Animation Body Mechanics: Getting Familiar with Ease in and Ease Out
In the previous articles, we covered the Animation Fundamentals, now it's time to get into animation body mechanics. We'll still be covering many of the 12 Principles of Animation but looking at how it applies to bipedal characters, rather than applying the principles to objects like basketballs and pendulums. I feel this is one of the best ways to really understand these principles, by learning how they apply to real-world examples, things that you'll likely be animating on a daily-basis at your workplace or school. Once you get into your first job as an animator, it's unlikely that you'll be tasked with animating a simple ball bounce.
If you're new to animation, I recommend first following along with the Character Animation Fundamentals series before continuing with this article.
In this article, we are going to be talking about ease in and ease out, or slow in and slow out as you may have heard it called before. The important thing is that you understand the principle, and not become stuck on what to call it. They are interchangeable and mean the same thing. You'll also learn how to use ease in and ease out to create a character standing up from a sitting position in the video tutorial at the end of the article.
It may be surprising to you, but you've essentially already applied the principle of ease in and ease out before, in the Animation Fundamentals: Timing and Spacing article. ease in and ease out is in a roundabout way directly associated to the spacing of your animation. In the Timing and Spacing article, you learned how to create a realistic ball bounce utilizing both timing and spacing, but unknowingly you were also learning ease in and ease out.
The same goes for the pendulum animation we did. The reason you can find ease in and ease out in all the animations we finished previously, is because ease in and ease out is found in every single action in the real-world, and has to be incorporated into every single animation in order to create realistic movement. Let's discuss what ease in and ease out really is, and you'll then understand why it's related to your animation's spacing.
Understanding Ease In and Ease Out
As the name suggests, ease in and ease out is essentially the objects slowly getting into a movement, and said object slowing down after that movement. Before anything can move, it has to gain energy, and before something comes to a complete stop that energy needs to slowly dissipate into the final stopping position. A very easy to understand example of ease in and ease out is in a car moving from a complete stop, and the car then coming to a stop after hitting a red light. If you've driven a vehicle before, you know that to go from a stop, to 40MPH takes several seconds, you first have to hit 10MPH and then 20MPH and so on. You don't instantly go from 0MPH to 40MPH in a split second, of course, maybe if you drove a Nissan GTR that may be possible, but not all of us drive race cars.
The same goes for coming to a stop, when you hit a red light, you don't go from 40MPH to 0MPH as soon as you touch the brake. If you did, you would get some serious whiplash. Instead, you gently decelerate, for two reasons, the first is because it's not physically possible to come to a complete stop instantly, the brakes don't work that fast. The second is because it would be extremely uncomfortable if you did. We've all been in the situation where we are in the passenger seat, and the person driving loves to slam on the brakes every time they hit a red light...it's not a very comfortable ride.
In animation, these same real-world principles have to apply, and they don't just apply to vehicle animations. We as human beings essentially move in the same way that a vehicle does. If you go from a standing position to a walk, or even a run you are going to slowly accelerate into the walk. This is the ease in; you're easing into the walk. As you come to a stop, your body doesn't stop all at once, instead, you slowly decelerate into the final standing position. And just like the vehicle example, there are two reasons for this. The first is the fact that we can't just come to a complete stop instantly, our energy first has to dissipate, and we can't just instantly go into a walk, we first have to gain the energy to do so. The second is because, we like to be comfortable, no one likes to stop as fast as they possibly can, and we as human beings like to use the least amount of energy possible.
Even in a sprint, there is still going to be an ease in involved, because it's not physically possible to instantly burst into a run. Now, it's obviously going to be less than the person casually walking around the mall, but it's still there.
So how can all of this relate to spacing? Well, if you think about out it, in order to achieve ease in and ease out in animation you have to adjust the spacing. In order to have an object ease in, you need to make the spacing tighter at the beginning. If you need to have an object come to a stop nice and gently, you need to have the spacing tighter at the end as well. As you can see in the video example above. So you're really already half way there to mastering ease in and ease out! Now you need to understand where to implement ease in and ease out.
