Eye-accommodation-muscle feedback to vision depth-calculation processes can calculate distances up to two meters. Using metric depth cues can calculate all distances. Observing objects requires at least two eye fixations, which allow vision processing to calculate two different perceived angles, for two different eye, head, and body positions. Vision and body angle-comparison computations can calculate line, surface, feature, and object distances {angle-comparison computations, distances} {distances, angle-comparison computations}.
two sight-line to surface angles
At first eye fixation on a line or surface point, vision calculates a sight-line to point angle. At second eye fixation on a collinear or co-surface point, vision calculates a different sight-line to point angle, because eye, head, and/or body have rotated. At nearest possible line or surface point, sight-line to point angle is 90 degrees. At farthest possible line or surface point, sight-line to point angle is 0 degrees. Angle decreases linearly with distance. If angle of sight-line to line or surface is more perpendicular, line or surface point is nearer. If angle of sight-line to line or surface is less perpendicular, line or surface point is farther.
Comparing sight-line angles to two collinear or co-surface points can calculate distance. Angle difference varies directly with distance. Larger angle change means object is nearer. Smaller angle change means object is farther.
two visual angles
At first eye fixation on an object edge or contour, object has a retinal visual angle, calculating object relative size. At second eye fixation on a different object edge or contour, object has a different retinal visual angle, because eye, head, and/or body have rotated. If sight-line to object edge or contour angle is 90 degrees, visual angle is maximum. At other angles, visual angle is less. Visual angle decreases linearly with distance. If sight-line to object edge or contour is more perpendicular, visual angle is more. If sight-line to object edge or contour is less perpendicular, visual angle is less.
Comparing first and second visual angles can calculate object distance. Angle difference varies directly with distance. Larger angle change means object is nearer. Smaller angle change means object is farther.
two sight-line to point angles
At first eye fixation on an object point, sight-line to point has an angle. At second eye fixation on the same object point, sight-line to point has a different angle, because eye, head, and/or body have rotated. At nearest possible object point, sight-line to point angle is 90 degrees. At other object points, sight-line to point angle is less. Angle decreases linearly with distance. If sight-line to object point is more perpendicular, object is nearer. If sight-line to object point is less perpendicular, object is farther.
Comparing first and second angles can calculate object distance. Angle difference varies directly with distance. Larger angle change means object is nearer. Smaller angle change means object is farther.
two concave or convex corner angles
The first eye fixation on a concave or convex corner determines its angle. The second eye fixation determines a different angle, because eye, head, and/or body have rotated. Smaller-angle concave corners are farther, and larger-angle concave corners are nearer. Smaller-angle convex corners are nearer, and larger-angle convex corners are farther.
Comparing first and second corner angles can calculate distance. Angle difference varies directly with distance. Larger angle change means object is nearer. Smaller angle change means object is farther. Angles and vertices use the same reasoning as corners.
body angle comparisons
First eye fixation and second eye fixation have two different eye, head, and/or body positions. The kinesthetic system determines their angle sets and sends kinesthetic angle-difference information to association cortex for comparison with the corresponding vision angle-difference information.
integration
Comparing the two sets of angle differences calculates absolute metric distances. Accumulating distance information allows building three-dimensional-space information.
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Date Modified: 2022.0224