One point perspective. That's the name for where we are, now we have a good understanding of Principle 1, Principle 2 and Principle 3. In other words, when you have a composition with all the lines joining up at one point on the horizon line, i.e. at one place we call the "vanishing point", we call it a case of "one point perspective".
Now let's get clear the two simple but crucially important rules you need to do most of the drawings in perspective you will want to do.
Demonstration. Take a look again at my drawing of an Abu Dhabi cityscape. It is a bit different from what we have looked at so far, because while the vanishing point is indeed on the horizon line, its location is outside the picture frame.
Now if we draw red lines all along the obvious lines you can see and sense in the drawing, you quickly see that indeed, not only does the vanishing point (where all the lines join) lie outside the picture; all the lines above the horizon line are tilting down to it, and all the lines under it are tilting up.
If this rule seems hard to believe, get a pencil and just go to a window in your home and look out at the landscape.
As you look straight out the window, what your line of sight hits will be on the horizon line. With your pencil flat against the glass of the window now, rotate it until it seems to lie on any line you can perceive above or below the horizon line. You will see what I mean very quickly: lines above the horizon line do indeed tilt down, and lines above the horizon line tilt up. In fact, just identifying where the various lines meet to locate the vanishing point will also tell you where the horizon line is, as in the following case of Van Gogh's painting of his room in Arles:
Very simple, and what we already learned with perspective drawing and relative size, but it bears repeating - it will lead us to a fuller understanding of one point perspective.
In the below cartoon we have twin brothers and twin trees. Near is big and far is small.
But now let's take this concept one step further; it means that the front of an object (that is nearer to us) is going to be bigger than the back of the object (that is further from us). We can see that clearly in this photo of a piece of lab equipment:
If we draw a line on the front of the machine and another on the back of the machine, it's easy to see that the front near to us is bigger than the back far from us.
Let's draw this machine as if it were a glass box.
First, we draw a rectangle to represent the front of this piece of lab equipment we've taken for our subject. For our demonstration here we'll just judge the proportions by eye, a rectangle that looks about the height and width of the front.
We'll be assuming that the box is below the level of your eyes, i.e. below the horizon line. This means you are standing up and looking down at it, which is why you can see its top in the pictures of the lab equipment above.
Now you need to mark the vanishing point on your horizon line.
So imagine you are looking at the machine through a window, and imagine you are putting your pencil flat on the glass just like you did on your real window a little earlier in this section, holding your arm out straight. You place the pencil so that it looks like it is lying along each converging line of the top of the machine.
Now you bring your arm down to your paper, holding that same angle of line to your pencil, so you can see there on your paper where to draw it and and what angle.
You can see that where the two lines meet is about in the middle of the horizon line and the middle of your subject. So you mark that point on your horizon line: your vanishing point. This is the "one point" of one point perspective.
Now all you have to do to reproduce the lines you saw, is to connect the two corners of the front of the box to the vanishing point.
To find the other lines, you just connect the other corners to the vanishing point.
Now you have to draw the line of the back of the top of the machine. You can judge by eye, comparing it to the front of the machine to see if that looks like what you see "out there" in front of you. And you draw your line.
Draw the lines to finish the back.
Now all you have to do is erase the construction lines to have your glass box!
And you just have to erase a few more construction lines to have the shape of the lab machine:
In practical terms, when I need to draw a box, do I do all this? No. But I know how it works, and it gives me the tools I need to ensure that my box, whatever its dimensions, looks right - in other words, when it looks funny, I know how to fix it.
What we have done here will work just as well for you - um...as long as the front of the box in the drawing is facing you squarely as it does on this " one point perspective " page, that is.
Eh? What's that? What happens when the box doesn't have its front facing you squarely?
Time for Principle 4...