Defining electrical properties for different regions from gmsh

Hello colleagues

I have imported a 3D mesh from gmsh with different physical volumes inside it in freefem, all are imported in one mesh.
I need to define different epsilon on each region. I can get my physical volumes tages by command

fespace Ph(Th, P1); Ph reg = region; plot(reg); real[int] tags; Unique(reg[], tags); cout << "tags"<<tags << endl;

May you suggest me a command so to define epsilons for each region based on physical volumes tags?

Thanks in advance.

You’ve probably already figured it out, but if you’re still looking for an answer (untested code):

fespace V0(Th, P0);

// region tags
int air1 = 3;
int porcelain1 = 4;
int air2 = 5;

real eps0 = 8.8541878128e-12;
real epsr_air = 1.00059;
real epsr_porcelain = 4;

V0 eps = eps0 * ( epsr_air *(region == air1 || region == air2) +
                epsr_porcelain * (region == porcelain1) );

Thanks alot for your response,

So eps considers separate permittivity of each region?