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

[Tim Bhatnagar]

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
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