[vtk-developers] New nonlinear celltypes

[Will Schroeder]

Soeren -

Very nice, thanks for the contribution. I am going to discuss this 
with a couple of folks here and at Sandia Nat'l Lab who have been 
working on higher-order cells. I do have an initial reaction and I'd 
like to explain what I'm thinking.

If you look at GenericFiltering in VTK5.0 (and I believe that you 
have because you have created a tessellation bridge, that's very 
impressive!) there is an elaborate adaptor mechanism for higher-order 
cells (see the paper http://www.vtk.org/pdf/AdaptorFramework.pdf 
which was presented at IEEE Visualization this year). One of the 
ideas behind this is that no new cells would be introduced into VTK, 
rather an adaptor to an external "library" of elements would be 
created. Part of the rational was to avoid adding lots of new cells 
to VTK, because the potential list is endless and requires modifying 
filters, reader, writers, file formats, etc. for each new cell. So 
another way to do this is to encapsulate your elements into a library 
and then create the bridge (which I think you have done anyway). Then 
the existing generic filtering mechanism could handle the new cells. 
This would minimize changes to VTK.

On the other hand it looks like you've done some great work, and the 
way you've done it provides lots of efficiencies and flexibility that 
the generic filtering mechanism cannot provide. And the elements seem 
to be of the useful sort.

So I guess the question is: are you willing to do everything 
necessary to fully support these new cells: modifying readers, 
writers, filters file formats (including XML), adding tests, etc.? 
This is a lot of work to do and the maintenance issue is the thing 
that is scaring me here.

Will


At 06:50 AM 12/14/2005, Soeren Gebbert wrote:
>Dear developers,
>i have developed new nonlinear celltypes. The company im working in and i
>have decided to contribute this code to VTK. Im working with the VTK 5.0
>branch
>at Linux 32Bit Suse 8.0, 9.2 and windows XP.
>
>I have attached an overview of the new celltypes.
>One file shows the description of the implementation status for each new
>celltype and the status of changes
>in the VTK Filtering and Graphics classes. The other file shows figures
>(like in the VTK books) of the
>new celltypes with numbering and the names in vtkCellType.h.
>
>Because i have integrated these new cells into VTK 5.0, there are some
>changes in other VTK classes i want to provide too.
>I have written a small interacive testprogramm, to test the abilities of
>the new celltypes, like contouring, clipping,  tessellation  (with
>modiefied bridge dataset), picking and so on. We are working with these
>cells for a while, and it seems they are working very well.
>But i was not able to test every functionality of the cells (take a look
>at the implementation status).
>
>If you are interested, please tell me to who i can send the following files:
>1. Sources of the new celltypes
>2. The small interactive testprogramm with modified Bridge dataset (for
>tessellation)
>3. The diffs of all VTK classes i had to modify
>4. The documentation, with:
>    - figures of the cells (openoffice format)
>    - implementation status (openoffice format)
>    - Gnuplot files with shape functions (for 2D cells only ;) )
>    - VTK Dataset for each new cell
>
>I tried to fulfil the the contribution rules (copyright and stuff) and
>the coding standart of VTK.
>
>If you have any question or suggestions, feel free to contact me.
>
>Best regards
>Soeren Gebbert
>
>
>
>
>
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