While all the examples I've given in the article so far have been an object going from a stop to go, and go to stop. However, this is not the only area where you can find ease in and ease out; it's just the easiest way to understand this principle. You can find ease in and ease out in nearly every single movement that you see. A hand raising to wave, a person turning their head to look at something, even something as small as an eye blink will have ease in and ease out.
This is a principle that can be very subtle, depending on the mood you're trying to set, or very exaggerated. For example, if a person is frightened by a noise, and they look in the direction of the sound, there may be very little ease in, because you want to emphasize that this person is scared, but there may be more of an ease out, as they come to a rest on the final pose. Yes, everything has someease in and ease out, whether it's very subtle, or pronounced, it's up to you to decide what will work best for your particular shot, because ease in and ease out can really help describe what the character is feeling. If you were to add a very large ease in to the same shot where the character is frightened, it wouldn't really have the same feeling, because the movement going on in his body doesn't really fit with the situation.
In a situation like that, is when ease in and ease out can be more difficult to implement. Using ease in and ease out in a scenario where it must be implemented because it's physically correct is easy to spot. A person standing from a sitting position is going to have both an ease in and ease out, because he has to gather his energy. However, finding how you want to implement it into more subtle areas can be more difficult to spot. It really comes down to practice, because you don't want to have a lot of ease in and ease out on every single action a character is taking, because depending on what is happening in the scene it may call for more, or less.
As you can see in the example video above, the red tick marks represent where each keyframe is located, there is ease in, but since he is more surprised, it's not a significant amount, however, on the end pose the ease out is more prominent, as you can see the much tighter spacing at the end. Like most animations, the spacing is more spread out toward the middle of the animation, because that is when the character is at its full momentum.
Creating Your First Animation with Ease In and Ease Out
Step 1: Reference
When you're first starting an animation it's a good idea to find some reference, or shoot some yourself. Even with something as a character standing up from a sitting position it's extremely important that you have some type of reference to base your animation off of. Try to act it out yourself, and pay close attention to the muscles and poses involved to lift yourself up. Where are your hands positioned? How far is your torso leaned forward? Figuring these things out can really speed up the animation process.
Step 2: Blocking
The next step is to begin creating the key poses, for this animation we want it to be as simple as possible. You don't need to have the character placing his hand on the side of the bench, or shifting his weight before standing up. Keep his hands on his thighs, and have him use those to help push his body up. When you're just learning body mechanics you want to keep every shot as simple as possible, focus on the weight, and timing, not how interesting or appealing the animation is. That comes later, when you really nail down how the human body moves.
Step 3: Adding Ease In and Ease Out
Now that you have the key poses of the animation established, it's time to go back through the animation and add the breakdowns. Think about drag, and weight as the character slowly moves his upper body forward. With a standing up animation like this, you want to make sure that his upper body his rotated far enough forward before he ever begins to lift off the chair.
With these breakdowns, you want to begin thinking about ease in and ease out, this is when you really start to create a more realistic animation. A term that is often used when describing how someone implements ease in and ease out is to favor the pose before. So the pose where our character is sitting straight up, and the next key pose where his torso is rotated far forward, to implement ease in you'd want to favor the pose before, which is the pose where his is sitting straight up. This means that instead of creating the breakdown directly in the middle of these two poses, you keep his upper torso rotated further back, closer in line with the pose where he is sitting straight up. This allows the character to ease into the pose where he is rotated all the way forward, just before beginning to stand up.
You'll want to do the same thing for the pose just before he starts to stand up, and the pose where he is halfway through his stand up animation, so his knees should be slightly bent. You'll want to create the pose for the breakdown much closer to the pose where he is still sitting. This makes it so the breakdown is favoring the first pose, easing in to the stand up position.
Step 4: Final Adjustments
With just a few extra poses, you've successfully created the ease in and ease out. Now it's time to go in and add any final tweaks to the animation. Make sure his hands stay planted on his thighs. It's also a good time to adjust the timing if it needs it. Usually when you start to add breakdowns you can get a better idea of the overall timing, and typically, this means something needs to be sped up, or slowed down.
You can see the final animation in the video example, it's nothing exciting, just a character sitting up in the most natural way possible, there is no real character established, because you just want to focus on the body mechanics of the shot. I've also added a motion trail so you can better see the ease in and ease out on the animation.