Depth Perception: Binocular and Monocular Cues

Monocular vs. Binocular: Whether information requires one eye or two.
Pictorial vs. Non-pictorial: Whether information is available in a static image (photograph).
Visual vs. Oculomotor: Information from the retinal image versus signals from eye muscle movements.
Ordinal vs. Metric: Whether a cue indicates object order (which is closer) or provides a specific measure of distance.

Advantages of Frontal Eyes: Allows for binocular summation (lower detection thresholds) and precise depth perception through overlapping visual fields.
Vergence: An oculomotor, metric cue involving the angular position of the eyes. Small angles indicate long distances; large angles indicate short distances.
Stereopsis: The process of extracting depth from the different viewpoints of the two eyes.
Binocular (Retinal) Disparity: The difference in retinal positions for the same object in each eye. Described by Wheatstone (1838).
The Horopter: The line of locations where images fall on corresponding retinal points (zero disparity).
- Crossed Disparity: Objects nearer than the horopter.
- Uncrossed Disparity: Objects further than the horopter.
Fusion and Diplopia: Panum’s fusional area is the zone where single vision occurs. Outside this area, diplopia (double vision) occurs.
Simulating 3D: Accomplished via stereoscopes, anaglyphs (red/cyan), polarization, or shutters to deliver separate images to each eye.
Random Dot Stereograms (RDS): Developed by Julesz (1971) to demonstrate Cyclopean Vision, where shapes emerge only after binocular combination.
Autostereograms: Also known as SIRDS (Tyler, 1979); single images with repeating patterns that use vergence adjustment to create disparity.

Familiar Size: Metric cue where the perceived distance of a known object is judged by the size of its retinal image.
Perspective:
- Linear Perspective: Assumption that parallel lines converge in the distance.
- Detail Perspective (Texture Gradient): Assumption that texture elements are uniform in size.
Motion Parallax: A non-pictorial, metric cue where closer objects move faster across the retina than distant objects as the observer moves.
Height in the Visual Field: Objects higher in the visual field are perceived as more distant, assuming they rest on a ground plane.
Aerial (Atmospheric) Perspective: Distant objects appear lighter, lower in contrast, and more blue due to light scattering by atmospheric particles.
Occlusion (Interposition): An ordinal cue where a foreground object blocks the view of a more distant object.
Shadows:
- Cast Shadow: The separation between an object and its shadow indicates height and depth.
- Attached Shadow: Shading patterns reveal surface orientation (convex vs. concave) assuming a light source from above.
Blur: The depth of field provides metric information; sharp edges typically indicate the object in focus or the nearer object during occlusion.
Accommodation: An oculomotor cue where the ciliary muscles change the lens shape to focus on objects ( $\text{Metric}$ ).

Emmert’s Law: Perceived size of an object is proportional to its perceived distance for a constant retinal image size.
Misapplied Constancy Scaling: Illusions like the Ponzo illusion or the Ames room occur when the visual system calculates size based on inaccurate depth percepts.