[Gmsh] background mesh

[Martin Genet]

Hello.

I am using the 'background mesh' way to generate a 3D mesh, wich is
great. My problem is the size of the background mesh file, wich is
getting bigger and bigger, which is a problem. Is there a way to solve
this problem, for example by supplying an analytical function in gmsh or
an external function written in python or C++ that return the requested
value of the density of the mesh as a function of the position of the node?

Thank you for your help.
Martin.