Squash and Stretch

Squash and Stretch help to define how rigid an object is. All objects change shape when a force is applied to them. Solid objects have so little that it can be ignored when you throw a bowling ball you won't see it change form or when you sit on a chair it does not change shape. These are rigid objects and in animation they do not change shape when force is applied to them. Objects such as a bouncing ball, or a pillow will change shape when a force is applied to them for example a rubber ball will flatten or squash against the floor when thrown against it and will stretch back up when it bounces off the floor.

This is number one on the list because in animation any thing that is alive will squash and stretch. Our muscles are constantly squashing and stretching with every movement that we make. Our feet squash and spread out when we put our body weight down on them. An animator could not make a person or an animal look real with out deforming the shape of the object that has force acting upon it.

The squash and stretch of an object can be thought of as the springiness of an object or material.Just as the laws of physics implies, the object must retain its volume or at least its density. If an object reduces in size in the one direction it should increase in size in the other direction. If this were not so the object would appear to shrink or grow.

An Animator can also stretch and object that is moving fast to make its motion seem smoother. When animating a baseball that has been thrown fast if the ball were not stretched it would look like a strobe effect not a smooth motion. When the ball is drawn so that each image overlaps the motion looks smooth (in real life a ball does not stretch, this is just one of the freedoms granted to an animator to help create the illusion of movement.) you can see this effect to an extent in the image below.

The above six images, from the movie The Emperor's New Groove (2000) produced by Walt Disney Studios, are an excellent example of the usage of Squash and Stretch. The bag Squashes to the shape of the steps followed by Cronk who dropped the bag when he stepped on a cat sleeping on the steps. In the last part you see the cat coming down after. The amount that each object deforms gives you an idea as to the rigidity of each object in the clip.