Clouds have volume and are subject to the rules of perspective.
|Clouds over Whiteface Mountain, oil on canvasboard, available.|
Clouds are not flat. The same perspective rules that apply to objects on the ground also apply to objects in the air. We are sometimes misled about that because clouds that appear to be almost overhead are, in fact, a long distance away.
I’ve alluded before to two-point perspective. I’ve never gotten too specific because it’s a great theoretical concept but a lousy way to draw. Today I’ll explain it.
|A two-point perspective grid. You don’t need to draw all those rays, just the horizon line. The vertical lines indicate the edges of your paper.|
Draw a horizontal line somewhere near the middle of your paper. This horizon line represents the height of your eyeballs. Put dots on the far left and far right ends of this line, at the edges of your paper. These are your vanishing points.
All objects in your drawing must be fitted to rays coming from those points. A cube is the simplest form of this. Start with a vertical line; that’s the front corner of your block. It can be anywhere on your picture. Bound it by extending ray lines back to the vanishing points. Make your first block transparent, just so you can see how the rays cross in the back. This is the fundamental building block of perspective drawing, and everything else derives from it. You can add architectural flourishes using the rules I gave for drawing windows and doors that fit.
A cube drawn with perspective rays. It’s that simple.
As a practical tool, two-point perspective breaks down quickly. In reality, those vanishing points are infinitely distant from you. But it’s hard to align a ruler to an infinitely-distant point, so we draw finite points at the edges of our paper. They throw the whole drawing into a fake exaggeration of perspective. That’s why I started with a grid where the vanishing points were off the paper. It doesn’t fix the problem, but it makes it less obvious.
All objects can be rendered from that basic cube.
(There is also three-point perspective, which gives us an ant’s view of things, and four-point perspective, which gives a fish-eye distortion reminiscent of mid-century comic book art. And there are even more complex perspective schemes. At that point, you’ve left painting and entered a fantastical world of technical drawing.)
Basic shapes of clouds using the same perspective grid.
Still, two-point perspective is useful for understanding clouds. Clouds follow the rules of perspective, being smaller, flatter and less distinct the farther they are from the viewer. The difference is that the vanishing point is at the bottom of the object, rather than the top as it is with terrestrial objects.
Cumulus clouds have flat bases and fluffy tops, and they tend to run in patterns across the sky. I’ve rendered them as slabs, using the same basic perspective rules as I would for a house. They may be far more fantastical in shape, but they obey this same basic rule of design.
|You can see that basic perspective when looking at a photo of cumulus clouds.|
A flight of cumulus clouds or a mackerel sky will be at a consistent altitude. That means their bottoms are on the same plane. However, there can be more than one cloud formation mucking around up there. That’s particularly true where there’s a big, scenic object like the ocean or a mountain in your vista. These have a way of interfering with the orderly patterns of clouds.
I don’t expect you to go outside and draw clouds using a perspective grid. This is for understanding the concept before you tackle the subject. Then you’ll be more likely to see clouds marching across the sky in volume, rather than as puffy white shapes pasted on the surface of your painting.