When the vanishing point is set below the object's vision, the result is a worm's-eye view of the thing from below (see Figure 3.74 on page 107). Depending on the number of vanishing points employed, there are three sorts of perspectives: one-point, two-point, and three-point. A one-point perspective gives a full view of the subject, with no foreshortening. A two-point perspective shows part of the scene, with some elements appearing larger than others depending on their distance from the viewer. A three-point perspective shows a slightly smaller portion of the scene than a two-point perspective, with three distinct objects visible at once.
In art school, we were taught about perspective by looking at pictures that already used it. Then, when we got our hands dirty and started drawing our own things, we could use what we learned. But now that we're teachers ourselves, we know that nothing can replace actual experience. So although studying perspective in photographs or drawings is helpful, nothing replaces actually going out into a scene and seeing how things relate to each other from all angles.
One-point perspective, two-point perspective, and three-point perspective are the three main forms of perspective. The numbers one, two, and three relate to the number of vanishing points used to create the sense of depth and space....
To depict an object in three-point perspective, three sets of orthogonal lines and three vanishing points are used. They form a third set of orthogonal lines that ascend from the ground plane to meet at vanishing point 3, which is high above the picture plane. These lines are called "sight lines." The two other sets of orthogonal lines descend from opposing corners of the subject and meet at vanishing points 1 and 2, which are below the picture plane.
Three-point-perspective drawings convey the illusion that everything not on the picture plane is further away from the viewer. This is accomplished by using visual cues such as distance, size, and angle to judge how far away objects are. Three-point-perspective drawings use all three of these factors to create the effect that things are farther away than they actually are.
In addition to making distant objects look smaller, three-point perspective also makes objects closer to the viewer appear larger. This is done by placing more emphasis on objects near the center of the image where most viewers will be looking. So although all the lines are equal in length, those near the middle tend to be shorter because they're being overshadowed by objects that are farther away.
Finally, three-point perspective draws attention to certain parts of the scene by having some objects rise above others.
The number of vanishing points used to generate the perspective illusion determines the three fundamental forms of perspective: one-point, two-point, and three-point. The most frequent is two-point viewpoint. Here the artist uses only two objects to represent a scene from different angles. They are called "vanishing points" because when viewed from the right angle, they seem to vanish into the background.
One-point perspective is less common but still useful in representing three-dimensional scenes in two dimensions. With this technique, all points on or near the apparent horizon line between the foreground and the background remain at the same distance from the viewer, while points farther away from this line appear to get smaller as they recede into the background.
Three-point perspective is the least common but also the most effective method for depicting realistic scenes. It uses three objects to create the impression of depth by having some faraway objects appear smaller than others. The artist must be careful not to have any objects overlap exactly, or the picture will look fake.
In reality, no such thing as a single point of view exists. We see the world from many different angles, which is why artists use more than one reference point when creating pictures that show perspective.