CLUES TO DISTANCE
Relative size of known objects is often used to provide a clue as to their spatial arrangement. In the top drawing at the right, the man appears much larger that the elephant and thus must be hunting the antelope while the elephant is located on a distant hill.
In the bottom view, the elephant appears much larger than the man and we assume that he must be close. Therefore the elephant is the quarry of the hunt.
Here we see two effects. The parallel lines of the windows in
the hall appear to approach each other; thus the right end of the hall must be more
distant. Likewise, since we assume that the windows are actually the same height,
the man on the right must be taller. (As explained on the optical illusion page, the figures of
the men are the same height.)
The four figures below indicate how an increased density gradient can be used to indicate increasing distances. If objects are at regular intervals they appear to be more dense at a distance because more of them are included in out field of view if we are farther away. Trees, blades of grass, parked cars, people in crowds, or any other sets of objects can exhibit this phenomena.
