Perspective: Seeing where you stand
Perspective is the art of drawing so as to give the effect of solidity and relative distance and size.
Perspective is a word, but also a concept, describing how things look depending on where things are. Things that are closer to us always look bigger than they would if they were far away; a beetle can look bigger than a bus if the beetle is close enough, or the bus is far enough away.
Things also appear to change shape depending on where they are in relation to you (or where you are in relation to them). A table will look very different if you are standing on top of it, or sitting on a chair looking at it, or hiding underneath it. This applies to most other things.
Try looking at different things from different angles and distances in order to see how much they appear to change.
We know where things are because of their shape and size. We don't need to be able to draw, to be good at using our understanding of space. The only reason anyone can catch a ball, or kick it, or even find it, is because we are able to judge where it is, because of how it looks, and how it seems to change shape and size as it moves. Even animals are good at perspective, otherwise dogs couldn't catch sticks.
The problem with perspective is not using it, but using it so that drawn pictures of things look right - drawing things "in perspective".
Artists learnt to use perspective a few hundred years ago. If you look at old paintings - before the 15th century - you will see that most of them are pictures of things on a flat background. There doesn't seem to be much space in them. You can see examples of paintings which have bigger and smaller things in them before the 15th century, but nothing that suggests depth or the use of "perspective" as an art tool. In Italy during the Renaissance, people started to wonder why things looked the way they looked, and to wonder how you could make pictures look more like the world we see around us. Some artists invented the system that we call perspective for describing things visually.
We use the same system today, in computer programs and design, this is because it still looks "right". But it is only a system for making things seem to look "right". You can make a drawing look like anything you want, you can take a picture of anything you want, but every time you do these things you are telling a sort of lie, because you are creating an illusion. We know that all drawings, paintings and photos are really just flat surfaces with marks on them. Perspective is only a system and some of the things about it aren't quite "right".
Anyone who has ever been to the seaside will have seen a horizon (as long as it wasn't foggy). This is the line you see far away, out to sea. It's the line where the water stops and the sky starts. There are horizon lines everywhere, but usually you don't see them because something like a hill or a tree or a house is in the way.
You always see the horizon line at your eye level. In fact, if you change your eye level (by standing up, or sitting down) the horizon line changes too, and follows your eye level. Your eye level always follows you around everywhere because it's your eye level. If you sit on the floor the horizon is at your eye level. If you stand up, it's at your eye level. If you stand on top of a very tall building, or look out of the window of an aeroplane, the horizon is still at your eye level. It's only everything else that appears to change in relation to your eye level. The fact is, that everything looks the way it does from your point of view because you see it in relation to yourself. So if you are sitting looking out of the window of an airliner everything is going to look shorter than you because at this moment you are taller (or higher) than everything else.
Everything always gets smaller as it gets closer to the horizon, or your eye level, because it's getting further away from you.
Your eye level is always on the horizon line because what you are really looking for is the edge of our planet where it begins to curve out of sight. If you go to the seaside, you will sometimes see ships disappearing over the edge of the horizon. If you are higher up you still see the horizon, you are just looking a bit further over the edge of the world. Because the world is round, the horizon line is really a curve, but the world is huge, so this curve is so big that it looks like a straight line.
Here's something you can try for yourself:
Go and find a long straight wall. A corridor is best, but a long brick wall is good, or even a straight fence. If you look straight at it, the top of it will be horizontal and so will the bottom. But if you look along it, what happens to the line of the top of the wall, as it gets further away from you? Does it look like it goes down, as it gets further away from you? Now look at the line of the bottom of the wall and see what happens to it, as it gets further away from you. Does it look like it goes up, as it gets further away from you? The line at the top goes down because it's above your eye level. The line at the bottom goes up because it's below your eye level. Now if the line at the top goes down, and the line at the bottom goes up, then there must be a point somewhere in the distance where, if the wall was long enough, these lines would meet. At this point, of course, the wall would have to be so far away that it would not just look really small, but would get so tiny that it would appear to vanish. This is called the Vanishing Point. The same thing happens to the floor (or the street), and the ceiling (if there is one), and they all go to the same vanishing point. (This is an example of One Point Perspective)
Now if you crouch down while you are looking at this wall, can you see what happens to the lines at the top and the bottom of the wall? The line at the top gets steeper and the line at the bottom get shallower. This is because you have changed your eye level. Try this a few times and you will see it always happens.
Remember this rule: Everything that's higher than you goes down to the vanishing point, everything that's lower than you goes up to the vanishing point.
One Point Perspective
One point perspective is a drawing system in which everything gets smaller towards one vanishing point. Examples of these are if you are looking at a long straight street of houses, or down a corridor. If you think of the street then everything in the street gets smaller towards this one point. This includes the road, the houses to the left, and the houses to the right. If you are thinking of the corridor then the floor, walls and ceiling do the same thing. All go towards this one vanishing point.
Two Point Perspective
Two point perspective is a drawing system in which everything gets smaller towards two vanishing points; this is a better system because, in real life, there are also more than one. An example of this is if you imagine yourself on a street corner looking at the edge of a building. If you look down one side of it the wall on this side will get smaller and appear to go towards one vanishing point, but if you look down the other wall on the other side you can see it will get smaller, but to a distance at right angles to the first wall. This is the second vanishing point. In real life there are thousands of vanishing points but, interestingly, you only need two points to suggest nearly all the others.
A distance point is really just another name for an extra vanishing point, but it also helps you to work out a way of showing depth.
Imagine you are standing looking at a tiled floor. As the tiles get further away from you they get smaller. The left and right sides of the tiles get closer together as they converge towards the vanishing point (see definition for Converging lines). How this happens is covered in the headings for One and Two point perspective. But of course it's not just the sides of the tiles that get smaller, their backs and fronts do too. The question is: how can you make the backs and fronts of these tiles look like they are getting smaller as they get further away, in a regular way that looks right? Distance points are a neat way of sorting this problem out (see the exercise: Making a Perspective Drawing - steps 5,6, 7 and 8 - for how they work).
It doesn't matter why distance points work, perspective is only a system of drawing that makes things look right. Don't forget: all you are doing is creating an illusion - making a flat bit of paper look like it has got depth.
Three Point Perspective
Three point perspective covers the only vanishing points not represented in the other two systems: the point above your head and the point beneath your feet. Examples of these would be the way a tall building appears to get smaller: if you look up it from the bottom, or if you look down it from the top. You might ask why in that case we don't have a four-point perspective? But if you think about it the answer is obvious: we can't look up and down at the same time, so we don't need it.