Selective Field Output in G+smo

[jzwar]

Overview

Field output is not in the usual gismo standard and only works together with pygadjoint so I decided to extend the export functionality a little more.

Addressed issues

• Macro spline optimization sometimes only applies to a subset of all macro-spline ctps

@j042 I need this for optimisations only. I can have it on a separate branch for all eternity if you prefer. Also relevant for @kkILSB

Checklists

• [x] Documentations are up-to-date.
• [ ] Added example(s)
• [ ] Added test(s)

[j042]

is it also relevant for @kkCATS?