Drawing in perspective has a lot in common with taking a picture. Just like a photographer, we record what we want our viewer to see from a very specific point of view - we just do it as a drawing.
When working in perspective, we have three concerns…
Height To get this picture, the camera needs to be low to the ground. We can already tell the camera is lower than the chair, because we can see underneath of it.
In this picture, the camera was placed higher than the chair. In perspective, we need to have an idea of the height of our viewer’s eyes from the floor.
Viewing Angle When taking a picture, you can aim your camera in any direction.
We simplify that idea when working in perspective. Normally, we pretend we’re looking straight ahead. This makes working with perspective much easier, since slight changes in viewing angle don’t really affect our drawing. We use a perfectly horizontal viewing angle when working in one or two-point perspective.
There’s an important exception - if the viewing angle is either very high or very low.
Strong viewing angles change how things look in a drawing. When this happens, we have to work in three-point perspective.