So I think I'm going to shift gears here and post something I've been wanting to do since Animation Mentor released it's Animals and Creatures class
(click here for details). I have a couple of projects that I'm working on, but almost finished with. I want to work a funny dialogue animation then I really want to do a quadrupedal animation of some kind of animal. My buddy at work sent me this link and it's really intuitive. It's a bit lengthy, but has some really good stuff in it.
Without further ado, here we go!
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Getting Started
With a media viewer that can scrub single-frame backwards and forwards, like
QuickTime,
you can watch the movement frame by frame. Drawing thumbnail images
with directional notes helps you synthesize the information.
There are now lots of websites out there that put up live-action animal footage, such as the
Rhino House
human and animal locomotion website, which has a built-in player that
can scrub their video reference material (click the image below to check
out their website and viewer). Thanks to the internet, finding
reference and getting into it to see what is going on is the easy part.
The hard part is converting that information into something that makes
sense to the animator and for the character that is to be animated.
Following a process speeds up your workflow. Before I get into the
creative part of animating, I usually have all of my research done.
Gathering and absorbing all of the technical details and reference
material beforehand frees me up to get into the creative flow of
animating, with easy access to my reference material. My process is
something like this:
1. Consider what animal most closely resembles the beast I need to animate.
2. Search for reference material. Here are the sources I find useful:
3. Analyze the reference material and find the section of the footage that is most useful
4. Create thumbnail drawings to assist with my animation,
including notes on direction and any unusual qualities I can see in
footage.
5. Animate
The Four Gaits
In the course of my career, I've learned that there is a surprising
similarity in how quadrupeds move, from species to species. Eadweard
Muybridge's photographic works may be a century old, but they are still
relevant and extremely useful.
In his introduction to Animal Locomotion, he maintains that most
quadrupeds -- be they dogs, cats, horses or rhinoceroses -- follow the
same footfall pattern. This is the order in which the hooves or paws
strike the ground while moving through the various gaits. Where they
differ is in the flexibility of the spine. Visualize a rhino running, as
opposed to a cheetah. The exceptions, according to Muybridge, are
elephants, and animals like kangaroos.
The four speeds of movement, or the four "gaits", are shared amongst
most four-legged animals. Almost every quadruped walks, trots, canters
and gallops, and their legs move in the same manner when they do it.
As you can see in the image below, adapted from Muybridge's Animal
Locomotion, the gaits have been broken down into symbols illustrating
which leg strikes the ground in which order, assuming the animal is
facing north with the right legs on the right and the left legs on the
left.
For example, with the rotary gallop gait, if you start your cycle
with the left rear foot striking the ground first, the next in sequence
to hit the ground would be the right rear foot, then the right fore
foot, followed by the left fore foot.
As for the transverse and rotary gallops, I've found the rotary
gallop more often in reference material than the transverse, which I've
mainly seen in horse footage. The canter is the roughest gait, with a
lot of up-and-down movement. Elephants don't seem to follow these rules,
and should be considered separately.
Once you get the legs moving roughly in the order that is appropriate, you can be creative with the rest of the body.
To save time, you could animate a "vanilla" gait cycle for each gait
with the leg movements blocked in on keys and breakdowns only and the
body and head having the rough up-and-down motion laid in on those keys.
If using a universal rig, this file could then be exported onto any
beast (with minimal adjustments, depending on the disparities of beast
shape) and be used as a starting point for the animations.
Several different types or speeds of walks could also be created from
this base file simply by playing with the amount of frames in the
animation and the distance between the legs in the stride position or
the distance the beast travels in the 'leap' part of the gallop.
The Walk
In the case of the walk gait, the rear left foot strikes first,
followed by the left foreleg. The rear right leg strikes third, with the
right foreleg falling last. The walk is the slowest gait, and is shared
by all quadrupeds. Muybridge breaks down this information into a chart
for the walk, trot, canter and gallop gaits in the introduction of
Animal Locomotion. Converted into a graphic table, a walk cycle would
look like this:
image adapted from: Animal Locomotion, Eadweard Muybridge, 1887
Horses are great animals to study because their legs are so long and
slender, creating an easily legible silhouette. Below is an example of a
walk cycle broken down into 8 phases:
Once you understand what the feet are doing, it becomes easier to
understand what to animate next. Think of the quadruped walk as two
offset human walk cycles. I wonder how often studios have used two
people in a horse costume for motion capture? Preston Blair's iconic
walk cycle with the "stride" and "passing" key positions is a great
illustration of the basics of a biped walk demonstrating the following:
fall into the stride and recover and rise up into the passing position.
