  We developed a 3D pure LTE radiative transfer code to derive observables
expected for RSGs, with emphasis on small scale structures, from
radiative-hydrodynamic (RHD) simulations of red supergiant stars (RSGs) carried
out with CO5BOLD (Freytag et al. 2002). We show that the convection-related
surface structures are observable with today's interferometers. Moreover, the
RHD simulations are a great improvement over parametric models for the
interpretation of interferometric observations.
