How to define mesh connectivity information when using nearest-projection?

Hi everyone, I’d like to ask a very basic question:How to define mesh connectivity information when using nearest-projection?
I’m doing a 3D fluid-solid coupling simulation where the fluid and the solid have an interface for force and displacement data exchange.
I just recently noticed that with nearest-projection need to define the mesh connectivity information.Is it required to provide surface geometry information?Do I need to define surface element or node set in solid? Is there any command in precice-config.xml or solid main file where the surface geometry set definition needs to be written out?I’m still very confused.I’m sorry to ask such a stupid question, but I’m confused. :joy:
Here’s the interface coupling as it is now, it doesn’t look like there are any quad or triangle elements defined:

Is the current mapping method actually nearest-neighbor?
This is the precice-config.xml file
precice-config.xml (2.6 KB)
This is my solid major file:
main.inp (626 Bytes)

Can you please tell me how I can define mesh connectivity information for nearest-projection?
Thank you very much! :smiling_face:

Sorry I was confused before, but now I probably understand how to do it. :joy:
For the fluid-solid coupling problem I’m doing, I should add surface information to the solid,as described on this page:
Configure the CalculiX adapter | preCICE - The Coupling Library
But my element type is C3D8 and I wish to do surface coupling in 3D, can you tell me if this is feasible?
This is my solid mesh:


@mattfrei added support for Hexahedral elements at some point. It doesn’t look like it has made its way into the documentation yet though.

The pull request seems to contain some examples that may help you though.