[aspect-devel] natural strain / geoid / ParaView questions

Rene Gassmoeller rene.gassmoeller at mailbox.org
Tue Nov 14 09:49:19 PST 2017

Hi Ludovic,

About 1: Currently only the deformation gradient tensor F (in the
language of the manual) is tracked and output by ASPECT. Everything else
in that figure I created in VisIt (which has the nice option to compute
eigenvectors of tensors). I am sure this is somehow possible in Paraview
as well (probably using the python programmable filter?), but for this
application Visit seemed easier (let me know if you want more advice on
how to do it). On the other hand it might make sense to create a
postprocessor for ASPECT that does the same thing internally, if you are
interested we can talk about how to implement such a postprocessor.

2. Shangxin Liu would be the best contact for the geoid as he imlemented
the methodology. He would know if it is already published, or which
references are appropriate. The dynamic topography methodology has a
reference in the manual section, I am not sure if there are publications
by Jacky, Ian, or Shangxin (the authors of that section) that describe
it in more detail than the general reference.

3. Timo already said it, but unfortunately the support for cartographic
projections in Paraview is not really existent. If you calculate
spherical coordinates (e.g. with Timo's script, or by setting up
calculators that do that), you can create a programmable filter with my
following script to generate a (crude) Mollweide projection for a global
model (not sure that is what you want?):

theta =inputs[0].PointData['Latitude']/1.01

phi =inputs[0].PointData['Longitude']

bigt =theta

fori inrange(100):

bigt =bigt -(2*bigt +sin(2*bigt) -3.1415*sin(theta))/(2+2*cos(2*bigt))

x =2*sqrt(2)*phi*cos(bigt)/3.1415

y =sqrt(2)*sin(bigt)

output.PointData.append(x, "x")

output.PointData.append(y, "y")

output.PointData.append(bigt, "bigt")

An alternative approach can be to preprocess your data in Paraview, write it into text files ("Save Data"), 
and then use GMT to create a map. Cumbersome. Again, a map projection of output data would 
be a nice to have feature, let us know if you are interested in adding something.


On 11/13/2017 10:41 AM, Jeanniot, L. (Ludovic) wrote:
> Hi!
> I am Ludovic Jeanniot and I do a postdoc with Cedric Thieulot.
> I am currently learning ASPECT and there are several points where I
> need some enlightenments, please:
> *1. "Tracking finite strain":  *
> I got confused with Figure 31b. Does the natural strain distribution
> should be a postprocess output of ASPECT or is it later derived from
> the strain in ParaView?
> Also it would be great to get to know how to add the eigenvectors.
> *
> 2. "Postprocessing spherical 3D convection":*
> Is there any references about the methodology and calculation of the
> geoid anomalies (and possibly with it the dynamic topography)?
> *3. Cartographic projections:*
> How is it possible to represent the different cartographic projections
> in ParaView? Does the unofficial Evenden (2008) library work or is it
> too old or maybe someone else has another solution?
> Thanks!
> Ludovic
> _______________________________________________
> Aspect-devel mailing list
> Aspect-devel at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel

Rene Gassmoeller

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