Augmented and Virtual Reality Systems - pág.39

If motionless, the cube could appear as any of the random silhouettes shown in Figure 3.21. Even the square shape in the upper left would be recognized as just that-a square. But rotated through the remaining views, most observers would quickly recognize the source of the silhouettes as a cube, even in the absence of other depth information or surface details.

Figure 3.21 The kinetic depth effect demonstrates the ability to perceive 3D structure from moving 2D views and silhouettes.

This phenomenon first appeared in scientific literature in the 1950s based on experiments performed by research scientists Hans Wallach and D. N. O´Connell (Wallach and O´Connell, 1953). Widely studied since, there are two key theories as to how the 3D forms are perceived. The first is the result of changes in the pattern of stimulation on the retina as the object moves, and the second is related to previous experience. In most situations, the kinetic depth effect is experienced along with other depth cues, such as that of motion parallax described earlier.

Familiar Size

As the name of this cue indicates, if we know how large an object is at a distant location, our brain can use that understanding to estimate absolute distances, such as shown in Figure 3.22. Some studies speculate that this cue can be recharacterized as the awareness of the relationship between the size of one´s body and the size of an object as knowing the size of an object must be anchored to some relative metric, and the body is really the only relevant thing we have to which sizes can be compared (Linkenauger et al., 2013).

Figure 3.