[Paraview] Questions regarding: volume calculation, xyplot along a curve and tensor calculation

[Renato Elias]

It seems rounding errors... try to scale your model at least 100x to see
what happens...

Just to reforce Jie Xu's problem. It's not the first time the Integrate
Variable presents issues in volume calculations. Take a look:
http://markmail.org/message/67dkxpypfodylfnr#query:volume%20integration%20paraview%20renato+page:1+mid:67dkxpypfodylfnr+state:results

In my case, I don't remember if the problem was solved....

I tried to find my dataset to test it again but I haven't found (yet)....
:-(

Renato.



On Fri, Apr 10, 2009 at 4:30 PM, Jie Xu <victoryxj at gmail.com> wrote:

> Hi Berk,
>
> Thanks for looking at my questions.
>
> 1) I attached a sample data set: test.vtk, and the screenshot of my
> paraview window, from which you can see that the clip is created at
> (0,0,0) with radius of 50e-6, and the calculated volume is
> 3.32862e-13, which is much less than what it should be.
> (Interestingly, in this specific case, the calculated volume is about
> 2/pi times the real volume.)
>
> 2) Thanks for letting me know.
>
> 3) Unfortunately, I have no experience with Python. Now I am trying to
> see if I can use matlab to do the tensor calculates and modify the vtk
> file readable by paraview.
>
> Regards,
> Jie
>
> On Thu, Apr 9, 2009 at 1:51 PM, Berk Geveci <berk.geveci at kitware.com>
> wrote:
> > Hi Jie,
> >
> >> 1) Volume calculation:
> >> I found that the "integrate variables" over a sphere clip never gives
> >> the correct volume. For example, I tried to use a very simple geometry
> >> and a very fine mesh (a 200x200x200 micron cube with 2 micron cube
> >> elements), and use paraview to generate a sphere clip that has radius
> >> of 50 micron in the center of that cube, then I apply the "integrate
> >> variables" filter to the clip and show the "Cell Data", it gives a
> >> volume of 4.78818e-13 instead of 5.236e-13, which is 4/3*pi*r^3. The
> >> discrepancy is so large that it just cannot be due to the coarseness
> >> of the mesh. Different mesh and different size of clips gives
> >> different discrepancies, and I cannot find any obvious relationship
> >> between the paraview-calculated volume and the real volume.
> >
> > When I create a 100^3 wavelet and clip it with a sphere of radius 20,
> > I am getting a volume of 33447.5 which is pretty close to the analytic
> > value of 33510.3. Can you send me a dataset that demonstrates this
> > problem?
> >
> >> 2) X-Y plot: how can I do a xyplot of a scalar along a curved line?
> >> For example, if I have the pressure field data from a
> >> flow-around-a-cylinder case, I want to plot the pressure along the
> >> surface of the cylinder as a function of angle or arc length.
> >
> > You can't, yet. I am working on that feature for the next release.
> >
> >> 3) tensor calculation: I have the pressure field and velocity field
> >> calculated from a CFD tool (Transat in my case), how do I calculate
> >> stress tensors at each point from P V field in paraview?
> >
> > Let me ask a question back : do you have any Python knowledge? We are
> > working on making this really simple but currently the array
> > calculator is too limited and cannot produce tensors. However, this is
> > doable using the programmable filter.
> >
> > -berk
> >
>
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