Two point perspective is our last major principle. This is pretty exciting, because with what you will have learned here you will be able to draw pretty much what you want to in terms of perspective drawing.
You will have suspected by now that rather than one place on the horizon line where the lines converge, there will be two: two vanishing points, hence two point perspective. We have a great example in the picture of the Arc de Triomphe above.
By the way, one thing you have to be careful of in two point perspective is the fact that you need a lot more room on either side of your subject to lay out the converging lines. Forgive the wobbly converging lines - my software just didn't want to cooperate. Nevertheless you can see that once you get those converging lines in place on the horizon line, you can see clearly that there are two vanishing points.
So what's the difference between a view of the Arc of Triumph in one point or in two point perspective? Answer: whether or not you have a flat facade or an angle facing you.
Now to draw the Arch like a glass box. We are going to begin by drawing the part of the Arch nearest to us: the angle jutting out to us.
First step: draw the horizon line, which runs pretty near the bottom of the Arch, as we saw above. In other words, if you are standing looking straight ahead at the Arch, your line of sight will fall pretty low on the structure. And then you need to place the line for the angle on it.
That gives us:
Now just like you did for the machine in one point perspective, you are going to use your pencil to take the angles, imagining that you are pressing the pencil against a pane of glass to set it along the lines of the Arch.
Just as we did before, you are going to now bring down your arm to your paper, holding the pencil carefully immobile in your hand so that you don't "lose" the angle. And now you are going to mark the angle in place on your piece of paper. Here's that illustration again of how to do this.
You will extend the lines all the way down to the horizon line to find your vanishing points.
Now it is just question of drawing converging lines from the bottom of the vertical to the vanishing points.
Now we draw the outside corners of the Arch by dropping vertical lines to "cut off" the converging lines where we want. If we look at the Arch of Triumph, we can see that the right side is a little more than a quarter of the left side.
You can now erase the construction lines to get the shape of the Arch now.
If we want to continue with our drawing to make it look like a glass box, so we can see the back of the Arch as if it were transparent, however, the next task is to draw construction (converging) lines from each corner to cross over to the opposite vanishing point, and to draw the back vertical.
Because the bottom of our Arch is sitting so close to the horizon line,
it makes it hard to see some of these new lines (in red) because they run so close to
the horizon line, although we can erase the construction lines and still get the glass box we wanted.
The technical drawing below will show more clearly what the result is, owing to the box being pretty far from the horizon line.
Once again, do I really go through all this when I'm drawing the Arch of Triumph? No.
However, I do have these techniques in my mental toolbox. And they come in handy when, for example, I'm drawing a table and I can't figure out why it looks funny.
If I find the converging lines, I can start to see why it looks funny. I have made the back left leg too long, and the right front leg too long as well.
By drawing the converging lines to construct my table, I can figure out what needs to be corrected, and get it right.