To avoid warped perspective, as shown in the first drawing of the bedroom, the vanishing points must be spaced widely apart. Norling doesn't provide a formula for how far apart exactly to place the points, but the spacing seems to depend on the size of the subject being drawn. If the subject is large, then one of the vanishing points may go off the page. Drawing the first vanishing point seems to depend on one's location relative to the subject, as shown in the two drawings where you get a different perspective of the bedroom depending on your position relative to the closest bed.

This drawing traces the movement of the vanishing points relative to each other as an object is spun clockwise. The first VP is A and the second is B. The superscripts indicate each turn of the object. The two vanishing points never converge. When you look at a square object face-on, you can only draw one vanishing point because the other extends to infinity along a line parallel to the eye level line.

The most important step in a perspective drawing is to locate the eye level line. Then, you can build rectangular objects by piling bricks. Below the eye level line, you can see three sides of the brick. Above the eye level line, the parallel edges of the top of the brick converge, so you can only see two sides and the parallel lines of these sides tilt downward to reach the vanishing point. In short, parallel lines below the eye level tilt upward to the VPs and parallel lines above the eye level tilt downward toward the VPs.

It turns out that there is an easy and methodical way to place people in perspective relative to a building. First, locate the average height of a person standing right beside the building. Draw two lines passing through this point to the two vanishing points: this is the height line. Extend the base lines of the building. A person standing on this baseline would be as high as the height line. To find the height of a person not standing on this base line:

1. Mark a point where you wish this person to stand.

2. Draw a line from this point to the VP until this line intersects the base line.

3. Draw a line straight up until it intersects the height line.

4. From this intersection, draw a line towards the VP until this line passes above the original point.

5. Now, as you can see by the arrows, you have the height of this person.

1. Mark a point where you wish this person to stand.

2. Draw a line from this point to the VP until this line intersects the base line.

3. Draw a line straight up until it intersects the height line.

4. From this intersection, draw a line towards the VP until this line passes above the original point.

5. Now, as you can see by the arrows, you have the height of this person.