Visualization of quadrature functions

[najlkin]

This PR adds support for visualization of quadratures (QuadratureFunction). They can be loaded from a file through the new command line argument -q or in a socket stream with the keyword quadrature (instead of solution). Two options of visualization are offered (which can be switched by Q key):

• Piece-wise constant function on a refined mesh (closed Gauss-Legendre refinement)
• Discontinuous elements with DOFs collocated with the quadrature on the original mesh
• L2 projection onto discontinuous elements

Note that high-order quadratures are supported only for tensor finite elements with the first two options.

TODO 📑 :

• a key for switching
• maintain consistency of quadrature / grid function
• testing
  • 1D
  • vector
  • stream
  • animation
  • scripts
  • parallel
• proper refinement (ClosedGL?)
• check for tensor basis
• README, CHANGELOG

[tzanio]

Looks like f25e99e fixed the CI

[tzanio]

Here is the above picture with the mesh drawn as @vladotomov suggested

[tzanio]

I like the latest changes @najlkin, re-approving 👍

[najlkin]

Wait for 3D 😮 😎

[justinlaughlin]

Looks very cool! Just curious, is there a way to toggle back and forth between quadrature function / grid function or is it one or the other? I naively tried doing both but it didn't like that.

./glvis -np 8 -m ../mfem-parallel/examples/mesh -g ../mfem-parallel/examples/sol -q ../mfem-parallel/examples/sol_qf

I see a lot of nice refactoring work here too like with the enum :).

[najlkin]

Nice to hear @justinlaughlin , you need to choose what you want to visualize - a grid function or quadrature function. If you have a bit of time, please test different options, like dimensions, vector/scalar, shadings, ...

[najlkin]

Ok, I think I am done 🙌 . There is 3D scalar/vector visualization of original quadrature mesh lines, including element-wise cutting plane (cplane=2) 😉 Flat cutting plane (cplane=1) would be difficult and I will leave it for some other day.

[justinlaughlin]

Nice to hear @justinlaughlin , you need to choose what you want to visualize - a grid function or quadrature function. If you have a bit of time, please test different options, like dimensions, vector/scalar, shadings, ...

Forgot to mention I tried some things using ex1: different meshes, mesh refinement, function space order, serial/parallel, shadings, stream/command line; I saw no issues. I can test it out more but it would be next week. Looks good to me!

[justinlaughlin]

oh, forgot to mention I tested on WSL2 ubuntu 20.04

[tzanio]

Very cool, thanks @najlkin!!