2D cross sections of the Cloudy, Dusty, and Shell geometries. The darkness of the squares schematically indicates the density of dust in that area. For clumpy models, the density ratio is 100 (i.e., clumps have 100 times the density of the diffuse medium), while for homogeneous models, the density ratio is 1 (i.e., the same density for gray and black squares). The stellar population is uniformly distributed inside the smooth circle.