STRAIGHT AHEAD AND POSE-TO-POSE ACTION: 2D Animation principle

17 December, 2008

STRAIGHT AHEAD AND POSE-TO-POSE ACTION: 2D Animation principle

There are two main approaches to hand drawn
animation. The first is known as straight ahead action because the animator
literally works straight ahead from his first drawing in the scene. He knows
where the scene fits in the story and the business it has to include. He does
one drawing after another, getting new ideas as he goes along, until he reaches
the end of the scene. This process usually produces drawings and action that
have a fresh and slightly zany look because the whole process was kept very
creative. Straight ahead action is used for wild, scrambling actions where
spontaneity is important.

The second approach is called pose to-pose. Here
the animator plans his actions; figures out just what drawings will be needed to
animate the business, makes the drawings concentrating on the poses, relates
them to each other in size and action, and then draws the inbetweens.
Pose-to-pose is used for animation that requires good acting, where the poses
and timing are all important. The pose-to-pose technique applies to keyframe
computer animation with timing and poses control of extremes and inbetweens. The
difficulty in controlling the inbetweens makes it incorrect to approach keyframe
computer animation exactly as one would pose-to-pose hand drawn animation. In
working with a complex model, creating a complete pose at a time would make the
inbetweens too unpredictable. The path of action will in general be incorrect
and objects will intersect one another. The result is much time-consuming
reworking of inbetweens.

Some animation for television
were made on pose-to-pose basis because of budget constraints. In pose-to-pose
animation the purpose of creating and animating is served, but does not enhance
it. However animation for features demand more appeal., where pose-to-pose
animation does not serve any purpose of producing the feature. Pose-to-pose
animation is widely used for stylized animation productions.

There is a much better approach in the context of
a hierarchical modeling system, which works “layer by layer” down the hierarchy.
Instead of animating one complete pose to another, one transformation is
animated at a time, starting with the trunk of the hierarchical tree structure,
working transformation by transformation down the branches to the end. Fewer
extremes are used not all translates, rotates and scales have extremes on the
same frames; some have many extremes and others very few. With fewer extremes,
the importance of the inbetweens increases. Tension and direction controls on
the interpolating splines are helpful in controlling the spacing of the
inbetween and to achieve slow in and out. This layer approaches to animation
shares many important elements with the pose-to-pose technique in hand drawn
animation. Planning the animation out in advance, as in pose-to-pose becomes
even more important. The action must be well thought out, the timing and poses
planned so that even in the early layers, the poses and actions arc clear.

The Adventures of Andr & eacute and Wally B and
Luxo Jr. were both animated using a keyframe animation system called Md (Motion
Doctor). Luxo Jr. was animated using this layered approach to the key frames.
Jr.’s hop was animated by first setting the key frames for his forward movement
only, two key frames were set for the X translation, the first where the hop
starts and the second where he lands. This defined the timing of his hop. The
height of his hop was then defined by setting a key frame in the Z translation.
The next step, animating the rotation of Jr.’s arms, was important because the
arms define the anticipation, squash and stretch, and follow through of the
action. Key frames were set for just about every frame, rotating the arms
together before the hop for the anticipation, then immediately far apart for the
stretch of the jump. The arms were rotated together again at the top of the arc
where the action slows slightly, then rotated far apart, stretching to
anticipate the landing. To indicate the shock of the landing, the arms were
rotated quickly together two frames after the base lands on the floor. This is
the follow through of the action. His base and shade were animated in the next
two steps. Like the arms, many key frames were set to define the rotation of the
base and shade because their movement was important for anticipation and follow
through.

Straight Ahead Action: Straight ahead
action is so called because an animator literally works straight ahead from the
first drawing in the scene. This process usually produces drawings and action
that have a fresh and slightly zany look, because the whole process is kept very
creative. Straight ahead action is used for wild, scrambling actions where
spontaneity is important.

Pose-To-Pose Action: In pose-to-pose
animation, the animator plans his action, figuring out just what drawings will
be needed to animate the scene. Pose-to-pose is used for animation that requires
good acting, where poses and timing are important.

Relevance in CGI: Pose-to-pose action is
an important tool in computer animation. Objects are built in a hierarchy, where
each layer of the hierarchy has an associated transformation. Animation is then
built up one transformation at a time from one pose to the next. For example,
when animating a person walking, you would first set the pose position for the
hips at the start of the motion, and then you would adjust the hip translation
for the end of the action. Then building upon this original pose, you would
transform other objects in the model, until you had traversed the hierarchy. All
of your actions must be well thought out, and the timing and poses planned so
that even in the early stages, the action is clear.

Pose-To-Pose Animation Method:

‘Key poses’, ‘key drawings’ or just ‘keys’ are
terms used to describe those critical positions of an animated character or an
object which depict the extreme points in its path of motion, or accents in its
expression or mood. For this reason they are also called ‘extremes’. This method
of animating from one pose to the next, hence the term ‘pose to pose’ animation,
allows the animator to map out the action in advance with ‘sign posts’ by
charting up these key poses onto ‘exposure sheets’ or ‘dope sheets’, or indeed
into the timeline of computer software. It is a particularly useful animation
method when a character must perform certain tasks within a predetermined time
or where a series of actions must synchronies accurately with a recorded sound
track. The technique helps ensure that characters arrive at a particular place
on screen at a precise point in time.

