Flash Frame-By-Frame Animation: 8-Frame Basic Walk Cycle

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About Walk Cycles

Preston Blair Walk Cycle.

The is one of the most important learning concepts in animation--and also one of the most technically difficult because it requires so much attention to the movement of opposing limbs.

However difficult, though, if you can learn to master a walk cycle then you can animate just about anything. There are many types of walk cycles, and you can vary the motion to match your character or his/her mood; you can do bouncy walks, shuffling walks, casual slouches. But the first and simplest is the standard upright walk, viewed from the side--and that's what we're going to attack in simplified form today.

You can cover the cycle of a full stride in 8 frames, as demonstrated by the above walk cycle: the Preston Blair walk cycle, one of the most common reference images in cartoon animation. Many Preston Blair examples are great learning references, and I'd advise you to save that image and use it as a reference throughout the entire lesson.

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Starting Point

For your first walk cycle, it's best to try a stick figure. It's good practice, anyway, as a great way to build your animations is to start by drawing stick figures to get the motion down before building actual solid shapes on top of those stick figures; it can save you a lot of time, and a lot of correction work, as it's much easier to work out timelines and difficult motion issues in stick figures than in detailed forms.

To start off, set up a scene with a ground line, as we don't want our stickman walking in empty space. Then build your stick figure (you can draw it freehand or use the Line and Oval tools; I did a combination of both), referencing the first pose in the Preston Blair cycle to position his limbs.

To save some trouble redrawing things, we're going to cut a corner that we couldn't do if we were doing this by hand using paper, pencils, paint, and cels: we're going to duplicate the body and head across different frames, so build your stick-man on different layers. I put my head and body on one layer, my arms on another layer, and my legs on a third layer.

A common trick in animation is to make the limbs on the "far" side of the body a slightly darker color so that you can distinguish between them, especially in cases such as this with a simple shape, and so that the shadow makes them seem to recede into the distance.

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Arranging Sequential Frames in a Path of Motion

Once you've finished drawing your stick-man, copy the keyframe for the body/head and paste it across the next seven frames.

Then you're going to turn on onion-skinning, so that you can see where your frames are in reference to each other, and space out your duplicate bodies across the keyframes so that they seem to move in an up-and-down wave, following the path of motion demonstrated by the dotted line in the Preston-Blair example.

The reason for this is because when we--or any creatures--walk, we don't travel exactly in a straight path. As our legs bend and straighten, and our feet extend, flatten, and push off from the ground, we're going to be propelled upwards only to sink down again. When walking we're never the exact same height as we might be in a resting position, save for in a single instant of motion as we pass through that particular plane of space.

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Animating the Legs

Now we're going to move on to start adding limbs to our bodies. One thing that makes a walk cycle so difficult is that it's harder to pick keyframes, especially in a simplified 8-frame cycle; almost all of the frames are keys, and you can't interpolate half-distances between key points. A lot of it is just a matter of estimation and familiarity with the way the form moves in a walk.

I picked my fourth frame to start with, however, because it's different enough from my first frame to be a good point of progress, but not so advanced that I can't eyeball the two in between to estimate just how far each segment of limb should have moved between first and second, and third and fourth.

Using the Preston-Blair demonstration as a reference, and on my fourth frame (Legs layer) I drew my legs--with the supporting leg almost fully straight, and the traveling leg slightly upraised. I didn't completely straighten the supporting leg, although some choose to; this is just a personal preference, as I don't know about you but I can't completely thrust my leg out in a straight piston while walking without locking my knees rather painfully. For exaggerated marches and other flamboyant walk cycles, however, emphasizing a straightened leg can add to the effect.

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Animating the Legs II

With those two frames drawn, you should be able to add the legs to your second and third frames easily enough. The second frame is where the forward-thrust leg begins to bend to catch weight transferred from the back leg as the back leg pushes off of the ground, and the entire body dips to its lowest point--which means that in order to keep balance and keep the frame stable around its center of gravity, the backwards-bending leg has to bend more and come a bit further down, as well.

Thinking of balance is a good way to judge by eye whether your figure looks right in its current frame of motion; if it looks like it couldn't possibly hold that position for a second at the momentum depicted in the scene, then there's probably something a bit wrong with it.

