[vtkusers] Temporal datasets that have changing properties

[David E DeMarle]

John,

I say we change DATA_GEOMETRY_UNMODIFIED to GEOMETRY_STATIC and use
PRESERVES_GEOMETRY for the filter flag. We should also use
TOPOLOGY_STATIC and PRESERVES_TOPOLOGY as the case may be.

See the changes I made a few months ago to
vtkStreamingDemandDrivenPipeline and, as soon as the code freeze is
over, TestPriorityStreaming. The change preserves attribute,
geometric, and or topological information across filters when it is
safe to do so. I think it will be helpful when we implement
intelligent caching.

cheers,
Dave DeMarle

On Thu, Mar 12, 2009 at 12:13 PM, John Biddiscombe <biddisco at cscs.ch> wrote:
> Gerrick
>
> I've been working on some aspects of this (“DATA_GEOMETRY_UNMODIFIED” in
> particular), but it is not used by anyone other than me as far as I know.
> DATA_GEOMETRY_UNMODIFIED would be what you want, except that
> 1) It should be GEOMETRY_STATIC and should be set by the reader. In your
> case it wouldn't be any good because if the data changed after 10 steps,
> then the flag is lying.
> 2) No filters support it other than the ones I've customized for my own
> needs
> 3) I'm working on improved ways of handling this, but you won't see anything
> for months, specifically, there should be a GEOMETRY_STATIC for sources that
> have unchanging geometry (over time), but filters which pass geometry
> through from source to sink unchanged would need a separate key (Like
> GEOMETRY_UNMODIFIED, but with a better name). I haven't settled on a
> stratagy that I'm happy with yet.
>
> So in short, unless you want to get quite deep into vtk internals, "no" you
> can't really do what you want.
>
> I have written data into xdmf and modified the vtk read/writers to allows me
> to re-use meshes over time steps - but it's not yet ready for public
> consumption, when it is stable and useful, I'll let you know.
>
> Perhaps someone else out there has made some progress on this front?
>
> JB
>
>
> Hi All,
> I have a temporal data that changes structure less frequently than the
> properties on the structure. For instance in 100 timesteps the structure may
> only change once every ten timesteps.
> Are there ways to handle this in VTK? Currently I re-create my mesh every
> time step but I think I can make things faster by only changing the
> properties when needed and caching the structure.
> I saw some posts on the developer list about setting the
> “DATA_GEOMETRY_UNMODIFIED” flag but I couldn’t quite follow along. Also,I’m
> still on vtk 5.2.1 rather than cvs head.
>
> Gerrick
>
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> --
> John Biddiscombe,                            email:biddisco @ cscs.ch
> http://www.cscs.ch/
> CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07
> Via Cantonale, 6928 Manno, Switzerland      | Fax:  +41 (91) 610.82.82
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David E DeMarle
Kitware, Inc.
R&D Engineer
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Clifton Park, NY 12065-8662
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