[Gmsh] Internal surfaces

[Julian Dean]

Dear gmsh,

I'm trying to build a voronoi structure inside a box. I extract my nodes and vertex points from qhull and put them into a script for gmsh and have stumbled across a problem i hope you can help me with. 

As my box contains 8 separate shapes sharing faces I am having an issue defining internal surfaces. As each of my shapes have their own separate vertices and nodes (obviously some are shared) when i write the script some surfaces are unknown. 

It seems that when i create a surface loop with an identified number this can not be changed later but gmsh does not allow an identical surface loop to be formed. 

Is there any way of clearing the surface numbers so that later in the file i can create the same loop or a way of force a re-numbering? Otherwise i have to preform a check of shared surfaces which could be quite tricky. 

Best regards

Julian