CGAL users discussion list

["samuel kim" <>]

I found a simple solution for my case, just changed the type of pHalfedge
from Halfedge_around_facet_circulator  to Halfedge_handle, then it works
fine for the line,

pHalfedge = pHalfedge->prev()->opposite()

Thank you though.

Samuel

-----Original Message-----
From: samuel kim 
[mailto:]
 
Sent: Wednesday, May 07, 2008 3:57 PM
To: 

Subject: RE: [cgal-discuss]To understand half edge data structure

Hi Mathieu,

I am sorry that there was a mistake. It works now fine. Thanks. But is there
any way to give the handle back to pHalfedge? , because I need to use
pHalfedge continuously in my program. 

pHalfedge_new = pHalfedge->prev()->opposite() then how can I give the new
handle back to pHalfedge?
pHalfedge = ?

Thank you in advance.

Samuel


-----Original Message-----
From: samuel kim 
[mailto:]
 
Sent: Wednesday, May 07, 2008 3:35 PM
To: 

Subject: RE: [cgal-discuss]To understand half edge data structure

Hi Mathieu,

It is not working with the same error.

I tried again as follows,

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

For more understanding, I amd using CGAL::Polyhedron_3 with Polyhedron_3.h.
Is there anything else should be included?

Samuel

-----Original Message-----
From: 

[mailto:]
 
Sent: Wednesday, May 07, 2008 3:26 PM
To: 

Subject: Re: [cgal-discuss]To understand half edge data structure

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
>> >  >
>> >  >
>> >  >  --
>> >  >  You are currently subscribed to cgal-discuss.
>> >  >  To unsubscribe or access the archives, go to
>> >  >  https://lists-sop.inria.fr/wws/info/cgal-discuss
>> >  >
>> >  --
>> >  You are currently subscribed to cgal-discuss.
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>> >
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>> >
>>

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