CGAL users discussion list

[Mariette Yvinec <>]

Hi

In fact, cgal 3.8, allows to have a fine control on the sizing field.
I quote the doc below :

template<class SizingField>

        
        
        
        
     Mesh_cell_criteria_3<Tr> mcc ( FT radius_edge_bound,  SizingField radius_bound);
        
        
    Returns an object to serve as default criteria for facets. The type SizingField must
be a model of the concept MeshDomainField_3. The behavior and semantic of the arguments are the same 
as above, except that the radius bound parameter is a functional instead of a constant.

Thus, the parameter SizingField is just required to be a model
of MeshDomainField_3, that is some scalar function on the domain.
In particular it is quite possible to set such a function using a separate
voxel image as you are planing ....
and the same is true for the SizingField parameter in Mesh_facet_criteria_3.

Hope this helps,
Mariette



Le 02/05/11 01:54, toddoe a écrit :

HI All,
hope this isn't too silly of a request, but I would really like to control
the mesh sizing using a separate voxel image, rather than an analytical
function.

The reason for this is because i've written a bunch of nice mesh sizing
tools in Matlab that use gradient limiting and other mesh or problem
specific features that i need. The way I do it now is to generate a
supporting 'image' of the voxel object where each sizing voxel contains the
local target mesh size (i do this all in Matlab, which i can 'understand'...
i've written my own crude tet mesher but want to use CGAL).

I have compiled cgal 3.8 and have 3d meshing working quite well (win7,
64bit). Now if I could just locally control the mesh size that would be
amazing.

I've read the docs and the discussions here and understand that I can set
mesh sizes for different domains, but I really want to control mesh size
within the domain, and i can't use an analytical function because the mesh
size depends upon a non-analytical distribution (viz. the original voxel
image intensity, actually bone density, just for one example). Another
application is aneurysm, which is a really difficult meshing problem because
the vessel wall gets really thin (need local sizing control, some
preliminary pics attached below).

I hope this explanation makes sense. 
Basically, I want to control the local mesh size within a domain with a
separate voxel image.

Any help or ideas are greatly appreciated. I'm only a beginner at C++
(really good at matlab and python) but I understand most basic concepts. At
least enough that I've been able to modify the examples and add input-output
and basic gui functionality.

Thanksinadvance,
todd

p.s. 3-domain mesh of a brain aneurysm... latest fiddling around. the vessel
wall is 'transparent' but right now too thick because of lack of local
sizing control.
about 200k elements.
http://cgal-discuss.949826.n4.nabble.com/file/n3489004/brainan1.jpg 
http://cgal-discuss.949826.n4.nabble.com/file/n3489004/brainan2.jpg 
http://cgal-discuss.949826.n4.nabble.com/file/n3489004/brainan3.jpg --
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-- 
Mariette Yvinec
Geometrica project team
INRIA  Sophia-Antipolis