[Paraview] Caching within a class, avoiding vtkGeometryFilter

[David E DeMarle]

Hi Mark,

There has been some recent discussion of this on the vtk-developers
mailing list.
See http://www.vtk.org/pipermail/vtk-developers/2008-July/005393.html
Unfortunately there is no resolution yet.

cheers,
Dave DeMarle

On Fri, Aug 1, 2008 at 9:34 AM, Olesen, Mark
<Mark.Olesen at emcontechnologies.com> wrote:
> I've now had a bit of time to picking up on my old problem:
> [http://www.paraview.org/pipermail/paraview/2008-May/007917.html]
>
> Even after I have some caching within the reader (thus sparing most
> I/O), I see that a large amount of time is actually being spent in
> vtkGeometryFilter.
>
> If we assume, for simplicity, that the geometry represented by the
> reader is invariant over time but the field values can change, how can
> this be coded to have the pipeline not update the geometry, but just
> update the field values?  Since the geometry doesn't change, the speed
> of examining such transient data should only be marginally slower than
> changing between various fields at a single time step.
>
> To make it a bit easier, I'm ignoring the field values and within the
> RequestData() method I have something like this:
>
>
> vtkMultiBlockDataSet* output = vtkMultiBlockDataSet::SafeDownCast
> (
>    outputVector
>        ->GetInformationObject(0)
>        ->Get(vtkMultiBlockDataSet::DATA_OBJECT())
> );
>
> ... do something with UPDATE_TIME_STEPS() and set
>    bool needsUpdate = true/false;
>
>
> // first time
> if (!output0_)
> {
>    output0_ = vtkMultiBlockDataSet::New();
>    needsUpdate = true;
> }
>
> if (needsUpdate)
> {
>    UpdateReaderGeometry(output);
>    output0_->ShallowCopy(output);
>    cout<< "full UPDATE ---------\n";
> }
> else
> {
>    output->ShallowCopy(output0_);
>    cout<< "cached UPDATE ---------\n";
> }
>
> I actually don't know if this is a reasonable approach, but it doesn't
> segfault and paraview still displays the geometry at each time step.
> Nonetheless, the modification time of 'output' still causes the
> GeometryFilter to execute and the field values are not yet copied.
>
> Rebuilding the field values from scratch is fast enough that I may not
> need to cache them, but how can I get the output not to re-trigger the
> GeometryFilter?
>
> Thanks,
>
> /mark
> This e-mail message and any attachments may contain
> legally privileged, confidential or proprietary Information,
> or information otherwise protected by law of EMCON
> Technologies, its affiliates, or third parties. This notice
> serves as marking of its "Confidential" status as defined
> in any confidentiality agreements concerning the sender
> and recipient. If you are not the intended recipient(s),
> or the employee or agent responsible for delivery of this
> message to the intended recipient(s), you are hereby
> notified that any dissemination, distribution or copying
> of this e-mail message is strictly prohibited.
> If you have received this message in error, please
> immediately notify the sender and delete this e-mail
> message from your computer.
>
> _______________________________________________
> ParaView mailing list
> ParaView at paraview.org
> http://www.paraview.org/mailman/listinfo/paraview
>