Photon destruction probability as a function of wavelength and geometrical depth in the mean stratification of a metal-poor ( [Fe/H]  =  −3) red giant surface convection simulation. Darker shades indicate lower photon destruction probability. The destruction probabilities are here computed assuming that only continuous processes contribute to scattering extinction. Spectral lines (appearing as white vertical stripes in the upper part of the figure) are treated in pure absorption.