Modelling of aspherical nebulae - I. A quick pseudo-3D photoionization code

International audienceWe describe a pseudo-3D photoionization code, NEBU_3D, and its associated visualization tool, VISNEB_3D, which are able to treat a wide variety of nebular geometries easily and rapidly, by combining models obtained with a 1D photoionization code. The only requirement for the code to work is that the ionization source is unique and not extended. It is applicable as long as the diffuse ionizing radiation field is not dominant and strongly inhomogeneous. As examples of the capabilities of these new tools, we consider two very different theoretical cases. One is that of a high-excitation planetary nebula that has an ellipsoidal shape with two polar density knots. The other is that of 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