Example of the Ca_m and Hα_m emission covered by the simulation (Test #1) for a given (x₀, y₀) pair (x₀ = 5, y₀ = -5). The colour code corresponds to increasing average ff (from 0.001, yellow, to 0.6, blue). Only a fraction of the points are shown for practical reasons (the original grid is 10 times denser). Superposed straight lines indicate the position of constant Ca_pl values (from 1.1 in yellow to 15.6 in blue). The observed points for stars in the 3600–3700 K bins are represented in red.