The term squash and stretch describes the action of an object put under certain pressures. Push down on a rubber ball and it will squash; pull a sheet of rubber and it will stretch. However, squash and stretch does not simply apply to rubber balls or rubber sheets; it can apply to everything, or almost everything.
Most things in life possess a certain degree of flexibility. Certainly living flesh has a great deal of flexibility, no matter how bony the underpinning structure. The use of squash and stretch in animation allows for a degree of flexibility in all animated objects and figures. When a person smiles broadly, it isn’t just the mouth that moves—the whole face animates and demonstrates a high degree of flexibility. Everything from flexing an arm as it lifts a heavy object to a figure running or jumping will express varying levels of squash and stretch.
Let’s consider the movement of a very heavy character such as a giant ogre as he takes a stride. The entire figure may squash down slightly on impact, making him look heavy and cumbersome. Lighter characters, such as fairies, may need to demonstrate less squash, since they are infinitely lighter than giants.
Before animators began using this technique, animation was rather wooden, stiff, and awkward. When used clumsily, squash and stretch may result in all the animation flexing and bending with no real objective and to no real effect. Some of the early animators tended to flex all aspects of a figure almost indiscriminately, resulting in what became known as rubber-hose animation. This was because characters ended up with limbs with little or no structure—no shoulders, elbows, or knees, just bendy tubes rather like … well, rubber hose.
The use of squash and stretch may enhance movement, whereas in nature no such action would be evident. A bouncing ball on impact with the ground would clearly flex and squash downward, but as the ball begins its fall, its shape will remain spherical. However, if the animator chooses to add a little stretch to the ball on the beginning of the fall, the action of the fall is enhanced. Squash and stretch may even be used to good effect in animating objects where no squash and stretch could be possible. A little squash and stretch may be applied to quite rigid material such as glass or ceramic— material that would not normally be subject to squash and stretch. If this is done subtly, it will enhance the action. If it is overdone, which can easily happen, it will make the material look like rubber and will destroy the illusion. One of the key things to bear in mind in using squash and stretch is that although the object may deform in shape, it retains volume. In this regard it neither grows nor shrinks—it merely changes shape.
When taken to extremes, squash and stretch creates very cartoon-like animation, which may be very good for comedy effect but is less useful for naturalistic actions. The master animator Tex Avery regularly used squash and stretch in his animation to such extreme levels that the movement looked completely abstract. His almost unique approach to the animation principles makes his work distinctive and almost instantly recognizable.
Excerpt from Action Analysis for Animators by Chris Webster © 2012 Focal Press an imprint of Taylor & Francis Group. All Rights Reserved.