The ‘key pose’ technique is still the most widely
used method of animating. It is also the method of choice within most 2D and 3D
digital animation packages these days. Sequences can be tested and individual
poses can be re-worked and the animation progressively improved. The exposure
sheet or timeline is continually revised to provide an accurate record of how
the animation is to be photographed or rendered. This production method also
provides a logical way of breaking down work so that it can be handed on to
other people in the production chain.

Working Rough:

When developing key poses, it’s a good idea to
experiment with thumb-nail sketches first to refine the poses and ideas.
Initially, the animator’s key poses may be nothing more than rough scribbles to
block out the action. This is often done with a blue pencil. There is no point
doing lots and lots of highly finished drawings at this stage if the action does
not work. Besides, working roughly and quickly sketching out the main shapes,
forms and lines of action knowing that these drawings are just a first step in a
bigger process, always leads to fresher animation.

Planning Key Poses:

Obviously when planning a set of key poses for a
shot or scene, the animator needs to be acutely aware of the requirements of the
script and the particular actions and events that are necessary to progress the
storyline. Background layouts will define an ‘acting space’ while storyboard
frames will indicate the ‘business’ of each shot. What is entirely under the
animator’s control is the way the character ‘acts’ out these events as informed
by an understanding of the character’s personality traits, visual design and
current emotional state. The key pose planning process goes hand-in-hand with
the idea of staging each action in such a way that it ‘reads’ well and
communicates clearly. Several key drawings might be required to describe the
sub-movements involved in even the most simple of actions – taking a pair of
socks out of a drawer, for example. If we were to go straight from the first
drawing of our character standing by the cupboard to the final position with
socks in hand, the result would appear as if a pair of socks had just magically
appeared in our hero’s hand. Obviously there is information missing which has to
be seen by the audience to explain just how the socks got into the character’s
hand.

To tell the full story we need to break down this
simple action into several steps. We need to see the character standing by the
cupboard, reaching for the drawer, pulling open the drawer, dipping a hand in,
and finally extracting the socks. Each of these poses, including squash and
stretch, anticipations and any poses which use exaggeration, are treated as a
separate ‘key pose.’

Expressive Pose:

Animation usually operates in the realm of
caricature in which exaggeration becomes an important factor in order to capture
the spirit of the action being depicted. Good strong key poses emphasize and
communicate the intent of an action more efficiently than ill-considered ones.
Put simply, strong keys lead to strong animation. It is therefore vital to spend
time and thought working out the key poses until they do their job as
expressively as possible as it will pay dividends as if these work well.
“Limited” styles of animation are based on keys only, and this labor saving
technique does not necessarily affect the audience’s enjoyment of a piece.

As animators work out the key poses of a
particular sequence, they also find it helpful to consider whether or not the
action works well if reduced to a silhouette. Staging the action of hands
gesturing immediately in front of the body may not be as effective as staging
this action in profile where the various shapes and forms can be seen in a way
that does not rely on the challenge of drawing complex foreshortening.

Poses should have both function – depicting the
physical extreme of an action or setting up the character for an action to
follow by loading its ‘muscles’, and impact – an expressive pose with a dynamic
quality that implies what has gone before, what is about to come, and which
registers and emphasizes the inner emotional state of the character. Animation
is an illusion requiring the audience to suspend its disbelief. The audience can
be absolutely engaged within the stories we tell and the world of characters
that we create. However the illusion is a very delicate one, and alas, it is all
too easy to remind the audience that they are merely looking at a series of
drawings, a puppet, or a moving computer model.

To sustain this illusion, in a sense, we also
have to infer the physical laws of our animated world in such a way that they
are not in conflict with our day-to-day experience of natural laws we observe in
the real world. These laws can be represented in an incidental way by how your
character moves about its setting. Your key poses, therefore, should also show
how the character carries its own weight – is one leg relaxed while the other
supports the entire weight of its body? Is the body of the character under some
physical strain from carrying, pushing or pulling a heavy object? Perhaps you
need shift the character’s weight off-centre to counter-balance the object it is
carrying. What is its state of balance or indeed unbalance? Consider the ‘line
of action’, the main mass of the character and what happens to these masses when
your character propels itself from a resting position – there must be at least
one firmly locked down a contact point with the ground (usually a foot) so that
the forces involved in getting your character moving can be seen to pass through
its body to this contact point making the action believable. The slippage of
feet upon the ground at inappropriate times is one sure way of shattering this
illusion.

When learning how to animate for the first time,
get up out of your chair and act out the action you are trying to represent.
Feel where your limbs are space, what you muscles are using, the contact points
you have with the stable environment, and how the weight of your body is being
supported. If you are all your key poses are correctly thought out and timed,
you will have no trouble in getting all your ideas across to an audience. Flick
your key drawings from one to the next to ensure that the poses you have chosen
work well together. It is usually only after all the key poses of a scene have
been timed out on the exposure sheet and tested, that the animator or their
assistant returns to add the ‘inbetween’ drawings.

In larger traditional animation studios, these
numbered drawings are handed on to an assistant to further clean up and refine
according to character model sheets. Once tested, an ‘inbetweener’ adds the
required number of drawings between each key pose as prescribed by the
animator’s dope sheets. A clean-up artist will tidy up all the drawings ready
for tracing. In digital production, a computer software package can inbetween
for you, but it does not follow that computer software understands how things
move in the real world. Key poses describe WHAT happens, but not necessarily HOW
it happens.


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