[vtkusers] vtkArrayCalculator function definition syntax????

[W.T. Bridgman]

On Apr 14, 2006, at 2:08 PM, Randall Hand wrote:

> Unfortunately, VTK's array calculator does not support true cross  
> product computation.  I have a patch in bug 2903 ( http:// 
> www.vtk.org/Bug/bug.php?op=show&bugid=2903&pos=19 ) that adds a  
> "cross(X,Y)" function, but it hasn't been integrated yet.  You can  
> probably grab it & replace your vtkFunctionParser with it and it'll  
> work.

Is it v5.0+ only?  Currently I must build VTK with another module  
that will (currently) not run beyond v4.4.

> In the meantime, you've got 2 options:
>    1) Load your vectors in a 3-scalars, and then perform the cross  
> product yourself as you've shown.
>    2) Use V.ihat, V.jhat, and V.khat to access the 3 components  
> (read: Vector dot i-unit vector, etc)
>
> also, you can't directly write back the results into components..  
> So you'll have to compute each component & multiply by ihat/jhat/ 
> khat and then add the 3 parts together... It's gonna be one massive  
> & messy function line.  And slow to run......

I may examine this as an interim solution.  Hopefully the other code  
will get updated to v5+ soon.

Thanks,
Tom
--
Dr. William T."Tom" Bridgman               Scientific Visualization  
Studio
Global Science & Technology, Inc.          NASA/Goddard Space Flight  
Center
Email: William.T.Bridgman.1 at gsfc.nasa.gov  Code 610.3
Phone: 301-286-1346                        Greenbelt, MD 20771
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