[Paraview] Use separate arrays for colormap and opacity

[Evan Kao]

Hello all,

We would like to be able to visualize an object without tying the colormap
to the same array as the opacity.  Specifically, we would like to animate
pathlines and color them by velocity, while setting their opacity according
to particle age.  Is this possible in Paraview?

Thanks,
Evan Kao
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[Paraview] Filter MaterialInterfaceFilter

[José Luis López López]

Dear colleagues,

I have a set of data:

DATASET STRUCTURED_POINTS

and I want to use the MaterialInterfaceFilter to measure the center of mass
of some isovolume inside my dataset.

According to the ParaView website the filter MaterialInterfaceFilter can
measure the center of mass. However. its input should be:

Input to the filter can be a hierarchical box data set containing image
data or a multi-block of rectilinear grids.

Do you have an idea what can I do? Or do you suggest another idea to
measure the center of mass. I attached an image of my dataset. It is 3D and
the isovolume of the droplet is the desired isovolume to measure.


Thanks a lot,
Jose
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Re: [Paraview] Calculation of Lambda2 using ParaView...

[Andy Bauer]

Hi,

The best way to do this would be in a programmable filter. I'm guessing
numpy has some method to compute eigenvalues for non-symmetric matrices.
Beyond that adding the capability to the Python calculator or some other
filter would be needed.



On Tue, Jun 13, 2017 at 3:35 AM, Stefan Melber  wrote:

> Hi Andy,
>
> i think i found the reason: i need the computation of (unsymmetrical)
> eigenvalues for lambda2 - however it seems that the function "eingenvalue"
> calculates only symmetric ones (see https://www.paraview.org/
> ParaView/Doc/Nightly/www/py-doc/paraview.vtk.numpy_
> interface.algorithms.html). How can i calculate the unsymmetric ones with
> ParaView?
>
> Best regards,
>
>  Stefan
>
>
> Hi,
>
> Maybe compute each portion manually and check that against the correct
> values. Also, verifying the gradient calculation is correct is another
> thing to look at. If the grid isn't specified properly then the gradient
> operation will likely be wrong.
>
> On Fri, Jun 9, 2017 at 8:46 AM, Stefan Melber 
> wrote:
>
>> Hi,
>>
>>
>> for vortex-detection i (tried) to calculate the lambda2-criterion (see
>> e.g. https://en.wikipedia.org/wiki/Lambda2_method) with ParaView. The
>> way of calculation is based on this link http://www.iesensor.com/blog/2
>> 016/01/24/using-paraview-to-visualise-vorticity-lambda2-vort
>> icity-q-criterion/.
>>
>> However - the results are a kind of "wrong" - see attached pictures:
>> l2_solver.png shows what the flow solver writes out for lambda2,
>> l2_paraview.png shows what calculated with the algorithm below.
>>
>> Calculation of lambda2:
>>
>> D = Gradients = [d_ij]
>> S = strain(Vel)
>>
>> S = (D + D^T)/2
>> Omega = (D - D^T)/2
>>
>> lambda = EigenValue_of(S^2 + Omega^2)
>>= EigenValue_of(S^2 + (D - S)^2)
>>= EigenValue_of(S^2 + (Gradients - strain(vel))^2)
>>
>> lambda2 = lambda_Y
>>
>> and in ParaView this mean
>>
>> o Vector of velocity with "Calculator".: Vel =
>> iHat*x_velocity+jHat*y_velocity+kHat*z_velocity
>> o Gradients of Vel with "GradientOfUnstructuredDataSet": switch on
>> "compute gradient" and name it "Gradients"
>> o Calculate lambda with "PythonCalculator".: lambda =
>> eigenvalue(strain(Vel)**2+(Gradients - strain(Vel))**2)
>> o Caluclate lambda2 with Calculator: lambda2 =
>> lambda_Y
>>
>>
>>
>> Does anyone see the error why the calculation of lambda2 with ParaView
>> does not work?
>>
>> Remark: i contacted the author of the blog above already - seems he never
>> tested his calculation and has no idea what is "wrong".
>>
>> Stefan
>>
>>
>>
>> 
>>
>>  _/ *Dr. Stefan Melber-Wilkending*
>>_/_/
>>  _/  _/ Deutsches Zentrum für Luft-
>>  _/_/_/_/_/_/_/_/_/_/ und Raumfahrt e.V. (DLR)
>>_/_/_/_/
>>  _/_/_/_/ German Aerospace Center
>>_/_/_/_/_/_/_/_/_/_/  Institute of Aerodynamics
>>  _/  _/  _  _   and Flow Technology
>>  _/_/   | \ |  |_|   Transport Aircraft Branch
>>  _/ |_/ |_ | \
>>  Lilienthalplatz 7
>>  Fields of activities:  38108 Braunschweig
>>  Germany
>>  o Numerical Windtunnel Simulation
>>  o Aero-Acoustic Windtunnel DesignPhone : +49 531/295-2836
>> <%28531%29%20295-2836>
>>  o Numerical Optimization Fax. .: +49 531/295-2914
>> <%28531%29%20295-2914>
>>  o Visualization Techniques
>>  o High-Lift Aerodynamics   Email : stefan.mel...@dlr.de
>>  o Glider-Aerodynamics  Web ..: http://www.dlr.de/AS
>>
>>
>> 
>>
>>
>> ___
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Please keep messages on-topic and check the ParaView Wiki at:
>> http://paraview.org/Wiki/ParaView
>>
>> Search the list archives at: http://markmail.org/search/?q=ParaView
>>
>> Follow this link to subscribe/unsubscribe:
>> http://public.kitware.com/mailman/listinfo/paraview
>>
>>
>
>
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Re: [Paraview] Calculation of Lambda2 using ParaView...