Adapted from Preston Blair, Animation, 1948
For the quadruped, the hips and chest become two offset "bouncing
balls" in the same manner as the hips in a bipedal walk. Consider
circled image 23 from the horse walk cycle (below), which shows the
forelegs in the "stride" position and the hind legs in the "passing"
position. I've added circles to show the up and down motion of the hips
and chest in that phase of the movement. The head could then be animated
as yet another bouncing ball, offset from the hips and chest
(follow-through! overlap!)
Animating A Walk
To illustrate this locomotion in 3D animation, I've roughed in a slow
40-frame walk cycle. Cycles must be symmetrical, or there will be a
visible hitch in the walk, like a limp, or a hit in the animation.
There are almost as many methods of animating as there are animators,
but I prefer to approach posing as I would with 2D, or classical,
animation. Posing out the whole character, rather than starting with the
hips or isolating the lower body, and working on the entire character
at once when creating the four major poses.
Details like toes and tails can be ignored or turned off at this
stage. I create the four major keys or poses of the walk: two stride and
two passing. I make them as symmetrical as possible, but they don't
have to be mathematically the same.
There is an advantage to keying all major elements on the same frame.
At this point, the keys can be slid around easily to change the timing
of the walk. It is quick and easy to adapt and manipulate your cycle by
figuring out your basic timing to the point where you start to add
finishing details like overlap and follow-through. Keys arranged in an
orderly fashion are really easy to manipulate in your 3D software
package (here I am using the dope sheet in Maya 2011).
Four key poses, JoJo walk, property of Rocket 5 Studios (Click for larger image)
This is also the break off point where different kinds of walk cycles
can be created now that the feet have been appropriately positioned.
Variety can be added, like floppy overlap or stealthy sneak. The four
basic poses can also be used as a starting point for other walks. You
don't have to recreate the four basic key poses; you only have to adapt
them to your specific purposes. Use the graph editor or tweak by hand,
but remember to have each opposite pose match each other.
JoJo walk cycle, four keys only, with smooth spline interpolation. Watch the animation by clicking here.
It is important that your software has a great graph editor. When
animating cycles, I spend a fair amount of time cleaning up the graph to
get symmetrical movement. Don't forget to check all channels! The above
video has been carefully tweaked to remove all hits and holds. The
stage just prior to this revealed a few errors with the arms:
JoJo with wonky arm movement. Watch the animation by clicking here.
There are several ways to fix errors like this but the easiest for me
at this stage is to look at the graph editor and find out where there
is a problem with the curve.
Note: flat tangents causing slowdown at apex of movement. (Click for larger image)
The highlighted motion trail shows other problems that can be solved
by the graph editor, such as the linear movement of the arm in the air.
Arcs always look more natural than linear paths of action. The solution
for the slowdown in the forward progression of the arm is to fix the
curve so that it can cycle smoothly, as seen below.
Grab spline handles and move them so that curve looks like it can cycle or repeat. (Click for larger image)
The next step is to flesh in the walk, adding overlap and
follow-through, offsetting the head and making sure there is enough
weight in the up and down movements of the hips and chest. When you are
pretty sure the cycle is working the way you want it to, animate the
feet, hands, fingers and toes. I usually animate the tail last, one
rotational axis at a time.
JoJo walk from side view, tail and toes added. Watch the animation by clicking here.
Walks and Runs: In Brief
Walks and runs can be considered a controlled fall with a little
acceleration happening right after the passing position, which is
similar to a push-off. As with all movement cycles, the forward or
Z-translation would be non-linear.
The speed of the walk is dictated by the length of the legs and how
far apart the feet are planted in the stride position. There isn't
really a moment where all four legs are off the ground, as in the other
gaits, and the legs can only move so fast without looking "sped up".
Conversely, the speed of gallop is largely determined by the shape and
unique qualities of the beast. The faster you need the beast to go, the
more flexible the spine will have to be, and the greater the
squash and
stretch.
Look for this when watching reference. As the legs bunch up under the
beast (the squash) energy is gathered, preparing for a "leap" or
"stretch" where the animal can cover as much ground as its form, weight
and strength allow. The tighter the squash, the more extended the
stretch and the faster the beast can travel.
Variety in the weight or "attitude" of the walk, trot, or gallop can
be achieved through the shape and movement in the spine and the amount
of overlap and follow-through. The amount of flexibility and motion in
the spine is key to defining the differences between a horse, a rhino,
and a jungle cat.
Personality, the key ingredient in any good animation, comes not only
from the shape of the key poses but also from what is happening
in between the poses.
How
the character gets from stride to passing can define the character. Are
they high-stepping? Straight forward and no-nonsense? Whimsical? Are
they flopping around like a puppy or are they hard and densely muscled
like a pit bull? The overlapping elements that you've added to the
animation and their follow-through shows the audience who the character
is and what it is made of.
If
your character doesn't have brows (such as the characters in Cars) then
you must use the upper lids to mimic the behavior of brows.
