Create Spline-Patch-Group

[jzwar]

In order to describe complex geometries, more than one spline-patch is required. Currently they are stored as a simple list of splines. However, for analysis, more information might be required, such as:

• Connectivity information
• Boundary information
• (optional) material IDs

Having such a class, would facilitate the multipatch output for several IGA-solvers. It could further provide a few functions

• show for multipatch, storing already sampled geometries
• multithread sample-ing
• select_boundary for interactively chosing boundaries based on patch and face IDs

We should also make sure, that intermediate "designs" can be stored in json format, so boundaries can be stored and altered later!

This is related to gismo, mfem and nutils exports and might be of interest to the users of these softwares.

[jzwar]

Please leave a comment for discussion, as to what is required and what might be missing

[j042]

now #62 is merged those things should be easier to extend. select_boundary should be in gustaf

[j042]

#77

[jzwar]

#94