[vtkusers] Looping Visualization Networks

[Randall Hand]

VTK5 relies very heavily on "pipelines", and everything is "pulled" from the
end of the pipeline.. so if it loops, it gets stuck in an infinite loop
trying to follow the pipeline back to it's source.

What you may have to do is call "GetOutput()" on the final element of your
pipeline, and then perform a DeepCopy to get another dataset, and then you
can delete your pipeline.  Then that copied dataset can be the input to your
next pipeline.

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Randall Hand
Visualization Scientist
ERDC MSRC-ITL

On Mon, Jun 30, 2008 at 12:46 PM, Ryan Barr <ryan_barr_eac at hotmail.com>
wrote:

>  I am deforming a sphereSource using a vtkTransformPolyDataFilter and a
> vtkThinPlateSplineTransform (thanks to Marius Erdt, Karthik Krishnan &
> Miguel Rodriguez). This works fine the first time, but subsequent
> deformations are applied to the original sphere and not the previous
> deformed sphere. In other words, regardless of what is displayed on screen,
> the deformations are being applied to a perfect sphere.
>
> While at the moment I am handling a simple sphere of 50 points, in the
> future I plan on applying this to far more complex models, so I need a
> solution that will work with far more points.
>
> In my search for a solution I read the example in the VTK : An Object
> Orientated Approach to 3D Graphics book on page 115. In this example, after
> the first pass through the filter, the sphereSource is disconnected and a
> filter loop is created. However, for figure 4-22, on page 115, it states
> that looping visualization networks are no longer allowed as of VTK 5.0.
>
> When I try implementing a looping visualization network, similar to the
> example, I get an unhandled exception in vtkAlgorithm::ComputePipelineMTime
>
> My questions are,
> why are looping visualization networks no longer allowed?
> what are we supposed to do instead?
> and are there other (better) ways of maintaining a modified model? Perhaps
> I have to use ITK classes (i.e. DeformableModelSimplexMesh example in ITK's
> InsightApplications)?
>
> thank you
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