In this level we're taking a first look at fire by animating a steady candle flame.

Fire animation is quite simple as a single small flame. It only gets more difficult the bigger and "flamier" it is. Therefore, we'll start with a quiet candle flame. The candle flame is a manageable slice of physics and chemistry that can be studied and, when the day comes, applied to larger scale flames. We'll look at the various aspects in the following order:

• What is it?
• Design
• Timing
• Treatment

What is it?

Glowing particles of combusting fuel rise upwards, emitting heat and light, and eventually dying. These particles progress through stages towards inevitable expiry. At the start, they glow brightly, and rise quickly. But soon they lose their brightness and cool down. Just like all of us huh?

When no longer glowing, they are simply tiny black particles moving through the air. These "dead" particles of burnt airborne material, we know as soot. Clouds of soot, we know simply as smoke

Design

When you look at a fire, there seems to be a lot going on and it can be difficult to know where to start. The fact is that real world flames are of such complexity that, as 2D animators, we need to simplify this effect into a suitable 2D representation.

With that in mind, remember this: we need ONLY concern ourselves with what glows. Flame animation is about nothing more than those glowing sheets, ribbons and clouds of particles. Once they stop glowing, they're invisible and we forget them.

What about the smoke, you say?

In order to apply separate digital treatments to fire and smoke (i.e. glows and blur), it's necessary to animate the two effects on separate levels/layers. When animating flames therefore, don't concern yourself with the smoke. We'll animate that later.

Thankfully, a steady candle flame is one of the simplest forms of combustion we'll ever need to animate. In fact, the steadier the flame, the less animation. AND it can look just fine with minimal animation.

With the knowledge of what fire basically is, we are now armed with its basic rules of behaviour. From here, we know what we're drawing with each flame.

• We have a better idea of where the fire is hottest, and therefore brightest and fastest.

• We know that heat determines the areas of colour

• We know that, as flames move upwards, they must die and become smoke.

The design process is not just a nailing down of how it looks, but how that look is achieved. With the image of your finished product in your mind, what elements will your flame require? Several layers? Which layers have transparency, glows and blurs? Will the colours need to be on separate layers for special treatment?

Timing

Generally with a small flame such as that of a candle, simple is better. Matches and candles have a steady, constant supply of fuel to burn. Without a breath of wind a candle flame can appear motionless. Despite this, animators often feel the need to make candle flames flicker and dance constantly.

There's nothing wrong with having fun with your flame and making it do interesting things, but just be aware of overkill and distraction. If it's a romantic dinner for two, you probably don't want the candle flame thrashing about stealing the scene.

Steady

A quiet flame can be almost stationary for long periods of time, with the occasional flicker, roll or change in height. Subtle Candle is a perfect example on YouTube. The movement is so subtle at the start, you'll think the video isn't playing.

A really nice touch would be to work with other things in the scene. For example, in the romantic dinner scene, the flame could be almost motionless until the man picks up his drink.. a slight pause before the flame gently sways and resettles. Maybe the waiter arrives to stand at the table.. another slight pause, then the flame dips and waves a little more noticeably

Character animators breathe life into characters. FX animators breathe life into the characters' world.

One very interesting flame effect is a kind of swaying roll (image below). In fact, I saw it in action just today and was reminded to include it here. The flame was a tea-light inside a decorative glass tube. I don't claim to know exactly why this particular motion occurs, but I guess it's the result of an air current reaching deep into the tube and affecting the flame with a gentle circular turbulence.

Duck and weave

OK I could have called this one "squash and stretch" but this is a pulsing, swaying and oscillating of complex flame movement when you walk around the room holding a candle.

The duck and weave is an excellent exercise in flame animation and it's a lot of fun. Even with such a small and simple flame design, it seems no two drawings are the same.

Most important to be aware that a stretched flame should become thin, or break apart. Remember the fuel source of a candle is released at a constant rate. Also that when a flame breaks, that piece must continue to rise. And on such a small scale, these broken pieces are especially brief (as seen in the Flicker animation, above).