Squash and stretch is a fundamental animation principle that involves the exaggeration of a non-rigid body's deformation as it moves, making characters and objects appear more dynamic, alive, and expressive. It's used to convey flexibility, weight, speed, and the impact of forces within an animated sequence, adding a crucial layer of believability and appeal to movement.
The Essence of Squash and Stretch
This principle isn't about making things look unrealistic, but rather about enhancing the feeling of realism and vitality. By distorting an object or character's form – squashing it down or stretching it out – animators can emphasize actions and reactions that would otherwise look stiff or lifeless. It creates an illusion of elasticity and responsiveness to external forces like gravity, momentum, and impact.
Understanding Squash
Squash refers to the compression of an object or character. It's typically applied to show:
- Force of Impact: When an object hits a surface, it briefly compresses, indicating the force of the collision and its material properties.
- Anticipation: Before a character performs an action, such as jumping, they often squat down slightly, "squashing" their body. This wind-up motion signals the upcoming action to the viewer.
- Weight and Mass: A heavy object will squash more upon impact than a light one, conveying its substantiality.
Example: A rubber ball hitting the ground will flatten momentarily before bouncing back up. Similarly, a character preparing to jump might compress their body downwards to build energy.
Understanding Stretch
Stretch refers to the elongation of an object or character. It's primarily used to indicate:
- Acceleration or Velocity: As an object speeds up or moves quickly, its form can stretch in the direction of motion to emphasize its velocity and momentum.
- Momentum: An object with significant momentum can appear stretched as it moves through the air, especially at the peak of an arc or during rapid movement.
Example: A falling rubber ball may begin to elongate as it speeds up, creating a sense of rapid descent. A character running at high speed might have their body and limbs stretched to convey their swiftness.
Why is Squash and Stretch Important?
The strategic application of squash and stretch enriches animation in several key ways:
- Adds Believability: It gives objects and characters a sense of volume, flexibility, and mass, making them feel more tangible and responsive to physical laws.
- Enhances Appeal and Expressiveness: Dynamic deformations make animation more engaging and allow for greater character expression, conveying emotions or intentions more clearly.
- Conveys Weight and Material: The degree of squash and stretch can suggest if an object is soft and pliable (like rubber) or hard and rigid (like a bowling ball).
- Communicates Speed and Force: Stretch emphasizes acceleration, while squash highlights impact and the build-up of energy.
The Principle of Volume Conservation
A critical rule when applying squash and stretch is the principle of volume conservation. While an object's shape changes, its overall volume should remain consistent. If an object squashes down, it should also widen to maintain its perceived volume. Conversely, if it stretches out, it should become thinner. This prevents the object from appearing to gain or lose mass, which would break the illusion.
Practical Applications and Examples
Understanding when and how to apply these principles is key to effective animation.
| Feature | Squash | Stretch |
|---|---|---|
| Purpose | Impact, anticipation, weight, sudden stops | Speed, acceleration, momentum, fluid motion |
| Direction | Compresses against the direction of impact/force | Elongates in the direction of motion |
| Visual Effect | Wider, shorter, heavier | Thinner, longer, lighter, more agile |
| Common Scenarios | Landing, hitting, preparing to jump, sudden stops | Running, jumping, falling rapidly, quick turns |
Here are common scenarios where squash and stretch are effectively utilized:
- Bouncing Ball: The classic example. The ball squashes upon hitting the ground and stretches slightly as it flies through the air, especially at its fastest points.
- Character Jumps/Falls: A character will squash their body before a jump (anticipation) and stretch during the ascent and descent, especially when moving quickly. They will then squash upon landing.
- Impacts and Collisions: When two objects collide, the impact point will often show a brief squash, indicating the force of the collision.
- Running and Sprinting: A character's limbs and body can stretch forward during a sprint to convey extreme speed and momentum.
Tips for Animators
- Don't Overdo It: The key is exaggeration, not distortion to the point of absurdity (unless that's the desired style). Subtle applications can be just as effective as extreme ones.
- Consider Material: The degree of squash and stretch should reflect the object's material. A rubber ball stretches and squashes more than a bowling ball.
- Maintain Volume: Always ensure that as you squash, the object widens, and as you stretch, it thins. This maintains the illusion of consistent mass.
- Think About the Action: Before animating, consider what feeling you want to convey. Is it a heavy impact? Rapid speed? Anticipation? This will guide your use of squash and stretch.
Historical Context: Disney's 12 Principles
Squash and stretch is one of the original 12 Basic Principles of Animation developed by Disney animators Frank Thomas and Ollie Johnston. These principles were codified to create more believable and engaging animation and remain foundational for animators across all mediums today.
