(1) Perspective drawing creates the illusion of distance through the fact that all lines
going away from the observer appear to come together at some distant points. For example, to a
person looking down a long stretch of railroad tracks, the tracks will appear to merge or disappear
(an illusion) at a single point in the distance. This point is called a vanishing point. It is one of
the three most important factors in perspective drawing.
(2) The second most important factor in perspective drawing is the station point. The
station point is the position of one of the observer's eyes (fig 2-8). The location of the station
point determines the perspective. For instance, a house is perceived differently at ground level
from the top of an adjacent three-story building.
(3) You should think of the object to be drawn as resting on a horizontal ground
plane perpendicular to the picture plane. The boundaries of the ground plane are two separate
lines, the ground line and the horizon line (fig 2-8).
Figure 2-8. Perspective nomenclature
The horizon line is the third most important factor in perspective drawing. Objects may appear
differently, relative to their position above or below the horizon line (fig 2-9). Notice how circles
of an angle appear as ellipses. The angle at which they are seen will determine their narrowness.