So the question is: how do the layers fill the space between some hexagonal tiling of circles of some given radius of the first generation of circles. The two parameters of a torus R and μ (see figure 4b,c) can vary simultaneously but for the sake of clarity, let us first consider the variation of only one of them; the second being fixed. We recall that R denotes the radius of the directing circle and that each value of μ corresponds to one particular smectic layer.