Recently developed high-density directional displays have the ability to evoke the accommodation responses and provide smooth motion parallax. In the this work, we explain how smooth motion parallax is produced by the high-density directional displays. We also examine the effects of the motion parallax on object depth perception using 64-directional displays. Cylindroids with different ellipticities that have coarse random dot patterns or checker patterns on their surfaces were displayed, and observers were asked to describe the perceived ellipticities. The density of the random dots was so coarse that more than half of the observers could not correctly perceive the ellipticities using only binocular parallax. The use of the motion parallax improved thier ellipticity perception greatly. Moreover, almost all observers could perceive the ellipticities to a certain precision only with the motion parallax. The binocular disparity and motion parallax produced by the high-density directional display were so effective that the use of checker patterns on the cylindroid surfaces results in little improvement.
