[Gmsh] 3D mesh between/inside extruded cubes

[Geordie McBain]

2012/5/16 Szalontai Levente <elkszl at uni-miskolc.hu>:
> Dear GMSH Users,
>
> I'm a beginner of using GMSH. The following problem I have: I make a big
> cube and a little cube inside of the big cube, both of them made by using
> extrusion command.
> (see the attached file) When I want to generate the 3D mesh, then it isn't
> meshing the volume among the big and little cube, but only the volume inside
> the little cube. What do I wrong?

The extrusions generate two simply connected volumes, neither of which
you want, so you should Delete them; e.g.

    Delete{Volume{1,2}}

Then create a new volume, being the cubical annulus, e.g.

   Surface Loop(132) = {118, 109, 122, 126, 130, 131};
   Surface Loop(133) = {9, 18, 22, 26, 30, 31};
   Volume(134) = {132, 133}