ABSTRACT
Abstract-Properties of 3D perception from line drawings are discussed. From them, with dimension counting, it is shown that there exist 3D objects, any depiction of which would be interpreted by the visual system incorrectly. Two examples of such undepictable objects are proposed. Analysis of the examples indicated that 3D interpretation of the line drawings is driven by a tendency to make the interpretation as symmetrical as possible. The algorithmic basis for symmetry search and making use of the additional images provided by symmetry is discussed: it follows from the result that the correspondence between the object points imposed by any symmetry necessarily obeys the rigidity constraint. A model framework for view combination within the same image and between different images in the visual system is proposed; it provides a consistent explanation of a number of 3D perceptual phenomena. This model, in particular, suggests a way to unify such 3D information sources as mesh plots, shading and texture within a single mechanism.
