How to create a .sur file in CalculiX?


I’m new to preCICE and CalculiX, so maybe this is a daft question:

How do I create the .sur file? I understand the concept and that the .sur file contains volume elements (linear or quadratic tets) sorted by which of the elements 4 surfaces is lying in the surface.

But how do I create this surface? I use Salome for meshing, and CGX to create the msh and nam files. But “send interface abq sur” creates an empty file. I have tried a mesh with additional 2D surface elements, but CalculiX doesn’t like those (so I have to delete them in the all.msh) and also tried to create a group of volume elements that lie in the surface (>= 3 nodes in Ninterface), but that doesn’t seem to work, either.

I guess I’m missing something fairly basic here.

@TSchenkel welcome! For such a CalculiX-specific question, I guess you will have better chances asking in the CalculiX forum.

I see that this is a duplicate of How do I create the .sur file for nearest-projection?, so I lock this thread to keep everything in one place. :smile: