With the increase in computer power in the last few years, 3D 
hydrodynamical calculations are becoming increasingly common in 
astrophysics. Most hydrodynamical calculations treat radiation in a 
simplified manner, since a full solution of the 3-D non-LTE radiative 
transfer problem is numerically much more expensive than the 
hydrodynamical calculation itself, which already stretch the limits of 
modern parallel computers. In many instances, such as the 
thermonuclear explosion of a white dwarf (thought to be the progenitor 
of Type Ia supernova), the goal of the hydrodynamical simulations is 
to understand the mode of combustion and to handle the effects of 
turbulence in as realistic manner as possible and radiative transfer 
effects are ignored. However, in general since the ultimate validation 
or falsification of the results of sophisticated hydrodynamical 
modeling will be via comparison with the observed radiation from the 
astrophysical object being studied, and the radiation strongly affects 
the physical state of the matter in the atmosphere of the object 
(where the observed radiation originates) the effect of detailed 
radiative transfer effects cannot be ignored.