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Animation: The Mechanics of Motion

Q. Will the object you are animating begin to move in its entirety at the same time?
Q. Will all aspects of the object you are animating stop at the same time?
Q. Do the secondary objects within your animation follow naturally on from the primary
animation and do they possess their own varied timings?
Q. Is the apparent weight of the objectreflected in the nature of its overlapping action?
Q. How will the object’s material affect the level of overlapping action?
Q. Is the flexibility of the material properly illustrated within your animation?
Q. How does the structure of the object suggest the level of overlapping action running
through it?
Q. Are there any loose garments, long hair or other objects in your animation that will beaffected by drag?
Q. Is the level of drag and follow-through appropriate to the effect you desire?
Q. Does the drag affect the limbs of the figure you are working with and if so how
appropriate is that to the suggested weight of the figure?

ARCS AND CURVES, AND LINE OF ACTION
Arcs and curves
In nature things seldom move in straight lines and most
naturalistic actions follow a series of veryoften complex
curves and arcs. Linear motion is not very often witnessed in
nature; such actions belong much more in the world of
mechanization. You should bear this in mind when making
either cartoon or naturalistic animation; just because you may
be creating cartoon-type animation it doesn’t mean you
should ignore the way things move in nature. Your audience
will buy into what you aredoing if your animation conforms
(more or less) to natural laws of motion and they recognize
the way things should move. However, there are times when
you may wish to give your animation a linear motion as a
result of design or aesthetic considerations, but this is a
different matter entirely. John Kricfalusi used this approach to
great comedic effect in the Ren and Stimpey series, taking adirect route from key to key, often ignoring arcs and slow ins
and outs to achieve a very snappy action, with all the
emphasis placed on the keys and not on the movement.

Basic principles

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Figure 1.59 The motion of an
element of a figure may take its
movement from the restricted nature
of the action – the motion of a
forearm being constrained by the
fixed position of the shoulderand
elbow will result in the arcing of the
hand as it moves along its spatial
plane.

Figure 1.60 In this throw you can
see that the arm describes a very
definite arc. The position of the
inbetween drawing is not obvious
from a simple animation breakdown.
If the animator were to be literal
about the breakdown, the result
would be very different and totally
unbelievable.

This doesmean that the keys have to be particularly strong
and interesting. Linear action will result in more punchy
actions and on occasion you may wish to disregard what
would happen in nature and take a little artistic licence (after
all, that’s what you’re there to do) to give the action more
power.
Complex animation that has many separate components,
such as in a figure running or a horsewalking, will describe
many arcs throughout its various elements, which on the face
of it can be most confusing. Just remember the work you did
for the bouncing ball animation and the arcs described there.
Treat each of the elements separately, starting with the
primary animation and moving on to the next stage; apply the
arcs to each of the elements in a structured way. Once you
have done this,go back and check on your animation as a
whole, making amendments as necessary.

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Animation: The Mechanics of Motion

Figure 1.61 When animating a head turn you will find that you get a much more satisfactory result if you arc it
slightly. The linear head turn looks unnatural and stiff.

Line of action
Creating a line of action is really only appropriate for
animators making 2D...