VFX: Smoke #1- Shape theory
Table of Contents
The thought process
Before we dive into any technical walk-throughs, lets uncover the underlying principles of smoke. This way, we can have a deeper understanding of WHY smoke behaves the way it does. Lets get started!
The science behind smoke
Animation is science, VFX is physics
Believe it or not, visual effects has an extremely strong correlation with physics. Its up to us as artists to interpret them into stylized effects.
Lets do some basic ‘bro-science’ deductions to understand smoke better.
What is smoke?
Smoke is a mixture of gases originating from a variety of sources. They tend to originate from a burning of materials such as wood, liquid fuels, organic material, and so on.Â
Why does smoke move?
Smoke moves away from its energy source (burning of material or kinetic energy). As it travels further away, it loses its heat and kinetic energy causing it to slowly dissipate into the atmosphere.
How does smoke move?
Gas has no shape and volume so there is little to no resistance when it floats around. This causes it to move in a ‘smooth’ manner- it accelerates and decelerates at a consistent rate.
How is smoke visible?
Smoke is visible because the gases that make it up are different from the air around it. Think of it like food coloring in a cup of water. The smoke’s color, value and opacity are tied to its fuel source and density.
Round with no sharp edges
No sharp, pointy edges
Smoke is round and moves smoothly. Sharp edges contradict this nature of smoke.
Try your best to round out shapes using shape and color.Â
For example, the diamond shaped image on the bottom right should be rounded off to a more square shape. The protruding pixels on the top and right side should be erased & smoothed out.
The top-left sprite can work but the length of the edges are extreme. Simply erase the extremities to make the sprite look rounder.Â
The bottom left example also has a random pixel sticking out on the top. Even after removing the top pixel, the sprite is literally a rectangle. Add direction to the shape by erasing the top-right pixel. It makes the right side look like a trail, which implies leftward movement.Â
Lets translate these concepts into pixel-art!
Avoid protruding pixels
Protruding pixels should be avoid whenever possible. This rule becomes more important as the resolution gets lower.Â
There are exceptions to this rule- its all about the context of the shape relative to the animation.
I like to use sharp shapes when the smoke starts to dissipate quickly. It only appears for a single frame or two at a high frame rate so it isnt as noticeable. But try to stay away from extremely sharp shapes.Â
That about does it for this post. Ill have a GIF-tutorial referring to this topic in the future- join the discord or mailing list to stay updated.
Thanks for reading & hope to catch you on the next one! -j
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