Top row: visibility curves from the RHD simulation with [Fe/H ]  = −3.0 and log g = 1.6 in the optical (left column) and infrared (right column) filters. The visibilities are computed for 36 different azimuth angles 5° apart (thin gray lines). The dotted line is an uniform disk scaled to match the same radius, i.e. the first null in visibility curve. The visibilities are displayed only longward of the first null visibility point (see text). A logarithm scale is used on y-axis. Bottom row: visibility fluctuations with respect to the average value as a function of spatial frequencies.