I had a question related to the one asked earlier about the use of BoundaryInfo. If I understand well, you can use this class to associate id's to faces of elements as a means of representing certain physical entities, composed of a number of mesh entities, on the boundary, that have a similar physical meaning, such as the nodes and elements comprised in an inlet or an outlet in CFD.
Here is my question: How do I define similar objects, but related to three dimensional areas that are to be grouped based on their physical behavior, rather than two dimensional (in the case of a 3D mesh). Examples of this would be the regions composed of different materials in termal or electromagnetic simulations.
Thanks a lot!