dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

On 16 March 2012 12:49, Johan Hake <hake.dev@xxxxxxxxx> wrote:
> On 03/16/2012 10:28 AM, Garth N. Wells wrote:
>>
>> On 16 March 2012 09:17, Johan Hake<hake.dev@xxxxxxxxx>  wrote:
>>>
>>> Hello!
>>>
>>> I have implemented a new version of UnitSphere based on subdivision of an
>>> initial octahedral surface mesh and tetrahedralization using the CGAL
>>> framework.
>>>
>>> This is all fine, but CGAL uses alot of time tetrahedralizing the initial
>>> surface mesh. CGAL is also doing some funny things with the surface mesh.
>>>
>>>  1) It subdivide the initial surface mesh, which I want to prevent. Is
>>>     that possible.
>>>  2) 1) results in small triangles on the surface, but large triangles
>>>     in the interior. I set a tentative volume constraint based on the
>>>     size of a triangle of the input mesh.
>>>
>>> You can try it out here:
>>>
>>>  bzr branch lp:~dolfin-core/dolfin/hake-trunk
>>>
>>>  from dolfin import *
>>>  mesh = UnitSphereNew(4)
>>>  # Do not try larger subdivisions than 4, at least for now.
>>>
>>
>> Did you look at the CGAL demo for generating a mesh or a sphere:
>>
>>
>>  http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Mesh_3/Chapter_main.html#Subsection_50.3.1
>>
>> ? It uses an implicit surface description. I has planning to add
>> support for meshing geometries from implicit descriptions.
>
>
> No I didn't. Are we using the implicit interface in dolfin?
>

Not yet, but I will add an interface for it,

> Using a subdivision algorithm is probably the fastest and cleanest way to
> generate the surface of a Sphere. Using an implicit function might create
> surfaces which does not follow the input mesh, which is what I want.
>

What you you mean? The mesh will conform to the true surface to within
a specified tolerance. What the implicit representation has trouble is
with sharp edges.

Garth

> johan
>
>
>> Garth
>>
>>>
>>> Johan
>>>
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>
>