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Physics/Science of Light (PART 13)

(How you could implement it + create dramatic compelling art scenes)


Water is an extremely difficult medium to paint.

Colour of Water

Lets first talk about the colour of water.Water has a very unique way of scattering light, and the theory which supports this claims it has to do with the flexing of the 2 hydrogen molecules. (shown on first ball diagram) The theory behind it is that the vibration of H2O molecules cause the light that strikes them to scatter in unusual ways.

(refer to blue pic)

So as light, lets say sunlight,travels into the water-different colours are being scattered depending on the depth of the water.

So the reds in the light get absorbed at lower depths or volumes of the water while the blues get scattered.

However as you get deeper the deep volumes of water starts to absorb the green colours in the light and just scatter the blues in the light

And once you get very deep, the water starts to absorb the blues also and a great deal of the blue is lost however not to the point that it is lost completely. You must remember, this is the case with very great depths/volumes of water.

Colour of water


-What's underneath

-How much sunlight

-Suspended particles

Because of this process of scattering, anytime sunlight strikes into a body of water, there will be blues scattered in the water which causes us to see water as blue. The strength of blue that will be present is dependent on the depth of water and also what is underneath the water. Usually if you're in the middle of the ocean you won't see much underneath but the great depths of the deep blue water.

Suspended Particles

Suspended particles can change the colour of water. For instance, in this canyon, there's a great deal of lime coming out of it and washing into the water and the rocks, and its making the water even more turquoise than it would be considering its level of depth.

Usually the highest depths(shallow) water appears to be transparent /colourless. (first pic on buttom) However this is not the case for this river; the water seems to be more blue that it would be for its level of depth-suspended particles in the water are probably causing this.

We have the same case here, the mud washing into the river is making the mud brow. The means that the colour of the water depends on what it contains and what's getting into it.

Open Water

Waves travel uniformly outward from the location they were created.

Now we're going to be talking about open water. The way that water moves is an integral part of how it looks and how it responds to light.

First of all, water waves form from the energy transfer caused by leverage created by the water molecules groups bouncing off of each other.

The groups of molecules will form a chain by bouncing off of each other. It will produce a domino effect; which is a chain of reactions/cumulative effect triggered when one event sets off a chain of similar effects that follow.

These molecules will bounce against those molecules which will bounce against those molecules and so on.

When there's a single point of disturbance in the water, a ripple starts to form around that point and gradually move outward forming weaker ripples until there is no more energy to sustain the chain.

They form bow shapes with the rounded part forming the trough.

Intersecting waves combine: Troughs subtract and peaks add.

Waves will tend to form bow shapes with the rounded part forming the trough. Sometimes you'll see it appear a bit rounder on top. It's always a bit heavier on the bottom part of the trough. So what happens when there's waves that intersect with each other, (referring to 2nd wave) let's say I shifted these waves off from each other (and remember there's energy travelling in these waves).

and also the waves are transferring the energy downwards

r energy downwards, it also causes them to rebound back up. (refering to 2nd wave) Here's what's going to happen is, the energy of this wave, and the energy of that wave, (draw arrows pointing the waves in the 2nd wave pic) and the volume of water in it are going to add on top of each other, which causes a lower trough to form, (if you mix like this)and then a slightly higher wave with a flatter peak

and then a lower trough once more and so on.

(refer to 3rd wave) In this case where they're slightly offset the water waves which cancel each other out which will cause a very flat and calm surface to form.

Most bodies of water have chaotic, criss-crossing waves.

In most cases there will be waves in any standing body of water because it requires unique circumstances to make water appear so smooth like glass.

Even on this surface there's very subtle waves distributed throughout, this is forming a slight amount of distortion-even on this glassy surface.Even calm water usually has subtle ripples in the surface.

Waves take on a new character when passing over a sloped shore.Oceans have larger waves and the characteristics of those waves changes as they move to shore. As ocean waves pass over a sloped shore the wind blows across the surface of water and transfers its energy into the water. Then the water starts to pick up and rebound off of itself and create waves.

