[Paraview] using integrate variables between two filters

[Michael Rapson]

Ah, found my problem. I was naming the output from the first
calculators staring with a digit, 01_x for example. This was fine for
displaying etc but does not seem to be valid for the next calculator.
I have fixed this now, please ignore my previous message.

Regards,
Michael

On Thu, Dec 10, 2009 at 3:35 PM, Michael Rapson <rpsmic001 at gmail.com> wrote:
> Dear Sven,
>
> Thank you for that answer. I would have struggled to find that post
> and both do exactly what I need.
>
> Something that I noticed when applying step 4:
>> 4) Use Calculator #2 on AppendAttributes1 to take difference (eg h1-h0).
> If h1 and h0 are extracted as a single component of a vector, eg
> velocity_0, I get an error when applying this calculator:
>
> ERROR: In /home/kitware/ParaView-3.6/ParaView3/VTK/Common/vtkFunctionParser.cxx,
> line 1629
> vtkFunctionParser (0x3376110): Syntax error: operator expected; see position 2
>
> ERROR: In /home/kitware/ParaView-3.6/ParaView3/VTK/Common/vtkFunctionParser.cxx,
> line 1629
> vtkFunctionParser (0x3376110): Syntax error: operator expected; see position 2
>
> Warning: In /home/kitware/ParaView-3.6/ParaView3/VTK/Graphics/vtkArrayCalculator.cxx,
> line 394
> vtkArrayCalculator (0x3036ec0): An error occured when parsing the
> calculator's function.  See previous errors.
>
> I have seen these errors on Linux paraview 3.6.1 and 3.2.1 as well as
> Mac 3.4. Interestingly enough if I set up the initial two calculators
> with a scalar field, e.g. pressure, it works fine and I can later swop
> the pressures to velocity_0 with out any problem. (In order to test
> this I used a single .vtk file with a vector velocity a scalar
> pressure and made a copy of the file copy of the file. Once the inputs
> were swopped I confirmed that the difference between the velocities in
> the files was zero.)
>
> I was surprised that taking the velocities directly failed, but
> specifying the pressures first and swopping seems to be a good work
> around.
>
> Thanks for the help!
> Michael
>
>
>
>
> On Wed, Dec 9, 2009 at 2:15 PM, Sven Buijssen
> <sven.buijssen at tu-dortmund.de> wrote:
>> Hi Michael,
>>
>> Your first question has been discussed before, e.g., here:
>> http://markmail.org/message/jon3wyz3ve2rzza5
>>
>> Regarding your second question you're looking for the ParaView filter Resample
>> with Dataset. It takes two inputs which will be your coarse and refined grid.
>> See the filter's help for more details.
>>
>> Sven
>>
>>
>> ----- Original Message -----
>> From: Michael Rapson <rpsmic001 at gmail.com>
>> To: paraview at paraview.org
>> Sent: 12/09/09 12:41:12
>> Subject: [Paraview] using integrate variables between two filters
>>> Hi all,
>>>
>>> I use Paraview to post process results from finite element simulations
>>> and find it very useful. There is however, one thing that seems
>>> feasible but I cannot find out how to do in Paraview and I would
>>> appreciate it if someone could tell me whether it is possible.
>>>
>>> I write data from my simulation to file as .vtk with a number of
>>> variables at each mesh location (say x velocity, y velocity and
>>> pressure). In Paraview I can load the file, compute result =
>>> velocity_X - velocity_Y using the calculator and then integrate
>>> variables to get the integral of velocity_X - velocity_Y on the mesh.
>>> This is obviously not a very useful result in general, what I really
>>> want is to compute velocity_X_simulation_1 - velocity_X_simulation_2,
>>> where simulation 1 and 2 share the same mesh but some different
>>> parameters. I can use a similar method to the one described above as
>>> long as the data from both simulations is stored in the same .vtk
>>> file, but is it possible to load two .vtk files into a single
>>> pipeline, or to access data across pipelines for the integrate
>>> variables method?
>>>
>>> An even more optimistic question, if the two simulations are run on
>>> meshes that exist on the same domain (i.e. region in space) but have a
>>> different set of nodes, say the mesh for simulation 2 is refined once
>>> more than the mesh from simulation 1, is it possible for Paraview to
>>> interpolate data from the less refined mesh to the more refined mesh
>>> in order to compute velocity_X_simulation_1 - velocity_X_simulation_2
>>> and integrate?
>>>
>>> The first scenario seems technically feasible, if it has been offered
>>> in Paraview. Alternatively, are there specialized programs that can
>>> read two .vtk files and combine their variables into a single .vtk
>>> file? The second is more optimistic and couldn't be done without
>>> explicitly interpolating the results from one mesh to the other. I
>>> have found the Group Datasets filter, but this does not seem to quite
>>> do it (the data sets are marked (partial) once grouped and calculating
>>> differences fails).
>>>
>>> Thank you for any ideas about how I could achieve this, and also
>>> confirming whether it can be done in Paraview or if I should make
>>> another plan will help me to move forward.
>>>
>>> Regards,
>>> Michael
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>>
>