The model describes the local behavior of local parts of the perceived surface and local illumination. More complex 3-D surfaces would each behave exactly the same way locally, i.e. every local part of a curved surface would respond to locally perceived illumination, resulting in a global pattern of shading as seen on a curved surface, and similarly for a trihedral corner, or any other complex shape represented by the system. Similarly, a model of soap bubble formation that accurately models the emergence of the perfect spherical bubble, would automatically also model the complex unstable wobbly bubble shapes observed while a bubble is being inflated, or the complex intermediate surfaces observed when many different bubbles adhere to each other. The general idea is that since this system creates a geometrically representative spatial replica of both perceived surfaces and the propagation of light through space, any complex surface present in the system would automatically exhibit correspondingly complex patterns of light and shadow, but calculated by the same local geometrical computations. Again, there is no need for a discrete "medium illumination" signal, just a general analog illumination variable that ranges continuously from dark through bright, just as perceived illumination is itself observed as an analog quantity.