How perspective drawing is defined in Wikipedia:
[quote_box_center]”Perspective (from Latin perspicere, to see through) in the graphic arts, such as drawing, is an approximate representation, on a flat surface (such as paper), of an image as it is perceived by the eye.[/quote_box_center]
The two most characteristic features of perspective drawing are that objects are drawn:
* Smaller as their distance from the observer increases
* Foreshortened: the size of an object’s dimensions along the line of sight is relatively shorter than dimensions across the line of sight (see later).
I believe this is a very good definition of perspective but a bit cryptic.
Let’s break it down and try to make deep sense of it. Knowing what perspective is represents the first step to apply it effectively in your drawings!
Let’s use the help of Bob, the sticky figure to do this!
Here is Bob the stick figure looking at a big block of… material. However, he is slightly taller than the block itself and from his standing point he can see clearly the top part of the block. This is diligently shown in the second half of the above picture. That drawing is representing how Bob is perceiving the block.
As you can see, Bob has a fair perception of the frontal size of the block and he might be able to judge the relative length of the sides of the block in front of him. However he has a terrible perception of the depth of the block! If he had to judge the depth from his perspective he would probably get it completely wrong!
It is not poor Bob fault, in fact, this is due to the perspective perception Bob has of the Block. What Bob notices by looking at the block is that the lines that are parallel to the line of sight have been foreshortened compared to the lines transversal to the line of sight.
They have been shortened by the perspective!
Let’s go to the second images. Here Bob is trying to understand why that happens, why he has this perception of reality! He approaches an easier object to study, a lamp-post. A lamp post has no relevant depth; it is similar to a stick, so there are fewer things to consider.
Bob looks at the two identical lamp-posts, 1 and 2 which are positioned at different distances from where he stands and notices that the lamp-post number 2 appears to him smaller than number 1.
Clearly is the distance of the two lamp-posts from his position that makes the difference, but why?
Bob notices that everything he sees has to pass through his eyes or better through the pinhole of his pupils to get to his retina where the images of the lamp post are projected. It’s inevitable that the further away an object is from his eyes, the smaller the angles that object forms with his pupil. So A > B for the two distances.
If you think about it for a second, if we pushed the lamp post 2 further away from Bob it would became smaller and smaller to him until it’d disappear. Vanish. But let’s talk about this later.
Let’s continue with our exploration of perspective drawing..
Ok now Bob has understood that things close to him appear bigger to things away from him. Why is that so? Why can these things help us with perspective drawing?
The reason lies in the fact that things looked under small angles are projected onto Bob’s (and ours) retinas with small angles and things observed under bigger angles are projected with bigger angles. If A > B outside of Bob’s eye it stays so inside too. This is why Bob keeps perceiving identical object different if they are at different distances from his eyes.
Bob realizes that our brain has only one way to estimate the size of an object and that is by evaluating how big its projection on the retina is. So two identical objects seen under different angles will be considered by Bob’s and indeed our brains having different sizes.
[quote_box_center]This is the illusion of perspective! That’s exactly the same illusion you will have to set up when you are creating your perspective drawing![/quote_box_center]
The last aspects we want to explore before calling it done is the vanishing point. The vanishing point is crucial in perspective drawing and it is very important to understand in order to comprehend perspective.
Let’s get back to Bob for a sec. So he is looking at the lam posts. Now we take one of the lamp posts and drag it away from him. Bob will see the lamp post getting smaller and smaller obviously because he is looking at it under a smaller and smaller angle.
The lamp post is really small now and Bob hardly sees it at all. Suddenly Bob cannot see it anymore. That’s it! That is the vanishing point. The angle under which bob is looking the lamp post is so small that the image on his retina is smaller than the smaller thing his retina can detect. That’s the limit of Bob’s optical resolution!
Has this vanishing point a physical location?
Well yes and no. It is conveniently located on the horizon but the horizon itself is defined by your position above the water level. Normally the higher you are the further you can see but I do not want to complicate things now.
Let’s think of this vanishing point as a distance at which your power to resolve two different objects with your sight is equal to 0.
Consequently all the lines which are parallel to the line of sight will appear to converge to a vanishing point. It is obvious isn’t it? The two edges of a street… converging; two rails… converging… and so forth.
Wow it has been easy, hasn’t it? Now you have gained a very basic but solid knowledge about perspective and can move forward toward the understanding of how to apply perspective to your perspective drawings. You know why we see things in perspective and why perspective exists in the first place!
Moreover you know what a vanishing point is and why it exists. This is great!
I will see you soon in the next tutorials, have fun with perspective and spread the word!