The Neural Control of Vision

L. The Processing of Depth

The processing of depth information represents one of the major computational problems for the nervous system. The main reason for this is that the retina is actually just a two-dimensional surface, so that processing in the third dimension requires some rather ingenious computations. In fact to deal with this problem the nervous system has developed several ways of calculating depth, eight of which are listed in Figure 51. Here four of these mechanisms will be discussed: stereopsis, motion parallax, shading and perspective.