image: Binocular disparities are used for stereopsis. (A) Two views of a simple 3-D scene are shown. The eyes are looking at point F1 and a second point P is positioned above, to the right, and closer in depth than F1. Panels show a side view and a view from behind the eyes. (B) Retinal projections of P from the viewing geometry in (A). The yellow and orange dots are the projections in the left and right eyes, respectively. The difference between these projections is binocular disparity. In this example, the image of point P is shifted leftward in the left eye and rightward in the right eye. (C) For a given point in the scene, the binocular disparity can change substantially depending on where the viewer is looking. In the left panel, the same point P is observed, but the viewer is looking at point F2, which is closer than P. In the right panel, the binocular disparities projected by P are shown for both situations [disparities from (B) are semitransparent]. For the viewing geometry in (C), the images of point P are reversed. This material relates to a paper that appeared in the May 29, 2015, issue of Science, published by AAAS. The paper, by W.W. Sprague at University of California, Berkeley in Berkeley, CA, and colleagues was titled, "Stereopsis is adaptive for the natural environment." view more
Credit: [Credit: Sprague, <i>et al</i>. Sci. Adv. 2015;1:e1400254]