Can an internal triangle of a tetrahedron be converted to a bdrelement?

[M8kmyday]

I would like to identify a triangle of a tetrahedron that is internal to the 3D volume of a conformal mesh and convert that triangle to being marked as a bdrelement. I can then apply boundary conditions to that bdrelement using standard bdrelement processing. I reviewed the methods in Mesh, but I do not see a method that can do this. Is it possible to set the identified triangle to be a bdr element [or otherwise add it to the bdrelement list]?

[tzanio]

If the goal is just to apply boundary conditions, it may be simpler to just extract the list of dofs on that face and then add to ess_tdof_list before elimination. The attributes (when present) are just a convenient way to do this but they are not necessary -- the elimination is done based on the list of essential dofs.

cc: @mlstowell

[M8kmyday]

I can certainly do that. However, doing it this way introduces an issue in that I would be using two different processes to accomplish the same goal in setting boundary conditions: using attributes for bdrelements and using a manual ess_tdof_list for faces on elements. I have a lot built around the attributes, including visualization in ParaView for checking boundary assignments. I would prefer to not introduce a second process in the interest of consistency, maintainability, and visualization.

How much harder would it be to use attributes over a manual ess_tdof_list? If it is massively harder, such as requiring derived classes with custom methods, I'll go with the manual ess_tdof_list.

[v-dobrev]

You can try adding the triangle as a boundary element with Mesh::AddBdrTriangle() and then calling FinalizeTopology() and Finalize().

[M8kmyday]

That process seems good. I'll give that a try.