Not my images - I found these images on pinterest.com which always turns up a huge variety of reference and inspiration, whatever you search.

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Chaos forgives

When you start out as an FX animator, chaotic effects like electricity allow you to really have fun moving the arcs and lines around, snapping from interesting shape to interesting shape. This is one effect that actually benefits from "line jitter" which is the otherwise unfortunate result of inconsistent linework at high frame rates (something you'll learn about when you work with more subtle animation).

In a later article we'll look at flowing electrical arcs but for now we'll animate a lightning strike. Not only is lightning chaotic but it's very fast, so you can animate a number of lightning strikes in a fairly short time. You should be aware of some basic guidelines though. In this article we'll look at:

• Design - how to draw lightning
• Timing - animating it with realistic movement
• Treatment - colour and digital effects (glow, etc)

Along the way, we'll see some animated lightning scenes frame by frame, and near the end I'll give you an exercise or two to practise.

Design

Realism

I've always imagined lightning as a crack in the fabric of reality. As such, cracks in a plaster wall or concrete pavement can be excellent reference for lightning designs.

Cracks in earth, concrete and plaster can be excellent design reference for realistic lightning.

These cracks in a road surface make an interesting non-standard lightning design.

Cracks in concrete are an interesting and perhaps unexpectedly cool lightning reference, so when you see some fractured concrete, you might see a lightning design in there somewhere. A big part of FX animation is learning to observe the real world, but a master of FX design sees shapes, designs and possibilities that others don't.

Stylised

Quite often in animation we take liberties by exaggerating design, timing and/or treatment.

In the case of lightning, it's often effective if your design features some "thorny" bits (see image A, below). While it's not always realistic, adding these jagged shapes will help sell the untamed viciousness of the effect. Having curved, wavy shapes (see image B, below) will have the opposite effect, so it's perfect for those flowing, graceful electrical arc scenes.

A. B.

Weight variation

• As seen in any of the images above, your lightning designs should have a good deal of variation in the weight, or thickness, not just in the main bolt and branches, but also in the forks of the branches. When your digital glows are added, the flaring will be slightly more intense on these thicker parts. If you don't overdo it, this makes the whole effect nice and organic, rather than a consistent width glow all the way around.
• Mix it up - It seems that lighting in animation is commonly thicker at the source and thinner at the destination, but why not try mixing it up a bit? See what you can achieve by having a thinner bolt with some more thickness near the ground (see image A, below). Perhaps thin at the source AND destination, but thicker in the middle? (see image B, below). Experiment and have fun. Remember that you are the god of every scene.

A. B.
(image credit: stormscapesdarwin.com)

Timing

There are many types of lightning from huge sprawling branches to flickering bolts. Timing the lightning in your scene will depend on the effect you're going for. Let's look at two common types for now: bolts and branches.

Bolts

Electricity moves at the speed of light, which is 300,000km per second, so most lightning bolts look just fine if they "pop on" then quickly fade/flicker off (see example at Left).

Beware: if you animate a bolt "travelling" (i.e. animating into shot), even if it's just one frame, it will slow down the effect noticeably, reducing its impact. Sometimes this can be useful, for example if the scene requires you to "telegraph" the effect.

One other effective and simple technique is to flicker a bolt on and off twice on single frames, leaving the residual image in the viewer's eye to do the rest (see example at Right). Try it yourself!

Branches

Cloud-to-ground "branch" lightning often resembles an upside-down, skeletal tree. The intercloud variety (from cloud-to-cloud) sometimes gives the awe-inspiring illusion of creeping, almost in slow-motion across the sky. Even on such a massive scale though, it rarely and frustratingly lasts more than a few frames.

The big challenge is to animate that sprawl with enough grace that it appears slow, in turn giving the impression of vast distance. The key to animating something like this is to make the main body of lightning flow fairly gently, while the fingertips of the lighting creep outward, see example below.

Contrast

In the frame-by-frame sequence below (and it some of the examples above), you'll notice there is a completely black frame (2), followed immediately by a white frame (3). In animation, these are a black card and a white card, or simply "colour cards" (they can be any colour).

Using rapid, high contrast in this way is known to have a physical effect on the viewer's eye and brain. It's an incredibly useful technique, but also shamelessly abused. So many banner ads on the Internet these days have some kind of flickering effect to force your eyes in that direction. Don't overuse it! It's the visual equivalent of someone suddenly screaming into your face.

In effects animation, we use contrast not only with colour but also in other areas, like timing and volumes. The use of colour contrast in our lightning scene gives it undeniable impact. There will be a future article dedicated entirely to contrast because it applies in so many other effects.

A simple bolt sequence with frame numbers.

For some real inspiration, check out the timing in these amazing videos

Treatment and Filters

Really, you can do what you want with the colours of your effects. For the sake of realism though, let's assume lightning is a white-hot crack in the fabric of reality. Knowing that light directly into a lens causes flaring, we apply a glow or other "burning out" of the edge to give the impression of real light in the lens.

For my own lightning treatment, I like to do a couple of things. Firstly, I like to draw/paint the lightning in white. Regardless of the colour you want your lightning to be, nothing says "HOT" like a white core. Then, light, colour and heat are added using some glow filters.

NOTE: the image (right) is a gif, so those play controls won't work. However, if you have a SWF or Flash player on your computer, you'll find it in this chapter's files folder and you can frame-by-frame the animation.

Glows

My first glow is a broad, bluish-white. For fantasy, you can experiment with colour. Anything bright and saturated usually works well. If your software or medium allows you to control the glow falloff, you could try giving more intensity to the inner part of the glow, then fading outward. Otherwise, I would apply a second, tighter glow with a narrow blur radius. This is merely to give the lightning some heat and I often use red because that's the hot end of the spectrum.

Chromatic Aberration

Look closely at high resolution lightning photographs and you can often see a thin red edge on the left, and a thin blue/green edge on the right. Most VFX and compositing software has a filter called chromatic aberration which applies this effect. Combined with the other more broad glows, this is a very effective and subtle technique.

Assignments

Feel up to animating some lightning now? Here are some setup parameters and an FX layout to get you started on a single lightning bolt.

Everybody wants to add glows and light and make it cool; nobody can stop you doing that BUT REMEMBER: this is an animation course, and particularly at this early stage you should focus primarily on the design and timing. Again, resist moving on to the next phase until you're completely happy with the foundations. Good luck!

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Beginner

Suggested time to complete task: 5-10 minutes

A single lightning bolt of your own design.

1. Frame rate: 24fps

2. Duration: 2 seconds (48 frames)

3. Dimensions: 200 x 200px

4. The lightning bolt should start around 12-14 frames into the scene. Don't feel compelled to fill up the entire 48 frames with lightning. Make it look natural and don't be afraid to leave blank frames.

Intermediate

Suggested time to complete task: 15-20 minutes

Three quick lightning bolts coming from the same source position but striking in different locations.

1. Frame rate: 24fps

2. Duration: 3 seconds (72 frames)

3. Dimensions: 300 x 300px

4. The bolts should all start at the same position and each strike should be a different design and timing, giving variation and potentially some character to each bolt. Feel free to add sparks or any other scene elements.