Seeing

The first form, construction of a virtual space, refers to the process by which a viewer perceives a three-dimensional layout of objects in space when viewing a flat surface presenting the pictorial cues to space, i.e., perspective, shading, occlusion, and texture gradients. This process, which is akin to map interpretation, is the most abstract of the three. It is abstract because the stimuli for many of the physiological reflexes associated with the experience of a real three dimensional environment are either missing or inappropriate for the information on a flat picture which depicts a space differing from the picture surface. Some of the consequences of this inappropriateness are discussed by Sedgwick (Chapter 30), Goldstein (Chapter 31), Cutting (Chapter 32), Ellis et al. (Chapter 34) and by Enright (Chapter 38).