  Observations and theoretical calculations have shown the importance of
non-spherically symmetric structures in supernovae. Thus, the interpretation of
observed supernova spectra requires the ability to solve the transfer equation
in 3-D moving atmospheres. We present an implementation of the solution of the
radiative transfer equation in 3-D homologously expanding atmospheres in
spherical coordinates. The implementation is exact to all orders in v/c. We use
a new affine method that makes use of the fact that photons travel on straight
lines. We compare our results in 3-D for spherically symmetric test problems
with high velocity fields and find excellent agreement. Our well-tested 1-D
results are based on methods where the momentum directions vary along the
characteristic (co-moving momentum directions). Thus, we are able to verify
both the analytic framework and its numerical implementation. Additionally, we
have been able to test the parallelization over characteristics. Using 512^2
momentum angles we ran the code on 16,384 Opteron processors and achieved
excellent scaling. It is now possible to calculate synthetic spectra from
realistic 3D hydro simulations. This should open an era of progress in hydro
modeling, similar to that that occurred in the 1980s when 1-D models were
confronted with synthetic spectra.
