Purpose of this TIPS

A lot of people draw clouds in their illustrations based solely on intuition.

 

Even if you use a reference photo as reference and draw it as is, it doesn't mean you understand what a cloud is before drawing it.

 

If you properly understand the scientific nature and appearance of clouds floating in the sky, you can use this as a great reference when drawing them and take your expression to the next level, right?

 

That's the purpose of today's tips.

Distant clouds near the horizon

First, one technique for drawing clouds in the sky in illustrations and landscape backgrounds is to draw a rough grid in the sky and then arrange the clouds along that line.

 

This grid doesn't need to be drawn as precisely and accurately as when drawing man-made objects.

This is because clouds are natural objects whose shape and arrangement are vague.

First, you just need to draw the clouds on a generally flat surface, but take a look at the area circled in red.

Depending on the weather that day, you may see clouds overlapping in a complex way close to the horizon, almost seen from the side.

 

This is the only part that needs to be drawn three-dimensionally.

 

However, this kind of thing does happen because the clouds are quite low in the sky.

As you can see, if there is a mountain nearby, it will be hidden.

With an elevation angle of 10 degrees, the clouds in this position will be completely invisible.

Still, with a mountain of this size, it has a looming presence, which means, at least in Japan, you could say it is a landscape that is typical of the mountainous countryside.

 

The fact that the terrain hides the complex clouds near the horizon means that it is a location with a difference in elevation. If there is a mountain, it becomes a rural area.

High clouds

Clouds are roughly classified into three types according to the height at which they form: low clouds, mid clouds, and high clouds.

 

High clouds include cirrus, cirrocumulus, and cirrostratus.

Mid-level clouds include altocumulus, altostratus, and nimbostratus.

Low clouds include stratocumulus, stratus, cumulonimbus, and cumulonimbus.

 

These ten types are classified into ten types of cloud shapes. If you divide them further, it is said that there are 400 types, but unless you are an expert or a hobbyist, there is no need to memorize that many.

As an artist, you can become good at drawing the sky if you can draw 10 types of clouds while looking at reference materials as needed.

If you want to draw as accurately as possible, it's best to use three layers of grids - top, middle and bottom - as a rough guide, but if you don't have the time to go that far, a single layer of clouds will do, and even if you want to make it a little more luxurious, two layers of grids will enable you to enhance the appearance of the picture with minimal effort.

 

This is just the cotton clouds at the bottom added to the cirrocumulus and cirrus at the top, but as an expression of clouds on a sunny day, it is probably more emotionally appealing than cumulus clouds alone.

The shadows on the clouds look strange...? That's because they are colloids.

When observing the shadows of clouds, do you feel something is off?

No matter how you look at it, the rules are different from the shadows of objects we are familiar with. Something seems strange.

For example, when you look at a cloud from an angle that is not exactly front-lit from the observer's perspective, but is not backlit either, you will see a shadow like this near the middle of the cloud.

This is "strange" in light of the rules of light and shadow that we are familiar with, but since this is always what you see when looking up at clouds floating in a clear sky under the same conditions, it cannot be a strange physical phenomenon.

 

So why does this happen?

That's because clouds are colloids.

A colloid is a mixture of particles that make up a gas/liquid/solid and larger particles.

Familiar examples of this include milk and muddy water.

It's safe to think of the larger particles as "turbidity."

Clouds are a mixture of air and much larger particles like water droplets and ice particles.

Now, if we were to mention important points about how clouds appear, they would be the properties that "colloids look cloudy" and "colloids scatter light."

I think we can intuitively understand that they appear cloudy.

 

Speaking of clouds, they are white.

However, this white is not the base color of the cloud itself.

They appear that way because of light scattering.

 

Colloids that scatter light appear to be glowing. Famous examples that are beautiful to the eye include the Tyndall effect and angel's ladder.

 

The scattering that creates the white of clouds is called Mie scattering.

 

Rain clouds appear black because the scattered light is not visible from the ground due to their high density, and it may be better to think of the base color of the cloud itself as being similar to that of a rain cloud.

However, rain clouds viewed from above are normally white.

Clouds are low density and sparse, so almost the entire cloud scatters light, making it impossible to see shadows within it.

 

 

Now back to the clouds that look like this.

The light scattering caused by colloids attenuates the light extremely rapidly.

In other words, this shadow is caused by sunlight not reaching the center of the cloud.

And the way colloids that scatter light look is that the closer they are to backlighting, the more their transparency is emphasized by the amount of light and shadow.

No matter how much you emphasize it, it always ends up being semi-transparent, though.

The area circled in red appears white because it is the outer edge of the cloud, where the particle density is low and light is reaching it even though it is slightly opposite the sun.

Once you recognize this, the question of "Why does this cloud have such a shadow?" will be cleared up.

In other words, the shadow is visible because only the center of the translucent object is not shining.

Why the sky is deeper blue the closer it is to directly above

The blue of the sky is darker the closer it is to directly above, and appears whitish the closer it is to the ground.

So you can paint it that way on your art by using a gradation or an airbrush.

The reason this sky is blue is because the atmosphere scatters light.

This phenomenon, called Rayleigh scattering, is important, along with Mie scattering, in expressing aerial perspective in landscape paintings, so it's worth remembering.

 

So, why is it blue?...

The shorter the wavelength of light, the more likely it is to collide with air particles and be scattered, but purple is less noticeable to the human eye.

 

As a result, it appears blue.

 

The atmosphere near the earth's surface contains a lot of dust and water droplets, which cause Mie scattering, although not as much as clouds.

Therefore, the explanation for the phenomenon that the sky appears darker blue the closer it is to directly above is that the closer the angle is to directly above, the less whitish the sky appears due to Mie scattering.

Sakuei Summary

To summarise all of the above,

this is an example where the sun is slightly off-screen and to the right.

 

Thank you for reading to the end.