[Paraview] Calculator Filter -- Gradient

[DParker at chromalloy.com]

I have a couple of questions about using the Programmable Filter. I have 
imported Tecplot dataset with the following data: coordsX, coordsY, 
coordsZ, Q1, Q2, Q3, Q4, Q5. 

How would I create a new data array that is Q2^2+Q3^2+Q4^2? 

How would I create a new vector data array (similar to 
Q2*iHat+Q3*jHat+Q4*kHat in the Calculator Filter)?




From:   David E DeMarle <dave.demarle at kitware.com>
To:     DParker at chromalloy.com
Cc:     paraview at paraview.org
Date:   09/10/2010 01:24 PM
Subject:        Re: [Paraview] Calculator Filter -- Gradient
Sent by:        paraview-bounces at paraview.org



On Fri, Sep 10, 2010 at 1:10 PM,  <DParker at chromalloy.com> wrote:
> I have two somewhat related questions:
>
> 1. Is it possible to calculate a gradient vector using the calculator
> filter?

No. The calculator filter does only element wise (cell by cell or
point by point) computations. To compute the gradient you need
information from neighboring elements.

>
> 2. Is it possible to define a new data array using a Python script 
without
> the calculator filter? Currently, I am using several Calculator Filters 
to
> calculate CFD flow variables from the conservative variables. I use a 
Python
> script to create the Calculator Filters, but I'm wondering if I can 
avoid
> the Calculator Filter and directly generate new data arrays for 
plotting.
>

Not with a python script (under the python shell) since that runs on
the client and can't really manipulate the data (which lives on the
server) directly. However, the python programmable filter runs on the
server, and with that you can create new arrays, and access
neighboring elements as well.
See http://www.paraview.org/Wiki/Python_Programmable_Filter for examples.

> David Parker
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