday, May 07, 2008 2:34 PM
> > >  To: 
> >
> > >  Subject: Re: [cgal-discuss]To understand half edge data structure
>
> (VERY
>
> > >  IMPORTANT)
> > >
> > >  Hi,
> > >  the facet_begin() halfedge is arbitrary, your mistake is to assume
> > >  that facet2->facet_begin() is a particular halfedge handle.
> > >  My advice is to stay with halfedges without using the intermediate
>
> face
>
> > >  handles:
> > >
> > >  A C = AB->prev()->opposite()
> > >  A'C = AC->next_on_vertex() // or more verbosely AB->next()->opposite()
> > >
> > >  Mathieu
> > >
> > >  On Wed, May 7, 2008 at 1:58 PM, samuel kim 
> > <>
>
> wrote:
>
> > >  > Hi all,
> > >  >
> > >  >  I am struggling in an implementation with the half edge data
>
> structure.
>
> > >  What I want to do is to travel the triangles from triangle# 1 to
>
> triangle# 3
>
> > >  as shown at attached picture. For this, I read CGAL document and
>
> implemented
>
> > >  based on what I understood. But result is not going to triangle# 3 but
>
> going
>
> > >  back to triangle# 1 from triangle#2. The below is the source code I
>
> tried.
>
> > >  >
> > >  >  Facet_handle hf_new;
> > >  >  Facet_iterator pFacet = facets_begin();
> > >  >  Halfedge_around_facet_circulator pHalfedge = pFacet->facet_begin();
>
> //
>
> > >  expecting to get the handle of half_edge1 on triangle#1
> > >  >
> > >  >  hf_new = pHalfedge->prev()->opposite()->facet(); // expecting to
>
> get the
>
> > >  handle of facet of triangle#2
> > >  >  pHalfedge = hf_new->facet_begin(); // expecting to get the handle
>
> of
>
> > >  half_edge2 in the triangle#2
> > >  >
> > >  >  hf_new = pHalfedge->next()->opposite()->facet(); // expecting to
>
> get the
>
> > >  handle of facet of triangle#3
> > >  >  pHalfedge = hf_new->facet_begin(); // expecting to get the handle
>
> of
>
> > >  half_edge2 on the triangle#3
> > >  >
> > >  >
> > >  >  If I did as the above, the handle of facet was that of triangle#1.
>
> So I
>
> > >  want to ask you a question, when I do this,
> > >  >         hf_new = pHalfedge->prev()->opposite()->facet(); //
>
> expecting to
>
> > >  get the handle of facet of triangle#2
> > >  >         pHalfedge = hf_new->facet_begin(); // expecting to get the
>
> handle
>
> > >  of half_edge2 in the triangle#2
> > >  >  Which edge handle should be returned in triangle#2?
> > >  >  And what is the base rule to get to know the exact pointer of the
>
> handle
>
> > >  of half_edge data structure whenever travel triangles? Because I have
>
> tried
>
> > >  many times, and found that the pointer of handle of half_edge data
>
> structure
>
> > >  was varying at each triangle which was not expectable.
> > >  >
> > >  >  Thank you for your help.
> > >  >
> > >  >  Samuel
> > >  >
> > >  >
> > >  >  --
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