CGAL users discussion list

[Philipp Moeller <>]

王进 
<>
 writes:

> Hi Mr. Moeller,
>
> Thanks for your answers. Regarding the three problems you mentioned, 
> "duplicated vertices" are well understood. However, the other two are 
> not as clear. Could you please define and/or further explain what are 
> "self-intersections and some faces seem to be oriented the wrong way 
> around"? If possible, please also provide some examples.

Self intersecting means that some of the facets in the Polyhedron
intersect each other. Wrong orientation means that not all facets
specify their vertices in the same order (clockwise or
counter-clockwise) throughout the polyhedron.


>
> Greatly appreciate your help.
>
> Wang Jin
>
>
>
>
> At 2012-03-20 20:52:10,"Philipp Moeller" 
> <>
>  wrote:
>>OK, I could reproduce the problem. What sticks out are the duplicated
>>vertices, self-intersections and some faces seem to be oriented the
>>wrong way around. You should try to fix those first, otherwise it is
>>unlikely that mesh simplification will give you the results you want.
>>
>>All of this shouldn't make it crash but it is a good start.
>>
>>
>>HTH,
>>Philipp Moeller
>>GeometryFactory
>>
>>
>>王进 
>><>
>> writes:
>>
>>> Hi,Philipp Moeller
>>> you are right,Simple_cartesian quite faster than Cartesian,but crashed yet
>>> I provide a piece of test data and code in attachment,please tell me the 
>>> problem and give me some suggestions.
>>> thanks very much.
>>> WangJin
>>>
>>> 在 2012-03-18 21:21:02，"Philipp Moeller" 
>>> <>
>>>  写道：
>>>>王进 
>>>><>
>>>> writes:
>>>>
>>>>> Hi,CGAL Developers:
>>>>> I use Lindstrom-Turk edge-collapse algorithm for mesh 
>>>>> simplification,but CGALcrashed at Handle_for.h  
>>>>>
>>>>> bool
>>>>> is_shared() const
>>>>>    {
>>>>>         return ptr_->count > 1;   
>>>>>     }
>>>>>
>>>>> because of ptr_ is invalid pointer.
>>>>> the call stack show as below
>>>>>
>>>>> CGAL::Surface_mesh_simplification::EdgeCollapse
>>>>> ->boost::put
>>>>> ->CGAL::Point_3<CGAL::Cartesian<double> >::operator=
>>>>> ->CGAL::PointC3<CGAL::Cartesian<double> >::operator=
>>>>> ->CGAL::Vector_3<CGAL::Cartesian<double> >::operator=
>>>>> ->CGAL::VectorC3<CGAL::Cartesian<double> >::operator=
>>>>> ->CGAL::Handle_for<boost::array<double,3>,std::allocator<boost::array<double,3>
>>>>>  > >::operator=
>>>>> ->CGAL::Handle_for<boost::array<double,3>,std::allocator<boost::array<double,3>
>>>>>  > >::~Handle_for
>>>>> ->CGAL::Handle_for<boost::array<double,3>,std::allocator<boost::array<double,3>
>>>>>  > >::is_shared() <---crashed
>>>>>
>>>>> for help!
>>>>>
>>>>> Wang 
>>>>
>>>>A hint first: Don't use Cartesian<double>, performance is probably going
>>>>to be a lot better with Simple_cartesian<double>. Simple always means
>>>>better, right? ;)
>>>>
>>>>Can you provide a complete, minimal test-case that shows the problem? I
>>>>have used Mesh simplification extensively throughout last week and
>>>>nothing blew up in my face, but then again I was using Simple_cartesian.
>>>>
>>>>Cheers,
>>>>Philipp Moeller
>>>>GeometryFactory
>>>>
>>
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-- 
Philipp Moeller
GeometryFactory