CGAL users discussion list

["samuel kim" <>]

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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