  We describe a pseudo-3D photoionization code, NEBU_3D and its associated
visualization tool, VIS_NEB3D, which are able to easily and rapidly treat a
wide variety of nebular geometries, by combining models obtained with a 1D
photoionization code. We also present a tool, VELNEB_3D, which can be applied
to the results of 1D or 3D photoionization codes to generate emission line
profiles, position-velocity maps and 3D maps in any emission line by assuming
an arbitrary velocity field. As examples of the capabilities of these new
tools, we consider three very different theoretical cases. The first one is a
blister HII region, for which we have also constructed a spherical model (the
spherical impostor) which has exactly the same Hbeta surface brightness
distribution as the blister model and the same ionizing star. The second
example shows how complex line profiles can be obtained even with a simple
expansion law if the nebula is bipolar and the slit slightly off-center. The
third example shows different ways to produce line profiles that could be
attributed to a turbulent velocity field while there is no turbulence in the
model.

Astrophysics