Making a TED-Ed Lesson: Animating zombies

You might remember a pair of TED-Ed Lessons written and performed by two educators, Brad Voytek and Tim Verstynen. These two scientists used a drooling, hag-faced, animated zombie as a mechanism to model the symptoms and medical diagnosis process for various neurological conditions.

For example, they spent time debating whether the zombie's stiff gait was caused by basal ganglia damage, like that in Parkinson's patients, or by severe damage to the cerebellum, which can cause ataxia. In each Lesson, Brad and Tim certainly showed us how the walking dead can help us understand neuroscience, but how can the walking dead help us understand animation? Or, more simply put, how did this one-eyed, decaying, and very much dead pile of pixels walk?

Puppet animation is a relatively quick solution to creating 2-D animation of a hand-drawn character. Since the character does not need to be drawn over and over again, it can be animated by moving each element individually. Aside from their portrayal in a few great modern zombie flicks, these concocted carcasses are generally known for limited, stiff movements. Their traditional stride is perfect for puppet-style animation.

When designing a 2-D zombie puppet, or any other type of puppet, it is important to find a design that is both fun and functional in a flat environment. For example, you might not want to puppetize, say, Julie Andrews in the "Sound of Music" as she spins in circles. We used rotoscoping for her, but that's another lesson.

Always begin by sketching and designing your puppet in a neutral pose like this. This will allow it to easily transition into and out of a variety of extreme positions. Once a character transitions from concept sketches to final design, the next step is to break up the pieces in order to assemble a puppet, keeping in mind that each element needs to have an appropriate amount of overlap so that the Zombie can bend at his joints.

An understanding of anatomy is an integral part of designing any 2-D or 3-D animated character that needs to move realistically in the context of its environment. Regardless of the number of dimensions your character has, you'll need to create a skeleton, which in animation terms is known as a rig. Once the rig is finalized and the range of motion is determined, the next step is to choose anchor points.

Each piece of artwork has its own anchor point, which essentially assigns the limb a hinge, which in this case is a joint. Next, line the artwork up so that the anchor point for the forearm-elbow sits on the upper arm's elbow area. Once all the artwork is in place, you can use an expression script that creates links between the body parts. In this case, we used the expressions provided in After Effects.

By parenting one layer to another, you could teach the forearm to follow the upper arm and the hand to follow the forearm. This is what's called forward kinematics. The alternative is inverse kinematics, in which a separate set of scripts control the motions. In this case, a controller is attached to the anchor point of the hand.

The animator then uses the controller to position the hand. The scripts will then use an algorithm to make sure that the rest of the arm and body follows along. Once the character is rigged, we can start animating. Often times, puppet animation is done as straight-ahead action, which means moving a character frame-by-frame from beginning to end.

Another approach is pose-to-pose animation, which involves choosing your key poses first, and then filling in the intervals, or in-betweens, later. Regardless of the method of motion, it's important to think of your 2-D puppet as a piece of paper. It can move across a surface in a variety of poses, but it cannot move in perspective.

If your character needs to turn its head, then you will need to create additional art. We created three different zombie heads and six different hands to achieve different movements and angles that the neutral pose couldn't accommodate. You can recreate almost everything you've seen in this Lesson with a pen, paper, and a camera.

The method is called cut-out animation, and it was around well before the age of software. To create a stumbling 2-D zombie, or a speeding narwhal, or even an abstract character with some semblance of joints, simply print, cut, and fasten your character's limbs together in a neutral pose. You can use fasteners, string, or even just place and move them each time.

All the same rules and theories that we use in the computer apply to cut-out animation, except under the camera, the only way to animate is straight ahead.