  We show that the inclination to the line of sight of bipolar nebulae strongly
affects some of their observed properties. We model these objects as having a
spherically symmetric Planetary Nebula and a dusty equatorial density
enhancement that produces extinction that varies with the viewing angle. Our
sample of 29 nebulae taken from the literature shows a clear correlation
between the inclination angle and the near-IR and optical photometric
properties as well as the apparent luminosity of the objects. As the
inclination angle increases --the viewing angle is closer to the equatorial
plane-- the objects become redder, their average apparent luminosity decreases,
and their average projected expansion velocity becomes smaller.
  We compute two-dimensional models of stars embedded in dusty disks of various
shapes and compositions and show that the observed data can be reproduced by
disk-star combinations with reasonable parameters. To compare with the
observational data, we generate sets of model data by randomly varying the star
and disk parameters within a physically meaningful range.
  We conclude that a only a smooth pole to equator density gradient agrees with
the observed phenomena and that thin, equatorially concentrated disks can be
discarded.
