It is shown that a convolution with certain reasonable receptive field (RF) profiles yields the exact partial derivatives of the retinal illuminance blurred to a specified degree. Arbitrary concatenations of such RF profiles yield again similar ones of higher order and for a greater degree of blurring. By replacing the illuminance with its third order jet extension we obtain position dependent geometries. It is shown how such a representation can function as the substrate for "point processors" computing geometrical features such as edge curvature. We obtain a clear dichotomy between local and multilocal visual routines. The terms of the truncated Taylor series representing the jets are partial derivatives whose corresponding RF profiles closely mimic the well known units in the primary visual cortex. Hence this description provides a novel means to understand and classify these units. Taking the receptive field outputs as the basic input data one may devise visual routines that compute geometric features on the basis of standard differential geometry exploiting the equivalence with the local jets (partial derivatives with respect to the space coordinates).

We employ an optimal solution to both the "shape from motion problem" and the related problem of the estimation of self-movement on a purely optical basis to deduce practical rules of thumb for the limits of the optic flow information content in the presence of perturbation of the motion parallax field. The results are illustrated and verified by means of a computer simulation. The results allow estimates of the accuracy of depth and egomotion estimates as a function of the accuracy of data sampling and the width of field of view, as well as estimates of the interaction between rotational and translational components of the movement.

The eyes of portrayed people are often noticed to 'follow you' when you move with respect to a flat painting or photograph. We investigated this well-known effect through extensive measurements of pictorial relief and apparent orientation of the picture surface for a number of viewing conditions, including frontal and oblique views. We conclude that cases of both oblique and frontal viewing are very similar in that perception simply follows what is indicated by the proximal stimulus, even though this may imply that the (perceived) physical and pictorial spaces segregate. The effect of foreshortening then causes an apparent narrowing of pictorial objects. We find no evidence for any 'correction' mechanisms that might be specifically active in oblique viewing conditions.