CGAL users discussion list

["Santosh Tiwari" <>]

http://www.cgal.org/Manual/3.2/doc_html/cgal_manual/Alpha_shapes_3/Chapter_main.html

The methods I mentioned take point cloud as the input.

Alpha shape also takes point cloud as the input.

> Hi, Santosh Tiwari
>
> Could you explain a little about the "alpha complex of the shape and
> output
> all the surface facets"? Do you mean that those works you mentioned are
> for
> the implicit function, like Laurent Rineau said in the other message?
>
>
>
>> If you want mesh re-construction from point cloud. You have following
>> options.
>>
>> 1. If you want to use CGAL, you may create an alpha complex of the shape
>> and output all the surface facets. This method works but is not very
>> reliable and may not always give you the mesh you want.
>>
>> 2. If you know the approximate direction of normals at every vertex, use
>> something like poisson surface reconstruction. It is a powerful and
>> reliable method.
>>
>> 3. If you do not have the normals, you can use the program provided at
>> the
>> following link.
>> http://www.den.rcast.u-tokyo.ac.jp/~yu-ohtake/software/index.html
>> This method also is not very reliable. It works on most standard models
>> but for complex data sets, it does not do a good job.
>>
>>
>>
>>
>>
>>
>>> On Monday 09 June 2008 18:07:18 Hui Ding wrote:
>>>> Hi all,
>>>>
>>>> I have this file of 3D points whose data are from an image depth,
>>>> which
>>>> means those 3D points define an object 3D non-closed. I want to mesh
>>>> this
>>>> object, is it possible that i can use the make_surface_mesh to do
>>>> that?
>>>> and
>>>> how? for example, how to define the sphere_3, the centre, etc? Can
>>>> anybody
>>>> give an idea? Thanx!!
>>>
>>> Here is an answer I made in another thread of this list, last year ("3D
>>> surface meshing", 2007/06/08):
>>>
>>> « You seem to have a set of points, as input. Surface_mesher in
>>> CGAL-3.3
>>> is a
>>> package to mesh a implicit function. What you need is a surface
>>> reconstruction algorithm (from a set of points). You cannot use
>>> Surface_mesher.
>>>
>>> However, there exists some algorithm to compute an implicit function,
>>> from
>>> a
>>> set of points, whose zero level represents a smooth surface interpoling
>>> the
>>> points. If you have such a function, then you can use the
>>> Surface_mesher
>>> package. »
>>>
>>> As far as I know, there are not any code in current CGAL-3.3.1 for such
>>> a
>>> task.
>>>
>>> --
>>> Laurent Rineau
>>> INRIA - Sophia Antipolis
>>> BP 93, 2004 Route des Lucioles
>>> 06902 Sophia Antipolis Cedex FRANCE
>>> Tel: +33 4 92 38 78 62 (Fax: +33.4.97.15.53.95)
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>>>
>>
>>
>> --
>> Santosh Tiwari
>> Fluor Daniel EIB 326
>> Clemson University, Clemson, SC 29634
>> http://www.clemson.edu/~stiwari/
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-- 
Santosh Tiwari
Fluor Daniel EIB 326
Clemson University, Clemson, SC 29634
http://www.clemson.edu/~stiwari/