Illustration of one ideal filament and its ideal orientation function. Left: map of an ideal filament (filament with the exact same shape as the model bar) centered on pixel i and oriented at angle (ψ_f)i (here (ψ_f)i < 0). Middle: corresponding binary map, with the model bar overplotted in green. Right: ideal orientation function, from the second step of FilDReaMS applied to the binary map.