Tracking finite strain


I was trying to plot the finite strain using the “Finite strain tracking” cookbook of the manual. But I can not plot the orientation of the half-axes of the finite strain ellipsoids. Is there any way to find it out?


Hi Poulami,

Thank you for posting to the forum!

My recollection is that @gassmoeller made that plot with Visit, as opposed to Paraview, as Visit had a mechanism for easily calculating and plotting eigenvectors. Perhaps Paraview can do that now as well?

I don’t recall the specifics, so I will let Rene add in further details.

Another alternative would be to load the vtk files into python and then make the relevant calculations/plots through matplotlib, etc.


Sorry for the late reply. Poulami see my separate email. Visit requires you to build a tensor property, before computing the eigenvectors, but I dont exactly recall how we did that (it was some form of filter or expression you needed to generate). Alternatively deal.II 9.3 and recent ASPECT versions can now visualize tensor properties automatically, but I dont know how easy it is to upgrade your model, or how well paraview supports further processing once you have visualized the strain tensor.


In Visit, this is how to create a tensor-valued variable:

  • In the “Controls” menu at the top, select “Expressions”
  • Click “New” at the bottom left and give it a name at the top right
  • Below the name, select that you either want a tensor or a symmetric tensor
  • In the text box below it, you then need to provide a list of the variables that were written into the output file in a format so that Visit recognizes that these are going to be the components of the tensor you are defining. I forgot the exact format, but with a bit of play and/or google, you will be able to find how it wants this to be specified.

The new expression then defines a variable that you can then use in the “Add > Tensor” plot.


hello all,

Thanks for getting back to me!
I have made tensors using the integrated strain components obtained from ASPECT. When I tried to calculate the eigenvector of the this tensor VisIt is showing this error

ERROR: Vector: ()

viewer: The ‘eigenvector_AVT_mag’ expression failed because Can only take magnitude of vectors.

Any idea why is this happening?



I have no idea. You will have to consult the Visit manual to see what can and cannot be done with vectors and tensors, and what the proper syntax is.


Dear all,

Finally it worked in VisIt. Thanks a lot!