Ease in, Ease Out – Stop Motion Animation Tutorial

When new animators first start out, most of their big mistakes can be easily fixed with a solid understanding of the 12 Basic Rules of Animation. Though first referenced in The Illusion of Life by Frank Thomas and Ollie Johnson (by the way, new animators, this is a fantastic book), these principles continue to be taught in animation courses around the world.

They’re what makes animation in any medium work.

When you find yourself viewing a botched shot, full of unnatural movement, you can probably trace it back to a failure of one of these twelve rules.

While there is no hierarchy to these rules (in fact, it’s their conglomeration that makes animation work), a fantastic starting point is with “ease in, ease out,” or “slow in, slow out.” Even the most basic motion graphics software will sometimes automatically apply this rule to make sure text doesn’t look strange snapping into place.

The rule goes like this: when starting or stopping an action, you go slow. Begin with a very small movement for at least one or two frames depending on your frame-rate. Even if you are planning a very quick action, you always want to ease in. Let’s take a look at some examples to see how we can apply this in actual animation.

To best illustrate this, let’s meet our actor, the Best Kitten. We’ll call him Bikay.

Bikay likes to whip his tail back and forth, and this motion is a great place to see how “ease in, ease out” looks in practice. Before the larger motion can occur, a very small one needs to be done first. This is quite easy to accomplish when only the tail is moving, but it applies to all motion as well. Every first movement should be small. Even though a frame is only a small fraction of a second, your eye will register that “easing” frame enough so that even a fast whip doesn’t drag with the easing frames. Because this is a loop, there’s only one very small frame at the beginning of the whip, but those are made up for when the loop closes. The small movements on either end of the large action keep the motion from jerking about unnaturally.

In the image below, Bikay’s tail is marked in red to make the spacing easier to see. The numbers correspond to the order of the first 10 frames.

Notice the faster motion gets larger spacing while the slower motion requires more frames bunched closer together. The difference between frames 1 and 2 as well as between 9 and 10 is less than 1mm in real space. It’s that little motion that makes all the difference.

To further illustrate, let’s see what happens when we remove those easing frames.

In this shot, the easing frames from upper left to lower right were removed. The result isn’t horrendous, but there’s a clear difference. The easing frames give it a more natural look, whereas this version jerks about.

So how do you actually achieve this? In 3D computer animation it isn’t particularly hard, but in stopmotion, it can be infuriating when your puppet or your hands won’t cooperate. Here are a few tips.

Build puppets that move the way you want them to

Making armature choices early in the creation process will greatly affect your ability to make small, precise movements. For Bikay, I used 9 gauge aluminum wire on a latex build-up puppet, which is plenty thick to hold it firm. However, if your wire is too thick, you’ll run into inertia problems where a huge amount of force is required to move it at all, and then you find yourself swinging back and forth and never hitting your target movement.

Toggle is your friend

One of the best things I learned for really all of animation, but particularly for these tiny movements is to step back and forth between the previous three or so frames. This is, of course, very tedious, tapping between frames constantly to make sure your movement is what you want. In Dragonframe, there is a toggle button that will automatically bounce between a selected frame and the current live view. However, I find that manually stepping through the frames on the controller works best to make sure you’re moving naturally. As you’re setting up your shot, tap three times quickly on the left arrow, and then three times quickly on the right one. This will often be enough to see if the motion is moving in the right direction and to make sure your arcs* are moving in the right direction.
*If you’re not what I mean by arcs, hold tight. This is another of the 12 basic principles of animation

Practice

Like any other craft, this needs to be practiced. The more you ingrain this rule with regular exercises, the more natural your movements will be. Even for these simple examples, I found myself failing a few times with the easing frames. I’m a bit rusty and so I needed to delete and start over in order to make it move (mostly) the way I wanted.

Let’s look at a longer example with our actor Bikay to see this in a full scale shot instead of just a loop. In the following shot, Bikay is offered a snack, which he promptly pounces on and bops with his paw.

Even in Bikay’s head movement, there is an ease in and ease out frame or two to make sure even those minor movements are rendered naturally. For the pounce itself, the first frame up is a barely perceptible movement before a very large jump. Again, it only takes that tiny movement first to allow for the giant, fast movement to feel natural. Note that a flying rig was used here. I don’t have a magical hovering stop-motion puppet, but rather a thick wire attached to a weight to make sure the puppet could stay suspended. The rig was removed to make it look more real, and because Bikay would rather you believe he can really pounce.

Similarly, look what happens when those easing frames are removed. Bikay still gets to pounce on his goldfish cracker, but action is not convincing. Without easing frames, Bikay doesn’t move the way a real kitten would. Even in this rough example, the easing frames separate a usable shot from a painful retake.

The differences are subtle, sure, but making sure to include easing frames is one of the fastest ways to avoid jerky, unnatural animation. You can practice with full characters or save a lot of time and animate something static like a coin moving from left to right. In real life, no motion starts and stops instantaneously. Gently easing out will make any motion more natural.

Wrapping it up

Remember that animation requires much more than just this one principle (there are twelve after all) and all of them in tandem help create lifelike motion. Now you’ve got somewhere to start, so get practicing!