Abstract
Most ionized nebulae have complex morphological structures. This is true not only for HII regions, but also for Planetary Nebulae. So far, almost all selfconsistent physical analyses of ionized nebulae have used 1D photoionization codes á la Cloudy. A few 3D photoionization codes now exist (Gruenwald et al. 1996; Ercolano et al. 2003). There are practical difficulties with 3D model fitting of real nebulae: one is the enormous parameter space to consider and another one is the fact that 3D codes are very CPU-time and memory consuming: several hours are needed on clusters or supercomputers to make a full model.
