124 CHAPTER 3
b. d.a. c.Figure 3.21 Examples of Pictorial Depth
Cues
(a) Both the lines of the trees and the sides of the road
appear to come together or converge in the distance.
This is an example of linear perspective. (b) Notice how
the larger pebbles in the foreground seem to give way
to smaller and smaller pebbles near the middle of the
picture. Tex t u r e g ra d i e n t causes the viewer to assume
that as the texture of the pebbles gets finer, the pebbles
are getting farther away. (c) In aerial or atmospheric
perspective, the farther away something is the hazier it
appears because of fine particles in the air between the
viewer and the object. Notice that the shed and grassy
area in the foreground are in sharp focus while the
mountain ranges are hazy and indistinct. (d) The depth
cue of relative size appears in this photograph. Notice
that the flowers in the distance appear much smaller
than those in the foreground. Relative size causes
smaller objects to be perceived as farther away from
the viewer.motion parallax
monocular depth perception cue, the
RerceRtion of motion of oDLects in which
close oDLects aRRear to move more
SuicMly than oDLects that are farther away.
accommodation
as a monocular cue of depth percep-
tion the Drainos use of information
aDout the changing thicMness of the
lens of the eye in response to looking
at oDLects that are close or far away.
distant mountains often look fuzzy, and buildings far in the distance are blurrier
than those that are close.- Te x t u r e g r a d i e n t : If there are any large expanses of pebbles, rocks, or patterned
roads (such as a cobblestone street) nearby, go take a look at them one day. The
pebbles or bricks that are close to you are very distinctly textured, but as you
look farther off into the distance, their texture becomes smaller and finer. Te x t u r e
gradient is another trick used by artists to give the illusion of depth in a painting. - Motion parallax: The next time you’re in a car, notice how the objects outside the
car window seem to zip by very fast when they are close to the car, and objects in
the distance, such as mountains, seem to move more slowly. This discrepancy in
motion of near and far objects is called motion parallax. - Accommodation: A monocular cue that is not one of the pictorial cues, accommo-
dation makes use of something that happens inside the eye. The lens of the human
eye is flexible and held in place by a series of muscles. The discussion of the eye
earlier in this chapter mentioned the process of visual accommodation as the ten-
dency of the lens to change its shape, or thickness, in response to objects near or
far away. The brain can use this information about accommodation as a cue for
distance. Accommodation is also called a “muscular cue.”
texture gradient
monocular depth perception cue, the
tendency for textured surfaces to
aRRear to Decome smaller and finer as
distance from the viewer increases.
Interactive