Abstract
The phenomenon of motion transparency is well known and has been extensively investigated for decades. A typical demonstration of motion transparency shows random dots moving in two directions, but the perception of depth is ambiguous. Here we find that when motion parallax is used to present planes of random dots at different depths, then this facilitates the perception of transparency and makes depth less ambiguous. The motion of random dots was synchronized to participants' head movements, to present frontoparallel overlaid surfaces at different depths, within a 28 deg circular mask. The number of overlaid planes, dot density (0.5, 1, 2, 4, 8 dots/deg2) and depth separation between the planes was varied. Four participants indicated how many planes in depth they were able to perceive. In separate trials, participants also indicated the depth of the planes using a depth matching task. A coherence noise task was also used in order to determine the percent signal dots that was necessary to perceive transparency with motion parallax. The results indicated that participants could perceive at most three simultaneous overlaid surfaces. Increasing either the number of planes or dot density had a detrimental effect on the perception of transparency. At higher dot densities, only two planes could be perceived. The results with the coherence noise task indicated that transparency could be perceived at percent signal levels comparable to those for motion without transparency. These results are similar to those found for motion transparency in which disparity was used to present planes at different depths, and suggests that the number of planes that can be perceived may be limited to at most three because of effects of attention. Moreover, depth perception was likely degraded at the highest densities because of inhibitory interactions between adjacent dots moving in opposite directions and depth averaging.
Meeting abstract presented at VSS 2017