The linestyles in the plot of Fig.
B signify different ways of computing the line source function, .
In LTE this is given by the Planck function. The 1.5D non-LTE method is the same as the 3D method, except that the horizontal distance between grid points is considered to be infinite. This effectively transforms the inhomogeneous 3D snapshots to an ensemble of 1D model atmospheres. The symbols indicate how the formal radiative transfer was solved once was fixed. It is obvious that the 3D non-LTE effects on are small in the regions where the line is formed.