  We present new calculations of the attenuation of stellar light from spiral
galaxies using geometries for stars and dust which can reproduce the entire
spectral energy distribution from the UV to the FIR/submm and can also account
for the surface brightness distribution in both the optical/NIR and FIR/submm.
The calculations are based on the model of Popescu et al. (2000), which
incorporates a dustless stellar bulge, a disk of old stars with associated
diffuse dust, a thin disk of young stars with associated diffuse dust, and a
clumpy dust component associated with star-forming regions in the thin disk.
The attenuations, which incorporate the effects of multiple anisotropic
scattering, are derived separately for each stellar component, and presented in
the form of easily accessible polynomial fits as a function of inclination, for
a grid in optical depth and wavelength. The wavelength range considered is
between 912 AA and 2.2 micron, sampled such that attenuation can be
conveniently calculated both for the standard optical bands and for the bands
covered by GALEX. The attenuation characteristics of the individual stellar
components show marked differences between each other. A general formula is
given for the calculation of composite attenuation, valid for any combination
of the bulge-to-disk ratio and amount of clumpiness. As an example, we show how
the optical depth derived from the variation of attenuation with inclination
depends on the bulge-to-disk ratio. Finally, a recipe is given for a
self-consistent determination of the optical depth from the Halpha/Hbeta line
ratio.
