Top: specific intensities for direction n= (1, 0, 1) in the x–z-plane, for a zero-opacity model. Overplotted is the spatial grid with a typical size of N_x = N_y = N_z = 133 grid points. The thick lines indicate the theoretical boundary of the beam. Middle: projected intensity profile through the area indicated by a straight line in the top panel, covering all rays with direction n and impact parameter p = ±2R_∗, and theoretical intensity profile denoted by dotted lines. The central distance from the origin is 3R_∗. Bottom: specific intensity along n, compared to the theoretical value indicated by the dotted line.