[Stefan Melber]

Hi Andy,

i think i found the reason: i need the computation of (unsymmetrical) 
eigenvalues for lambda2 - however it seems that the function 
"eingenvalue" calculates only symmetric ones (see 
https://www.paraview.org/ParaView/Doc/Nightly/www/py-doc/paraview.vtk.numpy_interface.algorithms.html). 
How can i calculate the unsymmetric ones with ParaView?


Best regards,

 Stefan



Hi,

Maybe compute each portion manually and check that against the correct 
values. Also, verifying the gradient calculation is correct is another 
thing to look at. If the grid isn't specified properly then the 
gradient operation will likely be wrong.


On Fri, Jun 9, 2017 at 8:46 AM, Stefan Melber > wrote:


Hi,


for vortex-detection i (tried) to calculate the lambda2-criterion
(see e.g. https://en.wikipedia.org/wiki/Lambda2_method
) with ParaView. The
way of calculation is based on this link

http://www.iesensor.com/blog/2016/01/24/using-paraview-to-visualise-vorticity-lambda2-vorticity-q-criterion/

.

However - the results are a kind of "wrong" - see attached
pictures: l2_solver.png shows what the flow solver writes out for
lambda2, l2_paraview.png shows what calculated with the algorithm
below.

Calculation of lambda2:

D = Gradients = [d_ij]
S = strain(Vel)

S = (D + D^T)/2
Omega = (D - D^T)/2

lambda = EigenValue_of(S^2 + Omega^2)
   = EigenValue_of(S^2 + (D - S)^2)
   = EigenValue_of(S^2 + (Gradients - strain(vel))^2)

lambda2 = lambda_Y

and in ParaView this mean

o Vector of velocity with "Calculator".: Vel =
iHat*x_velocity+jHat*y_velocity+kHat*z_velocity
o Gradients of Vel with "GradientOfUnstructuredDataSet": switch on
"compute gradient" and name it "Gradients"
o Calculate lambda with "PythonCalculator".: lambda =
eigenvalue(strain(Vel)**2+(Gradients - strain(Vel))**2)
o Caluclate lambda2 with Calculator: lambda2 =
lambda_Y



Does anyone see the error why the calculation of lambda2 with
ParaView does not work?

Remark: i contacted the author of the blog above already - seems
he never tested his calculation and has no idea what is "wrong".

Stefan





 _/ *Dr. Stefan Melber-Wilkending*
   _/_/
 _/  _/ Deutsches Zentrum für Luft-
 _/_/_/_/_/_/_/_/_/_/ und Raumfahrt e.V. (DLR)
   _/_/_/ _/
 _/_/_/_/ German Aerospace Center
   _/_/_/_/_/_/_/_/_/_/ Institute of Aerodynamics
 _/  _/  _  _   and Flow Technology
 _/_/   | \ |  |_|   Transport Aircraft Branch
 _/ |_/ |_ | \
Lilienthalplatz 7
 Fields of activities:  38108 Braunschweig
Germany
 o Numerical Windtunnel Simulation
 o Aero-Acoustic Windtunnel DesignPhone : +49 531/295-2836

 o Numerical Optimization Fax. .: +49 531/295-2914

 o Visualization Techniques
 o High-Lift Aerodynamics   Email : stefan.mel...@dlr.de

 o Glider-AerodynamicsWeb ..: http://www.dlr.de/AS




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