[vtkusers] Making a mesh conformal...

[s comp]

Hi Jonathan,
 
I have not found a vtk tool to make a mesh conformal, but one solution I found was to make the "coarse non-conformal cells" a different cell type. 
 
In my case I hade four cubes neighbouring a larger cube,
 
meaning that this set of faces:
 
o--o--o
|    |   |
o--o--o
|    |   |
o--o--o
 
adjoined this face:
 
o-----o
|        |
|        |
|        |
o-----o
 
initially I was importing all the cubes into vtk as voxels (so a set of eight points). To fix the problem I used a different cell type for the larger cube, VTK_CONVEX_POINT_SET ( the type number is 41) this can be any number of points and vtk will work out the connectivity for you, so order is not important. I included the extra 5 points in the first diagram as well as the eight corner points. Also I had to adjust neighbouring cubes. Another way would be to define new vtk cell types, and this should have the benefit of being faster, as apparently VTK_CONVEX_POINT_SET is not particularly efficient for iso-surface generation etc, and I suspect this might remove the need to modify the neighbouring cubes, (but I am just guessing on this - I am not sure if the mesh needs to be completely conformal for my purposes), but if the fraction of this type of cell is small then the performance drop should be small, I think (I have not tested the perfromance myself yet).
 
I hope this is helpful.
 
If you find any other solutions I would be very interested to know,
and If you decide to create new cell types that I might be able to use I would also be interested - apparently this is quite simple but I'm not very experienced in c++ so am not going to look at doing this just yet.
 
Cheers,
 
Sonam



Jonathan Bailleul <Jonathan.Bailleul at greyc.ismra.fr> wrote:
s comp wrote:
> 
> Are there any tools out there that will take an arbitrary mesh and
> make it conformal?
> 
> (i.e. ensure that the intersection of any two neighbouring cells is
> either a common point, a common edge, or a common face, (no partial
> edges or faces allowed), by dividing cells as necessary, or at least
> make if "facewise conformal")
> 
> I am currently working on modifying the mesh before importing into
> VTK, but figured that maybe someone has already generated a vtk tool
> to do this?
> 
> 
> Thanks,
> 
> Sonam


Dear Sonam,

I would also be very interested into conformal projection for my own
purpose, namely common frame projection for automatic annotation.
Did you find a way to solve your problem?

In advance, thank you very much for any help,


-- 
---------------------------------------
Jonathan BAILLEUL, Doctorant / ATER
GREYC Image - Université de Caen 
http://www.greyc.ensicaen.fr/~bailleul




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