[Paraview] Comparing datasets - taking a difference

[Moreland, Kenneth]

Although it is possible (and fairly straightforward) to create filters in ParaView that load in all of the timesteps at one time, it is something that we avoid for memory considerations and hence do not have anything exposed that will do so.  However, there are many mechanisms in ParaView that will iterate over all of the timesteps of the input so that your filter sequence will perform its calculations on a per timestep basis (assuming your reader is supporting time).

So for starters, you could simply use ParaView's VCR controls to play through the sequence of time and look at the results.  You can also save an animation to get a sequence of images.  If polygonal data is satisfactory, you can also use the "Save Geometry" option to save the polygonal data over time.

It is technically possible for any writer to iterate over time and save out multiple time steps to the file.  Unfortunately, I don't think any writers yet support this feature.  That's something we need to work on.

-Ken

> -----Original Message-----
> From: paraview-bounces at paraview.org [mailto:paraview-bounces at paraview.org]
> On Behalf Of Christof König Beatty
> Sent: Wednesday, May 07, 2008 8:27 AM
> To: paraview at paraview.org
> Subject: Re: [Paraview] Comparing datasets - taking a difference
>
> I have a follow up question to one I asked a while ago.
>
> While I manage to take differences between two sets, my method (outlined
> below) only allows me to do this for one time step at the time.
>
> Is there a way to take a difference for all times at the same time so
> that I can look at those differences over time, save it etc.?
>
> Thanks!
>
> Chris
>
>
> Christof König Beatty wrote:
> > Thanks a lot for the tip, I wouldn't have figured that out. I had to
> > tweak a little, so here what works for me:
> >
> > 1) Use Calculator #0 to rename the variable from dataset #0
> >    (eg pick just 'h' with result array name 'h0')
> > 2) Use Calculator #1 to rename the variable from dataset #1
> >    (eg 'h' to 'h1')
> > 3) Use "Append Attributes" while having selected both Calculator #0
> >    and #1 to combine the output from 1) and 2). AppendAttributes1
> >    now contains 'h0', 'h1' as well as 'h' (which one?).
> > 4) Use Calculator #2 on AppendAttributes1 to take difference (eg h1-h0).
> >
> >
> > Without introducing step 2) 'h' was still the one from dataset #0 but
> > that might be a Mac version variation. Like this it should always work.
> >
> > Thanks a lot,
> >
> > Chris
> >
> >
> [snip]
> >
>
> --
> Christof Konig Beatty
> Universite catholique de Louvain, ASTR
> 2, Chemin du Cyclotron, bureau 502
> 1348 Louvain-la-Neuve,   Belgium
> Tel: +32 (0)10 47 30 67
> http://www.astr.ucl.ac.be/index.php?page=konig
> --
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