In the third frame, the balance shifts a bit--the forward leg straightening a bit more and thus capable of supporting more weight, while the backward leg begins to lift off the ground and come forward. Here you can use the second and fourth frames to help you estimate that position, by looking at halfway points between the knees, the joining of the upper legs, the heels of the feet.

One thing you'll want to remember is that the knees, etc. won't be at the same elevation for each frame, because the body is dipping up and down and the legs are bending.

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Animating the Legs III

If you've got those first four out of the way, you should be just fine doing the next four as the upright step turns into a mild forward lunge into the next step; use the Preston-Blair reference for the fourth and eighth frames, and then use your own eyes and reasoning to work out the frames in between. Your end result will come out looking like a depiction of the evolution of man, but it should portray a single full step.

One thing you need to remember about this sort of motion is that you should never really be thinking in straight lines. If you observe the way the legs move, they don't scissor back and forth on vertical paths of motion; they rotate at the joints. Almost all motion of a bipedal figure, even if it looks vertical, is actually taking place on an arc. Watch as the back leg lifts between frames two and three; it doesn't glide through the air diagonally in a straight line. Instead, it pivots from the hip, while the knee traces an invisible arc of motion in the air. Try bending your leg at the knee and then lifting it up from the hip, and trace the path of motion of your knee with your eye; it will form a curve, rather than a straight line.

You can see it more clearly if you raise your forearm straight before your face, with your hand palm inwards and flat; "chop" your hand to the side without twisting it, moving your forearm at the elbow, and the arc of motion that your fingertips trace will be easy to follow.

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Adjusting Motion to Reflect Stride Length

Before we add the arms, let's make a few adjustments to the positioning of each frame. If you scrub your timeline and watch your animation, your stick-man may appear to glide a little bit, covering too much distance for the single step cycle depicted. Let's pull everything together so that the motion is accurate.

For a single step, you should only cover one stride length in distance. You can take a simple measure of stride length by drawing a line on a new layer between the heel of the forward foot and the heel of the backwards foot at the point where they're the farthest apart; I have two stride lengths depicted, because the step starts off mid-stride where the extension is the greatest. The full eight frames, however, only move the figure's body over one stride length.

The easiest way to line them up properly is to use the feet. For the first four frames, even as the body travels forward, the forward foot remains planted in the same spot. You can line the heels up--and, as it starts to bend and lift, line the toes up so that although the upraised leg travels and the body moves forward, that single support point remains stable.

On the fifth frame, when the moving leg touches the ground while the base leg leaves contact, you can switch feet and start lining up opposite foot on your shape. Basically, you should always use the foot that's on the ground as your point of reference to make sure your frames overlap properly and your figure travels the correct distance.

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Animating the Arms

Now you should use the same principles to go back to your Arms layer and start filling in those limbs. They work the same way, but the motion isn't quite so complex; they don't bend as much because they're not meeting resistance in the form of the ground to cause sinew to shift and pull. Mostly the arms swing from the shoulders, and the position of them is up to you; I chose what I call "busy arms" or "walkers' arms" because the constantly-bent arms look like someone in a hurry or else a speed walker building momentum.

One thing you may notice in a walk cycle is that the arms and legs are always in opposing positions; if the left leg is forward, the left arm is back. If the right leg is back, the right arm is forward. This, too, relates to balance and distribution of weight; your body naturally counter-swings your limbs so that your weight is constantly flowing evenly to keep you on balance. You can try walking with your arms and legs moving in even synchronicity, but you'd be a bit uncomfortable and find yourself moving rigidly--and possibly leaning to one side.

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Finished Result

When you finish those eight frames, your animation should look similar to this. Of course, it seems a little odd, stopping mid-stride and jerking back--but that, right there, is a single step. It is not, however, a full walk cycle; it's only half of a walk cycle, a single step. In order for a full cycle, you need two steps--fifteen frames, as your first and last frames, will be the same (thus the use of "cycle") and so you won't need a sixteenth. Your fifteenth frame would flow right into you're first to begin the cycle anew, seamlessly.