Frame-by-frame Flash animation: 8-frame basic gait cycle

This is one of the most important learning concepts in animation, and also one of the most technically challenging, as it requires a lot of attention to the movement of opposite limbs.

As difficult as it is, if you master the gait cycle, you can bring just about anything to life. There are many types of gait cycles and you can vary the movement depending on your character or his/her mood; You can do brisk walks, shuffles, random lunges. But the first and simplest is the standard vertical walk, viewed from the side — and that’s what we’re going to tackle in a simplified form below.

  1. About balance bikes
  2. The starting point
  3. Organization of successive frames on the path of movement
  4. leg animation
  5. Foot Animation II
  6. Leg animation III
  7. Motion adjustment to reflect stride length
  8. hand animation
  9. End result

About balance bikes

You can complete a full step cycle in 8 frames, as evidenced by Preston Blair’s gait cycle, one of the most common reference frames in cartoon animations. Many of Preston Blair’s examples are great references and we recommend that you save this image and use it as a reference throughout the tutorial.

The starting point

For your first gait cycle, it is best to try a statue. It’s good practice anyway, because a great way to create animations is to start drawing stick shapes to reduce motion, before building real solid shapes on top of the stick shapes; this can save you a lot of time and a lot of repair work, as it is much easier to define timelines and complex motion issues in form than in detailed form.

Create a scene with a ground line first, because we don’t want our little guy walking in an empty room. Next, create your stick figure (you can either draw it freehand or use the Line and Oval tools; we’ve done a combination of both), referring to the first pose in Preston Blair’s cycle to position his limbs.

To avoid the hassle of redrawing, we’re going to cut off a corner that we couldn’t do if we were doing it by hand using paper, pencils, paint, and squares: we’re going to duplicate the body and head on different frames , so build your little man on several layers. We put our head and body in one layer, our arms in another layer and our legs in a third layer.

A common animation trick is to paint the limbs on the “farthest” side of the body a slightly darker color so that you can distinguish them, especially in cases like these with a simple shape, and so that the shadow makes them disappear in the background. distance.

Organization of successive frames on the path of movement

When you’re done drawing your little man, copy the main frame and paste it into the next seven frames.

You then turn on the onion peel so you can see where your frames are relative to each other, and keyframe the double bodies so they appear to move up and down on the wave, following the motion path shown by the dotted line in Preston’s example – Blair.

The reason for this is that when we – or any creatures for that matter – walk, we don’t exactly move in a straight path. If our legs bend and straighten, and our legs straighten, flatten and push off the ground, we will only go up only to come back down. While walking we never reach the same height as when we are at rest, except for one moment of movement when we pass through this particular space plane.

leg animation

Now we move on to adding limbs to our bodies. One thing that makes the loop loop so difficult is that it is more difficult to select keyframes, especially in the simplified 8-frame loop; almost all frames are keys and you can’t interpolate half the distance between key points. In many ways it is simply a matter of appreciation and familiarity with how the shape moves as you walk.

However, we chose the fourth frame to start with because it’s different enough from our first frame to be a good point of progress, but not so advanced that we can’t look at those two frames in between to see how far each is. limb segment must have been. move between the first and second, as well as the third and fourth.

Using the Preston-Blair demo as a reference, and in our fourth frame (Layer Legs) we drew the legs – with the skate leg almost completely straight and the movable leg slightly raised. We didn’t fully extend the support leg, although some did; it’s just personal preference. However, with exaggerated marches and other flashy gait cycles, strengthening the straight leg can amplify the effect.

Foot Animation II

With these two frames drawn, you should be able to easily add the legs to the second and third frames. In the second frame, the front push leg will begin to bend to accommodate the weight transferred from the hind leg as the hind leg lifts off the ground and the whole body sinks to the lowest point – this means that to maintain balance and keep the frame around the center of gravity, the back bent leg has to bend even more and lower slightly.