However, as the waves get close to the shore, the friction of the shore and the energy of the wave running into the shore forces the wave upward so the wave starts to get taller and higher. This friction on the shore pulls the bottom of the wave back, while the top of the wave topples forward with the same energy. The wave will crash into the shore and then run backwards.

White water is caused by reflective sheets of water and bubbles under the surface.Water is very reflective, and because of this when it starts to get churned up it starts to form bubbles.

When powerful waves collide with something, the rebound causes them to explode upward.

Caustics and Spectral splitting

Just like how glass can produce caustic effects-water also has caustic properties. Caustics are caused by the same process that causes refractions (add in link here) except it's happening due to the movement of energy in the waves.

(refer to diagram) How does this process occur?

As light travels in water, it will get redirected by the density of the particles in the water and also the by the strength of the waves it hits.

This will then create specific areas where the light is being focused and areas where the light is being scattered sporatically farther apart.

What will happen is you'll end up with some really bright spots and some darker areas. Shadows are being cast in the water as result of the movements of these waves. Similar to the caustic effect that's produced with glass or plastic, water refracts the red colour light a lot less and the blues considerably more. However the caustic effect produced by water is stronger in appearance because it is much more dense than air. Composition of the water affects reflections.The sun can create intense sparkling reflections even looking down.

Turbulence in the water also distorts reflections.

Flowing Water

Water has a tendency to work through the same process as convection currents. When water is flowing, it tends to move in circles that are in opposite directions-and they all affect one another.Rivers and streams are a combination of flowing water, ripples, waves, and whitewater.

Surface Tensions

Water tends to separate when there are turbulent movements, and what triggers this is called surface tension.

The H2O molecule has a slight polarity to it because of the positive charge coming from the two (2 little balls on top) hydrogen atoms and the negative charge of the oxygen atom. (big ball. oxygen) The polarity is also based on the way that the electrons are shared across the molecule.

Because of this structure,2 water molecules will tend to want to chain the negatives and the positives.

And when this happens they don't just chain together, they'll work in formations. Multiple molecules will bond together in formations forming networks due to this slight polarity.Water tends to want to cling to itself. And you can see this at a microscopic level, so when a water particle is standing on its own, instead of spread itself evenly over a surface,instead it's going to be pulling/exerting the force on to itself to stay together. And if I were to take a pin, poke the droplet and drag it along the surface, the droplet will stretch a bit following the pin while possibility still clinging to the pin. Water has a tendency to cling to things to some degree. If I were to continue pulling the droplet, it will stretch until it reaches a point where the force of the surface tension that's pulling the droplet back together exceeds the force that pulls it apart. Eventually, when this separation occurs, the water droplet will break into 2 separate beads of smaller droplets.

When water flows down a waterfall, the tension that happens with this contact, break into tiny little droplets. With an obstacle like a waterfall, the water is going to stretch as far as it can until it breaks apart into tiny little droplets which form a white overall appearance to the water. (like in the waterfall).

And you can see the type of patterns that are formed on the water from the turbulence that's occurring at smaller scale; the water is fighting a battle of trying to stay together as long as it can. And then as soon as the external forces pull it apart enough, it breaks into individual little drops. These drops can be large, they may be small but they are always trying to cling to each other. The larger the grouping of water, the easier it will be to break those large groups of water apart.

Even though everything is breaking apart, that tension that's trying to keep everything together causes foam and bubbles to form at the bottom of the waterfall.

Eventually it will create a mist that goes up into the air.

Water makes surfaces wet, this makes them shiny and darkened.

How to add water to your scene

Layer 1: Water shadow, wet surfaces, deposits, algae, etc.

Layer 2. Atmosphere effects

Layer 3. Caustics and Lighting

Layer 4. Reflections (multiple layers may be necessary)

Contact Points