  Some features of the physics of radiation-dominated shock waves are discussed
with emphasis on the peculiarities which are important for correct numerical
modeling of shock breakouts in supernova. With account of those peculiarities,
a number of models for different supernova types is constructed based on
multigroup radiation transfer coupled to hydrodynamics. We describe the
implementation of a new algorithm RADA, designed for modeling photon transfer
at extremely-relativistic motions of matter, into our older code STELLA. The
results of numerical simulations of light curves, and continuum spectra are
presented. The influence of effects of photon scattering on electrons, of
thermalization depth and of special relativity in transfer equation is
considered. Some cases are demonstrated, when the appearance of hard X-ray
emission is possible at the shock breakout. The necessary refinements in
numerical algorithms for radiative transfer and hydrodynamics are pointed out.
Prospects for using the results of numerical simulation to analyze and
interpret available and future data from space observatories are discussed.
