[Paraview] Fwd: Question about strain from filter: Compute Derivatives -> Vector -> Strain.... type?

[Andy Bauer]

I believe that is the order. Usually what I do to remember the exact order
is to create an analytical function based on point coordinates with the
calculator filter and then use the gradient filter to check on the order.


On Thu, Mar 27, 2014 at 3:18 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>wrote:

> One last question, Andy -
>
> Can I assume that the cell-based, 9-element array that 'Compute
> Derivatives' (Vector gradient) produces is essentially an array of:
>
> [ derivs[0],  derivs[1],  derivs[2],.... derivs[8] ]
>
> (to use the formatting from your previous email)?
>
> Thanks again,
>
> Tim
>
>
> On Thu, Mar 13, 2014 at 1:22 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>wrote:
>
>> Awesome! Thanks for the help, Andy!
>>
>> Tim
>>
>>
>> On Thu, Mar 13, 2014 at 12:35 PM, Andy Bauer <andy.bauer at kitware.com>wrote:
>>
>>> Hi Tim,
>>>
>>> The class that does that computation is called vtkCellDerivatives. It
>>> looks like the part of that code that does the strain computation is:
>>>           tens->SetComponent(0,0, derivs[0]);
>>>           tens->SetComponent(0,1, 0.5*(derivs[1]+derivs[3]));
>>>           tens->SetComponent(0,2, 0.5*(derivs[2]+derivs[6]));
>>>           tens->SetComponent(1,0, 0.5*(derivs[1]+derivs[3]));
>>>           tens->SetComponent(1,1, derivs[4]);
>>>           tens->SetComponent(1,2, 0.5*(derivs[5]+derivs[7]));
>>>           tens->SetComponent(2,0, 0.5*(derivs[2]+derivs[6]));
>>>           tens->SetComponent(2,1, 0.5*(derivs[5]+derivs[7]));
>>>           tens->SetComponent(2,2, derivs[8]);
>>>
>>> My suggestion would be to use one of the gradient filters (either
>>> Compute Derivatives or Gradient of Unstructured Data Sets) and then either
>>> use the Calculator filter (slower but simpler) or the Python Programmable
>>> filter (faster but more complicated) to compute your desired results.
>>>
>>> Regards,
>>> Andy
>>>
>>>
>>> On Thu, Mar 13, 2014 at 3:23 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>wrote:
>>>
>>>> Fair enough.... I'd like to think that since the infinitesimal strain
>>>> tensor is just a simplified version of the Green-Lagrange tensor (really,
>>>> some usually-small terms just get assumed to be zero), that the Paraview
>>>> designers utilized a fully-designed Green-Lagrange formulation, which will
>>>> approximate to the infinitesimal strain tensor then the strains are small...
>>>>
>>>> But it'd be great to get a definitive answer.. otherwise I ened to
>>>> think about creating my own filter to determine the finite strain tensor.
>>>>
>>>> Thanks for the comment,
>>>>
>>>> Tim
>>>>
>>>
>>>
>>
>>
>> --
>> Tim Bhatnagar
>> PhD Candidate
>> Orthopaedic Injury Biomechanics Group
>> Department of Mechanical Engineering
>> University of British Columbia
>>
>> Rm 5000 - 818 West 10th Ave.
>> Vancouver, BC
>> Canada
>> V5Z 1M9
>>
>> Ph: (604) 675-8845
>> Fax: (604) 675-8820
>> Web: oibg.mech.ubc.ca
>>
>
>
>
> --
> Tim Bhatnagar
> PhD Candidate
> Orthopaedic Injury Biomechanics Group
> Department of Mechanical Engineering
> University of British Columbia
>
> Rm 5000 - 818 West 10th Ave.
> Vancouver, BC
> Canada
> V5Z 1M9
>
> Ph: (604) 675-8845
> Fax: (604) 675-8820
> Web: oibg.mech.ubc.ca
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.paraview.org/pipermail/paraview/attachments/20140330/b0409414/attachment.html>