STRETCH AND SQUASH: 2D Animation principle

17 December, 2008

STRETCH AND SQUASH: 2D Animation principle



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. This can
be related to Hooke’s Law F = -kx. Where the springiness or rigidity of
an object is, k the force constant and the amount the object was deformed would
be x.

Just as Hooke’s Law implies the
object must retain its volume or at least its density. If an object reduces in
size in the Y direction it should increase in size in the X 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).

The most important rule to
Stretch and Squash is that no matter how squashed & stretch out a particular
object gets, its volume remains constant. Consider the shape and volume of a
half filled flour sack when dropped on the floor; it squashed out to its fullest
shape. If it picked up, it stretched out to its longest shape. It never changes
volume. Stretch & squash also defines the rigidity of the material making up an
object. All objects change shape when a force is applied to them. Flexible
objects should Squash more and rigid objects squash less.



The best quality of an animated
character is its ability to transform into any shape and size, for example
classic animation of TOM & JERRY to DISNEY features, we notice the characters
have the flexibility to stretch to extreme positions and squash to unbelievable
shapes. The overall action looks appealing. In the early years animators had
great difficulty in animating complicated characters. As time went by they
realized, that a stiff character cannot be animated with ease and evolved a
formula where an animator could transform his character to any shape and size
but should maintain its volume. This means that during stretch and squash the
volume remains while the shape can change.

How It Works:

As we know animation is the
medium of exaggeration, and using exaggerated shapes can create the exaggerated
feature, these are nothing but stretch & squash. So with stretch and squash the
purpose of exaggeration is served. Before any kind of extreme action, the squash
position serves as anticipation.

Rigidity: The most
important animation principle is called squash and stretch. When an object
moves, its movement indicates the rigidity of the object. Many real world
objects have little flexibility, such as furniture, however most organic objects
have some level of flexibility in their shape.

Take for example a bouncing
ball. A rubber ball bounces higher and squashes more upon impact than a hard
league ball. The ease with which an object squashes and stretches defines the
rigidity of the material making up an object.



Volume: When a person
smiles, the shape of the face is determined by the movement of muscles
underneath a layer of skin. During a smile, though the head seems to increase in
size, with the widening of the mouth and jaw, it does not. The object is simply
displacing its matter into the stretched shape. The most important rule to
squash and stretch is that no matter how squashed or stretched out an object
gets, its volume remains constant.

Guidelines: The squashed
position depicts the form either flattened out by an external pressure or
constricted by its own power. The stretched position always shows the same form
in a much extended condition.

Varying Squash & Stretch:


Squash & Stretch:


Squash & Stretch:



Squash & Stretch:



Stretch & Squash action gives
the illusion of weight and volume to a character as it moves. Also squash and
stretch is useful in animating dialogue and doing facial expressions. How
extreme the use of squash and stretch is, depends on what is required in
animating the scene. Usually it’s broader in a short style of picture and
subtler in a feature. It is used in all forms of character animation from a
bouncing ball to the body weight of a person walking. This is the most important
element you will be required to master and will be used often.

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