From: The World In Your Head by Steven Lehar

Fig. 6.3 A view of the front face of different objects generates an amodal percept of their hidden rear faces. This percept is like a spatial field, in that if a subject were given full three-dimensional models of these objects built as hollow facades with the rear faces missing, the subjects could easily indicate with their hand the perceived spatial extent of those hidden rear surfaces, like a three-dimensional probability field whose shape is determined by the perceived shape of the visible front faces. Alternatively, a subject viewing a stimulus like the house drawing in (E) could be asked to estimate whether the tip of the pointer is inside or outside the volume of the house.