Thinking about balance is a good way to judge if your piece looks good in its current moving position; if it looks like he couldn’t hold this position for a second at the momentum displayed on the podium then there might be something wrong with this.

In the third frame, the balance shifts slightly – the front leg stretches out a bit to support more weight, while the back leg begins to lift off the ground and protrude forward. Here you can use the second and fourth frames to help you evaluate this position by looking halfway between the knees, the connection of the upper limbs, the heels of the feet.

One thing to remember is that the knees etc will not be the same height on every frame because the body will tilt up and down and the legs will bend.

Leg animation III

Once you’ve got those first four of the trail you just need to do the next four as the vertical step turns into a slight lunge forward on the next step; use the Preston-Blair link for the fourth and eighth frames, then use your own eyes and reasoning to determine the frames in between. Your end result will look like a depiction of human evolution, but it should show one full step.

One thing to remember about these types of moves is that you should never think clearly. If you see your legs moving, they’re not moving back and forth in vertical paths of motion; they twist at the joints. Almost all movement of a bipedal figure, even if it appears to be vertical, is actually in an arc. Watch the hind leg come up between frame two and three; it doesn’t slide diagonally through the air in a straight line. Instead, it pivots from the hip as the knee follows an invisible arc of motion through the air. Try to bend your leg at the knee and then lift it up from the hip and follow the path of the knee with your eye; this will form a curve rather than a straight line.

You can see this more clearly if you raise your forearm straight in front of your face, palm in and straight; “Chop” the arm to the side without twisting it by moving the forearm at the elbow, and the arc of motion that your fingertips will follow will be easy to follow.

Motion adjustment to reflect stride length

Before we add the arms, let’s make a few adjustments to the placement of each frame. If you clear the timeline and watch the animation, your little guy may slide around a bit and cover too much distance for the one-step cycle depicted. Let’s put everything together so that the movement is accurate.

In one step you only need to cover one stride in the distance. You can measure a simple stride length by drawing a line on a new layer between the heel of the front foot and the heel of the back foot at the point where they are further apart; we have two stride lengths because the stride starts from the center of the stride where the extension is greatest. However, the full eight frames move the figure’s body only one stride length.

The easiest way to align them correctly is to use the legs. During the first four frames, the front leg stays in the same place even as the body moves forward. You can align your heels — and as he begins to bend and lift, align his toes so that although the raised leg moves and the body moves forward, that one fulcrum remains stable.

On the fifth frame, when the moving leg touches the floor while the supporting leg is out of contact, you can switch legs and start aligning the other leg into shape. Basically you should always use your foot on the ground as a guideline to make sure your frames overlap correctly and your shape moves the right distance.

hand animation

Now you have to use the same principles to go back to the weapon layer and fill in those limbs. They work the same way, but the movement isn’t that hard; they don’t bend as much because they don’t meet resistance in the shape of the ground to force the tendon to move and pull. Basically, the arms swing from the shoulders and their position depends on you; we chose what we call “busy arms” or “walking arms” because the constantly flexed arms look like someone in a hurry or accelerating the walker’s speed build-up.

One thing you may notice about the gait cycle is that the arms and legs are always in opposite positions; if the left leg is in front, the left arm is behind. If the right leg is back, the right arm is forward. This also applies to balance and weight distribution; Your body naturally resists your limbs so your weight is constantly flowing evenly to keep you balanced. You can try walking with your arms and legs moving evenly, but you will feel a little uncomfortable and move stiffly — and possibly lean to the side.

End result

Once you’ve completed those eight frames, your animation should look something like this. Of course, it seems a bit strange to stop halfway and pull back – but it’s only one step. However, this is not a complete gait cycle; it’s only half a gait cycle, one step. For a full cycle you need two steps – 15 frames, since your first and last frames will be the same (so “loop” is used), so you don’t need the sixteenth. Your 15th frame will flow right into you to restart the loop, no problem.

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