dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Aug 20, 2008 at 07:15:06PM +0100, Garth N. Wells wrote:
> 
> 
> Anders Logg wrote:
> > I'm not sure this will work. If you attach 6 vertices to a triangle by
> > 
> >   <triangle index="0" affine="false" v0="0" v1="1" v2="2" v3="4" v4="5" v5="6"/>
> > 
> > then all sorts of things will break (I imagine). A triangle always has
> > three vertices.
> >
> 
> I noticed this too. It would make some things troublesome.
> 
> > The geometry of the triangles is separate.
> > 
> > Maybe we could just add extra data which could be "control points" for
> > the cell facets? For P2 it would be the edge/face midpoints.
> >
> 
> I like the idea of defining facet data which would contain the necessary 
> info.

A problem with defining facet data is that the facet numbering is not
known a priori. It depends on the algorithm used by DOLFIN to compute
the facets from the cells. So we can't store for example a mesh
function over the facets since the facet numbering may change.

When we read input from VMTK, we need to read facet data (boundary
markers) and these are stored relative to the cell to which the facet
belongs and the local number of the facet relative to the cell (which
is unique).

There is an example in data/meshes/aneurysm.xml.gz.

-- 
Anders

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