Perspective helps us recreate the specific way we see. Whenever we look at a three-dimensional object, you can be sure the following three rules apply.
Rule One: Convergence
All parallel lines that move back in space will always seem to converge at a point on the horizon.
The key word is seem, and it’s an important one. Parallel lines never truly converge, but as they move away from us they look like they do. It’s essential that you understand this idea as it exists beyond the specific object you’re drawing. All receding parallel lines, anywhere on the page, from any object, will always seem to meet at the same place on the horizon line.
Rule Two: Diminution
Objects of equal size appear smaller as they move away from the viewer.
As things move away from us, they get smaller on the page yet still represent their particular size anywhere in your picture.
Rule Three: Foreshortening
When an object that’s perpendicular to the viewer’s line of sight changes angle, the shape of the object seems more condensed.
When a form leans back, the part of the object that has moved forward starts to obscure what’s now behind it. Foreshortening effectively compresses how an object is represented. The more it leans back, the more foreshortened and condensed it appears.
How Perspective Works
Whenever we draw something representationally, we’re drawing what something would look like from a particular location. It’s a lot like using a camera – whenever I take a picture, what I get is determined by where I am in relation to what I’m looking at. If I move or aim my camera at a different location, I get a different picture. Representational artists create with the same intention – our work is always a portrayal of what things looks like from a particular viewpoint. When you look at a photo, you are essentially placing yourself in the photographer’s shoes – seeing exactly what they saw when they took the picture. Drawing serves the same purpose – what we draw and how we draw it effectively places our audience at the scene. The sole purpose of perspective is to help you do this accurately. To start, we need to define the three things that help us position our viewer in space: how high our viewer’s eyes are off the ground, how far away they are from our subject matter, and the direction or angle that they are looking in. The vocabulary of perspective is devoted to explaining how our viewer specifically relates to what he’s looking at. Once you understand the following ideas, you’ll have a much easier time navigating what’s to come.
Excerpt from Simplifying Perspective by Robert Pastrana © 2015 Focal Press an imprint of Taylor and Francis Group.