OPTICAL ILLUSIONS
Optical illusions are the result of using "clues" to interpret the content of an image. For example, the image shown at the right depicts two lines. The bottom line appears longer than the top because of the direction in which your eyes are drawn by the arrows.
Another example are the two sets of circles shown at the right. Although both center circles are the same diameter, the one surrounded by smaller circles appears larger.
In the illustration at the right both sets of lines are actually
parallel. However, in the top picture they appear to be closer together in the
center while in the bottom view they appear to buldge farther apart. This effect is
caused by the diverging and converging rays in the two pictures.
In the
picture at the left, the men appear to increase in size. Actually, all are the same;
however, the dimishing size of the windows in the hall indicate that the distance from the
viewer is increasing. Since we expect the windows to be a constant size but shown at
a greater distance, we assume that the figure is larger.
The Dutch
artist, M.C. Escher (1898-1971), specialized in scenes which appear to be impossible
because of "tricks" of preception. Objects which appear to be three
dimensional seem to be arranged in configuration which are not possible. One of his
drawings, The Waterfall, is shown here along with a similar type drawing.
When three dimensional objects are shown in a two dimensional drawing several unusual effects can present themselves. As shown below, the 2-D representation is not unique and can represent more than one 3-D view.
This effect can be used to produce the illusion of 3-D objects in a 2-D drawing. For example, look at the illustration below. By using a series of two dimensional drawings, each slightly changed, an illusion of three dimensional motion may be obtained.
