Fundamentals of 3D Space - Flash 3D: Animation, Interactivity, and Games - page 162

provides the perspective drawing. Note that the projection rays can make the image on
the picture plane either larger than, smaller than, or the same size as the object itself.
Figure 6.1 Basic perspective projection
In computer graphics, the picture plane is generally assumed to be the monitor screen.
A line from the viewer's eye perpendicular to the picture plane is called the center of
vision (COV) of the perspective as shown in Figure 6.2. A horizontal line drawn on the
picture plane at the point of intersection of the COV with the picture plane is called the
horizon line.
Figure 6.2 Projecting a 3D point onto the picture plane