Squash, Stretch, and Scale - Animation Fundamentals

Everything, everywhere is reacting to the physical effects of something. Even the items nonchalantly resting on the ground are having secret bouncing dance parties in reaction to the ground constantly smacking them with gravity.

Whether it's the physical effect of muscles deforming and altering the scale of body parts, or a hard metal ball bouncing on concrete, there will always be some level of scaling visually. That is, our eyes see motion blur, and all objects bulge (even if only a little) when they hit other objects. That said, it's important for animators to exaggerate these naturally-occurring phenomena.

Squash is the easiest way to create anticipation before a movement begins, especially a fast one. It's important to remember that preserving volume sells most animations with squash, so as things get squished, they should get wider in the other dimension. That matter has to go somewhere.

Preserving volume is really important for hard, solid objects, like anvils, pianos, and army tanks, less important for flexible objects like water balloons, tires, and jello molds, and totally unnecessary for objects like balloons full of air, t-shirts, and blow fish.

Another, obvious example of squash is when an object is literally being pressed by something. Not much description needed on that one, except that there are a plethora of slow motion videos of things being smashed on Youtube for your reference.

When animators talk about stretch, they're usually referring to stretching with preservation of volume. The other kind of stretching will be addressed in the module below.

Stretch can be the result of something being grabbed and pulled on by two conflicting forces, but the less obvious, more important kind of stretching is the kind that accompanies a quick movement, linear or on a curved path.

Stretch usually happens right after squash, the most commonly-used example of this is when a ball bounces or a character jumps. When the ball hits the ground and is about to fly back in the air, that's when it's in a 'squashed' position, and immediately after (when it has the highest velocity) is when it is stretching.

Other kinds of scaling include when objects are inflated/deflated, when the animator is purposefully messing with the audience, and the most important kind of non-volume-preserving scale: motion blur.

Motion blur is a byproduct of our vision, and of cameras. It is not a true physical effect, but a trick of seeing. It is also a very useful tool for an animator working on a time budget, because it can simulate a higher framerate than is actually there. Even with a high framerate, though, it looks very nice and can help bridge the gaps between frames of animation.