Contribution of motion parallax to segmentation and depth perception

Abstract

Relative image motion resulting from active movement of the observer could potentially serve as a powerful perceptual cue, both for segmentation of object boundaries and for depth perception. To examine the perceptual role of motion parallax from shearing motion, we measured human performance in three psychophysical tasks: segmentation, depth ordering, and depth magnitude estimation. Stimuli consisted of random dot textures that were synchronized to head movement with sine- or square-wave modulation patterns. Segmentation was assessed with a 2AFC orientation judgment of a motion-defined boundary. In the depth-ordering task, observers reported which modulation half-cycle appeared in front of the other. Perceived depth magnitude was matched to that of a 3D rendered image with multiple static cues. The results indicate that head movement might not be important for segmentation, even though it is crucial for obtaining depth from motion parallax--thus, concomitant depth perception does not appear to facilitate segmentation. Our findings suggest that segmentation works best for abrupt, sharply defined motion boundaries, whereas smooth gradients are more powerful for obtaining depth from motion parallax. Thus, motion parallax may contribute in a different manner to segmentation and to depth perception and suggests that their underlying mechanisms might be distinct.

Dynamic perspective cues enhance depth perception from motion parallax

“…We only briefly summarize the hardware and software setup because they have been described in detail in previous papers (Yoonessi & Baker, 2011. The observer made lateral head movements, and texture motion on the monitor was synchronized to these movements in order to simulate a real threedimensional surface in depth.…”

“…We use the ratio between head movement and image motion, which we call ''syncing gain,'' as an important parameter in our experiments (Longuet-Higgins & Prazdny, 1980;Ono & Ujike, 2005;Yoonessi & Baker, 2011). The syncing gain is linearly proportional to the rendered depth, and therefore, our graphs of depth ordering performance versus syncing gain are doublelabeled for relative depth.…”

“…Second, most previous motion parallax studies used simulated surfaces whose texture motions are synchronized to observer movement in a simple proportional manner, i.e., orthographic rendering (e.g., Bradshaw, Hibbard, Parton, Rose, & Langley, 2006;Nawrot & Joyce, 2006;Ono & Ujike, 2005;Rogers & Rogers, 1992;Yoonessi & Baker, 2011). These stimuli are ideal for examining the relative motion cue in isolation.…”

Integration of Static and Self-motion-Based Depth Cues for Efficient Reaching and Locomotor Actions

“…Parallax The effectiveness of motion parallax lies in the sensorimotor relationship between the observer movement and consequent retinal image motion, which is dependent on observer movement, scene layout, and point of fixation [7]. Extracting the depth information from the parallax is straightforward once the displacement of the camera ∆p and the displacement of the object in the image ∆x are known using equation (3):…”

Capturing Upper Body Motion in Conversation

“…Our main contributions therefore are: (1) our method provides a high degree of appearance and scale invariance while using only an uncalibrated RGB camera. To this end, we obtain a depth estimate through image motion, given the relationship between both [32]. The scale and spatial context problem is tackled with a single human body detector [9] [7], thus avoiding the clutter of using many part detectors.…”