dolfin team mailing list archive

[Kent Andre <kent-and@xxxxxxxxx>]

On ti., 2009-06-23 at 11:09 -0600, Bartosz Sawicki wrote:
> Kent Andre wrote:
> > On ma., 2009-06-22 at 20:57 +0200, Anders Logg wrote:
> >> On Mon, Jun 22, 2009 at 12:46:09PM -0600, Bartosz Sawicki wrote:
> >>> Kent Andre wrote:
> >>>> On ma., 2009-06-22 at 00:40 -0600, Bartosz Sawicki wrote:
> >>>>> On 22/06/09 12:06 AM, Anders Logg wrote:
> >>>>>> On Sun, Jun 21, 2009 at 11:36:29PM -0600, Bartosz Sawicki wrote:
> >>>>>>> On 19/06/09 02:53 PM, kent-and@xxxxxxxxx wrote:
> >>>>>>>> When using VMTK the boundary indicators are stored as a set of arrays
> >>>>>>>> with names
> >>>>>>>> boundary facet cells,
> >>>>>>>> boundary facet numbers
> >>>>>>>> boundary indicators
> >>>>>>>> The two first arrays are used to find the global facet numbers.
> >>>>>>>> The function computes a mesh function based on these arrays.
> >>>>>>>>
> >>>>>>>> This was what Anders prefered since VMTK does not now anything
> >>>>>>>> about the global numbering of facets in Dolfin (without linking it into
> >>>>>>>> Dolfin).
> >>>>>>>>
> >>>>>>>> This is not a VMTK specific problem, but I do think VMTK is the only
> >>>>>>>> mesh-generator
> >>>>>>>> that let you store boundary indicators at the moment. I guess we should add
> >>>>>>>> this to NetGen as well, both Hans Petter Langtangen and Douglas Arnold has
> >>>>>>>> bugged
> >>>>>>>> me about this the last few days.
> >>>>>>> I'm every day user of this functionality. I use Netgen generated models, 
> >>>>>>> but also other software which add boundary indicators to existing 
> >>>>>>> meshes. Netgen supports boundary indicators quite well, both by geo 
> >>>>>>> files, and by GUI. I don't understand what you want to add?
> >>>>>> Is it possible to set DOLFIN boundary indicators from Netgen? I didn't
> >>>>>> know.
> >>>>> It is definitely possible :) I don't have direct converter from Netgen 
> >>>>> vol to Dolfin xml. Most of my old models were stored in Diffpack grid 
> >>>>> format, so I'm using grid to xml converter.
> >>>>> Netgen can export to the grid format, so this is not a big issue.
> >>>> It is not possible to store the boundary indicators in Dolfin format
> >>>> using Netgen, at  the current time. I wrote the Netgen -> dolfin filter
> >>>> in Netgen so I should know :).  
> >>>>
> >>>> But it should be possible to include support for that in a similar
> >>>> fashion as we did in VMTK. 
> >>> You are right that Netgen doesn't support Dolfin XML mesh format. But it 
> >>> doesn't mean that is not possible to use boundary indicators generated 
> >>> by Netgen in Dolfin. Converterting via Diffpack grid file preserves 
> >>> boundaries.
> >>>
> >>> The algoritm is simple:
> >>> 1. Generate mesh using Netgen.
> >>> 2. Mark boundaries indicators.
> >>> 3. Export to Diffpack format.
> >>> 4. Convert Diffpack to XML.
> >>> 5. Enjoy boundary indicators in Dolfin.
> >>>
> >>> cheers,
> >> Nice, but not optimal. At some point, we need an application that can
> >> do all of these (and more). There seem to be a couple of different
> >> options:
> >>
> >>   1. Extend Netgen with full support for DOLFIN (and change the toolkit...) 
> >>   2. Extend Gmsh with full support for DOLFIN (and change the toolkit...)
> >>   3. Extend MeshBuilder to do mesh generation (using for example Netgen)
> >>   4. ?
> >>
> >> Any thoughts on these options?
> >>
> >> The problem with (3) is that no one is really developing MeshBuilder,
> >> except when we pay Kalkulo (http://simula.no/applications/kalkulo/) to
> >> do it.
> >>
> > 
> > It should be fairly easy to include bc indicators in NetGen. I can look
> > at it, I think I need to update the filter anyway to make sure the mesh
> > is ordered correctly according to UFC. 
> 
> Are you going to extend Netgen to enable export into dolfin-xml?
> You mentioned about some filter, is it somewhere in dolfin repository? I 
> can't find anything. Can upload your code into dolfin-convert utility?

Netgen, in its newest version, can export to dolfin xml. But only the
mesh, not the bc indicators. 

> 
> > In general it is rather easy to write out the mesh and indicators
> > compared to actually making it. I bet we can make Gmsh write Dolfin mesh
> > in just a few hours (but I have not looked at Gmsh). 
> 
> I'm sure that it will be easy. But don't you thing that good converter 
> is more flexible solution?
> 
> cheers,
> 

I don't know. 

Kent