Go To The Hop
I. Introduction-The Computer
One of the big advantages of using
computers in animation is the ability to easily find rhythms.
Frames are neatly labeled on a palette, and if you can count,
you can make events occur at very even intervals; your running
characters foot hits the ground every x frames,
your bouncing ball hits the ground every 2 seconds, etc....The
problem is, within those segments of evenly spaced instances
are fairly unevenly spaced series of motions. Perhaps one of
the biggest instances is the hop.
One sure sign of a beginning animator
is the computer hop; the object jumps, crests, and
lands all in the same fluid motion at the same speed. Its
easy to do. All the animator has to do is key frame the moment
the object leaves the ground, crests, and then when it hits.
Too often, this same evenly hopping object also remains fixed,
hard, and looking more like a ball-bearing than an animate object.
So, the purpose of this tutorial
is to examine what the anatomy of the hop really
is. The platform or animation application you use dont
really matter; the idea is to understand the motion of effective
II. Motion Analysis
First of all, lets look at
an example of what a computer-hop looks like. Animation
1 shows a chess pawn making just such a hop. Notice how
smoothly the hop goes; all perfectly one speed, perfectly timed
(Image 1), and perfectly phony. Notice how the pawn has such
a rigid look, that it doesnt appear to have anything thats
actually driving it up and driving it forward. It still looks
as if the animator is moving the piece rather than the piece
actually hopping. Although, this may be the look an animator
is going for, it usually makes for very unconvincing motion.
Eadweard Muybridge was a 19th century
photographer who in 1850 set up shop in San Francisco and worked
on landscape pictures. In 1872, railroad tycoon Leland Stanford,
former Governor of California, asked him to photograph his famous
horse, Occident to settle a long time debate over whether or
not a running horse ever had all four feet off the ground. Muybridge
used a series of glass plated cameras triggered by rubberbands
and wire to photograph the animal. His photographs of the flying
horse made him an international sensation. As his setup
became more complex, he was able to capture more and more series
of motion, including human motion. His subsequent discovery
that these series of images, when viewed in rapid succession,
produced what looked to be motion, earned him the title of "Father
of Motion Pictures." His exhibits inspired the likes of
Thomas Edison who soon began his own work on motion picture
Among Muybridges photography
are several series of people in the act of jumping. Through
analysis of these series of photographs, we can get a good idea
of the mechanics behind a body in motion. This sort of study
is very important in depicting a self propelled body.
Animations 2 and 3 give composited
animations (built by Charl Lucassen from Muybridge photographs
that give a good idea of a couple of different kinds of hops.
Although neither of these animations show the exact same type
of hop that we are creating in the Pawn animation, we can extrapolate
from the start of one and the end of the other the kind of information
that we need.
III. Object Orientation
Some very important concepts can
be learned from the non-composited Muybridge series of photographs.
Image 1 shows a breakdown of Animation 2. An aspect that seems
rather intuitive, but often forgotten is the idea that an object
orients itself in the direction that it is propelling itself.
One key element behind good motion, is that when an object is
in motion, it will orient itself in the direction that it is
moving. Image 2 shows that as the figure takes off, his head
is pointed in the direction that it is soon to travel. We can
see in Image 3 that as the figure reaches its crest, its orientation
shifts so that its feet are facing the direction the body is
shows our trusty pawn utilizing this concept and Image 4 shows
a breakdown of the pawns orientation in different points
of its flight. This motion is a good start and certainly better
than the original pawn animation, but still, the pawn is simply
too rigid to be believable.
An important part of Stretch and
Squash is the idea of weight. That is, in order to make an object
appear as though it has weight there must be an anticipation
and appearance of stress. In Image 2, the first five images
show the jumping man, crouching, bending like a spring in anticipation
of his leap. This kind of movement signals to the viewer that
there is weight that needs to be propelled, and thus the crouching
anticipation called the "Squash".
Likewise, when the motion is stopped,
or the object lands as the figures in Images 2 and 3 both do,
there is a similar squashing as the weight comes to bear against
the surface that stops its motion.
Just as important in Stretch and
Squash is the stretch that occurs between "lift off"
and "land fall." Notice in frames 5 and 6 of Image
2 (lift off) and frames 8 thru 11 of Image 3 (landfall) the
elongation of the figure, or the "Stretch" in anticipation
of the coming action.
Thats basically the idea
behind stretch and squash. An object squashes in anticipation
of propelling itself forward/upward, then stretches in
anticipation of its coming crest, squashes as its
weight shifts from an upward motion to a downward motion, stretches
again in anticipation of landing, and then squashes when
it hits the ground.
and Image 5 show the pawn utilizing the steps listed above.
For this particular animation, Ive added little hic-up
in the middle of the hop where the squash at the crest of the
hop is accentuated to give the character a very rubbery effect,
as though its base it heavier that its top. Notice
also, the added anticipation leaning that occurs at the beginning
of the hop sequence and the rebound after the hop is done. Anticipation
and followthru are always essential to any motion.
Now we have an animation that is
quite a bit better at portraying life. There are definite similarities
and parallels between the Muybridge photographs and the animations
produced. Now there is one more important aspect to making a
One aspect that is often overlooked,
but vital to effective motion is timing. A sure sign of amateur
hopping are "one speed hops;" that is, a hop that
is the same speed when it takes off, as when it crests, as when
it lands. In actuality, an objects speed changes fairly
dramatically over the course of almost all motion; and the hop
is no exception.
When a person jumps (as the two
figures in Images 2 and 3 do), there is an initial burst of
speed as they push off the ground with enough force to cause
them to be airborne. As their "flight" reaches its
crest, their speed slows as their upward momentum tapers off.
When they reach the crest of their jump, their speed in an up-down
direction slows to a near stall, as the momentum begins to shift
downward. The further they have to fall, the faster they move,
until they are moving quite fast when they hit the ground on
the other side of their jump.
shows the pawn making a well-timed hop. Image 6 breaks down
the fast launch, the slowing as it reaches its
peak, its near stop at the crest, and the fast
These are still a multitude of
other character-establishing touches that could be added to
this particular animation. Objects can actually hop will all
sorts of attitudes that express power, diminuitiveness, attitude
and so forth. However, good hops and motion in general is based
upon some important principles that can be learned from real
world examination. Even if the animate object is far from real
world, a viewer will only buy into the motion presented if he
can relate it (even on a subconscious level) to what he knows
These concepts presented here
arent new or revolutionary. Theyve been around
as long as motion animation has been on the screen. From dancing
hippos to running coyotes, the ideas of stretch-squash and
weight are present in all good animation. Watch for it next
time you are viewing a well animated cartoon.