Chapter 2 Principles of Stereoscopic Depth Perception and ...

2.2. Human depth perception
been stimulated by recent developments in computer vision, where shapefrom-X
algorithms (shape from shading, texture, stereo, motion, contour,
etc.) can become more robust when processing cues in combination, and
guidance has been sought in how biological vision accomplishes this feat.
In any parallel cue system cues may act in concert with one another or can
be in conflict. There are a number of ways in which different sources of
information may combine (Howard & Rogers 1995):
Cue averaging: cues are combined based on weighted linear combination.
That is, the independent depth estimates from each cue or
depth module are linearly combined with differential weights assigned
to each cue. This form of interaction has been demonstrated
experimentally on numerous occasions (van der Meer 1979, Bruno
& Cutting 1988, Johnston et al. 1993, Johnston, Cumming & Landy
1994, Frisby, Buckley & Freeman 1996).
Cue dominance: judgements are based on only one cue, where the
other cue is being suppressed when in conflict. An example of such
a situation in the context of stereoscopic displays is the screen edge
effect when a stereoscopic image is presented in front of the screen
plane. The occlusion from the screen border will dominate the depth
percept, and make the image seem to curve backwards at its edges.
Cue dissociation: each cue may be interpreted as arising from a different
object. For example, when the spatial separation of signals to
the auditory and visual system of one object exceeds a certain angle,
two objects may be perceived instead of one, one being visual and
the other auditory. A well-known instance is seeing a jet airplane
fly overhead at a different location from where the sound seems to
originate.
Cue reinterpretation: one of the cues may be interpreted differently
after combination to render it compatible with the other. An example
of such a process is the kinetic depth effect, that is, when the silhouette
of a rotating object, such as a bent piece of wire, appears
three-dimensional even without the disparity cue, yet appears twodimensional
when the motion stops.
Cue disambiguation: this could be regarded as a special case of cue
reinterpretation, where the sign of a cue may be ambiguous (e.g.,
whether the object is in front or behind the fixated object), and
59