Making a dielectric function using C++

To make a dielectric function that is compatible with FPS use the following code as an example:

In this example we define a sphere with radius of R, refractive index of "refractive_index" and located at point (i0,j0,k0) in a cubic domain of free space

 

for (int i=0; i<i_max;i++){
    for (int j=0; j<j_max; j++){
        for(int k=0; k<k_max;k++){
           if((pow(i-i0,2.0) + pow(j-j0,2.0) + pow(k-k0,2.0)) <= pow(R,2.0)){
               epsilon[i][j][k] = pow(refractive_index,2.0);
}
}
}
}