  We present a tool, VELNEB_3D, which can be applied to the results of 3D
photoionization codes to generate emission line profiles, position-velocity
maps and 3D maps in any emission line by assuming an arbitrary velocity field.
  We give a few examples, based on our pseudo-3D photoionization code NEBU_3D
(Morisset, Stasinska and Pena, 2005) which show the potentiality and usefulness
of our tool. One 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. Another 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. A third example shows how, in certain circumstances, it is
possible to discriminate between two very different geometrical structures --
here a face-on blister and its ``spherical impostor'' -- when using appropriate
high resolution spectra. Finally, we show how our tool is able to generate 3D
maps, similar to the ones that can be obtained by observing extended nebulae
with integral field units.
