The objective of the proposed research is the isolation of the various visual cues, known collectively as motion parallax, which mediate veridical perception of the in-depth orientation of a visible object. A simple and representative case is the motion parallax provided by an object whose orientation is itself changing, i.e., an objecti rotating in depth. The applicant has previously identified several cues to rotation direction provided by transformations in the dimension of the retinal projection perpendicular to the axis of rotation. The proposed research continues this analysis and extends it to the dimension of the retinal projection parallel to the axis of rotation. Of the two algorithms for generating simulated retinal projections (orthoginal and polar) only the polar algorithm yields transformation incorporation information regarding rotation direction. One may generate a composite projection, say upon a CRT, using the polar algorithm for one dimension of the projection and the orthoginal (or parallel) algorithm for the other. Such polar-parallel projections are as unnatural, and similarly as valuable, as the early physicist's vacuum. They permit an analytic investigation of motion parallax, one dimension at a time.