Motivated by the issue that led to [6b4c8e95] I tested the possibility to work with 3D surfaces in HyTeG. As it turns out this works at least partially. We can construct them, use them to generate function objects, interpolate expressions into the associated FE spaces and output the functions for visualisation correctly.
I added a tiny
3DSurfaceDemo app to show that and adapted the
SPHdemo to allow computing the spherical harmonics only on a thin shell:
What I did not test so far is anything operator related, though.