Notes

Monocular Depth Cues:

• Size
• Lighting and Shadows: the image to the right shows six dots whose coloring is just rotated by 180 degrees, we perceive the left set as being a concave and the second set as being convex because we are biased to imagine the source of light as coming from above.
• Interposition
• Clarity and Elevation
• Perspective

Binocular Depth Cues:

• Convergence: if we are observing point A and we want to observe point B, we will have to perform a convergent movement of the eyes. Such movement allows the brain to understand that point B is closer to us that point A. Potentially, via the convergence angle we could estimate the absolute distance of an objects. However, our brain has not evolved to do that.
• Stereopsis (Binocular Disparity): the fact that the two images that we have in the two retinas are not exactly the same allows the brain to estimate the depth of objects in the scene. Referring to the image, if we fix a point, that would be represented in the foveal point of the retina. However, farther points would be represented to the left of the fovea in the right eye and opposite for the other eye. These represent non-corresponding points on the two eyes, which are exploited by the brain to estimate depth. Contrarily to the possibility of evaluating the absolute distance of an object thanks to the convergence of eyes, binocular disparity allows the evaluation of relative distance of an object from the fixation point.