[Gmsh] Label Different Regions of Continuous Mesh, Geometry from .stp files

[Justin Clough]

Hello,

I need to create a FE mesh for a geometry made of multiple materials using
Gmsh. The original geometry is from other software packages and is read
into Gmsh via .stp files. Each stp file has one component of the larger
assemble and will need its own material properties.

I'm currently able to read the components into Gmsh and label them with the
`Physical Volume` syntax. The issue is that the surface mesh elements at
the boundaries do not line up with one another; the elements in one
component are not connected to the elements in another.

I made a similar MWE to my problem (files attached). Here I'm trying to
stack two unit cubes in the X direction. The first is made of copper, the
second of tin. My question is: How would I create a single surface mesh at
X=1 which is shared by the two volume meshes instead of two, independent,
surface meshes? Further, how would I do this if the common surface is very
organic in shape?

Thank you in advance for your help! Please let me know if I can provide any
further information.

best,
-Justin Clough
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