CGAL users discussion list

["Mathieu Brédif" <>]

you cannot assign an handle to a circulator, either construct a new
circulator or affect the handle to an handle :

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

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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