Dynamic Occlusion and Optical Flow From Corrugated Surfaces

Dynamic occlusion (i.e., accretion and deletion of optical texture at the occluding edge) can occur under many different environmental conditions, for example, objects hidden behind other objects when viewed by a moving observer, objects moving in front of other objects, or an observer approaching a brink. Because each of these conditions may require the actor to respond differently, the actor may need to be able to differentiate these situations reliably. This study was directed at the optical pattern induced by dynamic occlusion that occurs when one locomotes over a rolling terrain (i.e., a corrugated surface). Two experiments were conducted for this purpose. Participants viewed displays simulating their translation along a corrugated surface in which surface corrugation, texture type, and texture density varied as part of experimental control. Results demonstrated that the visual system reliably extracts the global flow pattern for accurate perception of heading direction despite the presence of optical disturbances in optical flow. However, performance nearly failed in the unstructured texture displays wherein optical disturbances were less salient. Still, the results provide strong evidence that human observers are sufficiently sensitive to dynamic occlusion to extract information about heading direction.