Results at any location

dolfinx
1

Hello everybody,

I try to get the results at a location within a domain where no nodes exist. Or simply meaning, I’m looking for a function like:

location = [xl,yl,zl]
result_at_location = interpolate(R,location)

Here, R is a function representing the result field. If an MWE is needed or helpful, I could construct them. But I hope that somewhat ‘generic’ question is as distinctive as I think.

Best,
Mario

2

You can use R.eval as shown in: Implementation — FEniCSx tutorial

3

Looks promising! Is this functionality coupled with a specific version of dolfinx?

4

No, dolfinx.den.Function.eval has been in DOLFINx since prior to the v0.1.0 release

5

Ah, I see. Could it be that

colliding_cells = geometry.compute_colliding_cells(domain, cell_candidates, points.T)

given in your tutorial, was introduced in a recent version of dolfinx? I found no entry in the changelog. And, is:

colliding_cells.links(i)

restricted to meshes created via gmshio? Loading of xdmf-meshes leads to the error that ‘links’ doesn’t exist.

Thanks for your help!

6

In version 0.3.0 this function was called dolfinx.geometry.select_colliding_cells, see: https://github.com/jorgensd/dolfinx-tutorial/blob/v0.3.0/chapter1/membrane_code.ipynb
This was changed in the 0.4.0 release:
https://github.com/jorgensd/dolfinx-tutorial/blob/v0.4.0/chapter1/membrane_code.ipynb

As you are using an older version of DOLFINx, you need to follow the tutorial for the relevant version (i’ve posted the equivalent code for 0.3.0 and 0.4.0 above

7

Great, I got it! Thanks a lot @dokken