[Figure 7.2] The head moves down and up on an arc, using the eye as a point of reference.

Arcs
Nearly all patterns of movement occur along a curved path of action called an arc, rather than a straight line. Arcs are an important principle to pay attention to, and they are especially effective when applied to stop-motion animation. One of the biggest challenges in stop-motion is keeping each frame properly registered to the next one so that the movement is smooth. Because you are manipulating a puppet in three-dimensional space, it is very difficult to gauge exactly where the path of action is for any motion on the actual set. Making reference to what is on the monitor helps, and being able to place markers and use onion-skin features in frame-grabbing software makes a huge difference. But a frame grabber doesn’t understand how to animate, and neither does a computer—only an animator can understand this!

When planning out any movement, look for every opportunity to register your puppet so that the path of action it follows is an arc. You can draw this arc on your monitor or use markers in the software to establish where the points along the arc should be. Then, find a common point on your puppet that you can line up with this arc and keep it moving along that path as you animate. If the path of action does not travel along a steady arc and is not registered properly, the end result will be jittery. Even if one frame moves outside the path of action, it will be noticeable to the audience and create a small jerk in the animation. Having a path of action of any sort in mind during the animation process, whether you actually mark it on your screen or just picture it in your head, is vital to alleviating that “jerky” quality that often occurs in stop-motion. Basically, think hard about the direction things are moving. If a hand or head is moving to the right, keep it moving to the right until it’s supposed to change direction, perhaps up or down along an arc. A few frames (say six or more) later, it may even start moving to the left, depending on what’s actually being animated. Simply put, if you forget which direction your puppet is supposed to be moving, it will be all over the place, and you will inevitably get that jittery effect of a puppet on way too much caffeine.

[Figure 7.3] A hand with pointed finger moving along an arc up to the head.

[Figure 7.4] The ThunderBean, jumping along an arc path

of action.

Arcs can be applied to nearly any movement to give it more life and a natural flow. Moving a puppet’s head along an arc is effective when snapping into an anticipation pose, in any direction, and using the eye as a guide to move it along this path can be a useful point of reference (Figure 7.2). The same principle can be applied to a hand moving in space, using the finger or any part of the hand as a point to guide along its arched path (Figure 7.3).

For a character jumping, running, or walking forward, moving the entire puppet along an arc is very important to make the action smooth. An extreme motion like a jump will be even more noticeable if the frames are not registered along a steady path (Figure 7.4).