Norman McLaren, the great 20th century pioneer of animation technique, once said,
20世纪动画技术的先驱者诺曼·麦克拉伦曾说过，
'Animation is not the art of drawings that move, but the art of movements that are drawn.
“动画并不是绘画移动的一门艺术，而是将动态画出来的一门艺术。
What happens between each frame is more important than what exists on each frame.'
与每一帧上的内容相比，帧与帧之间的联系更为重要。”
What did he mean? Well, for an object to appear in motion,
这是什么意思呢？是指要想让物体看起来是在移动的，
it necessarily has to change in position over time.
它的位置必须随着时间的推移而变化。
If time passes and no change in position occurs, the object will appear to be still.
如果时间变化而物体的位置却没有变化，它看起来就是静止的。
This relationship between the passage of time and the amount of change that occurs in that time
时间变化和这段时间中物体位置变化的量之间的关系，
is at the heart of every time-based art form, be it music, dance, or motion pictures.
是每一样以时间概念为基础的艺术形式的核心，比如音乐、舞蹈以及电影艺术。
Manipulating the speed and amount of change between the frames
控制两帧之间物体位置变化的速度和量
is the secret alchemy that gives animation the ability to convey the illusion of life.
是赋予动画生命的秘密法宝。
In animation, there are two fundamental principles we use to do this: timing and spacing.
在动画中，我们遵循两个基本原则来进行这一控制：时间原则和空间原则。
To illustrate the relationship between them, we'll use a timeless example: the bouncing ball.
为了说明这两者之间的关系，我们举一个经典例子：弹跳球。
One way to think about timing is that it's the speed, or tempo, at which an action takes place.
我们可以这样看待时间：时间，是一个动作的速度或者节奏。
We determine the speed of an action by how many pictures, or frames, it takes to happen.
我们增减完成动作所使用的图片，也就是帧的数量，以此决定动作的速度。
The more frames something takes to happen, the more time it spends on screen, so the slower the action will be.
完成动作所使用的帧数越多，它在屏幕上呈现的时间就越长，动作也就越慢。
The fewer frames something takes to happen, the less screen time it takes, which gives us faster action.
反之，完成动作所使用的帧数越少，它在屏幕上呈现的时间就越短，动作就会越快。
The timing is about more than just speed, it's also about rhythm.
时间不仅仅指速度，它也和节奏有关。
Like a drumbeat or melody only exists when a song is being played,
鼓点和旋律只存在于播放的音乐之中，
the timing of an action only exists while it's happening.
同样地，动作的时间只有在动作发生时才存在。
You can describe it in words, say, something will take 6 frames, 18 frames, or so on.
你当然可以用文字来描述它，比如，某个动作需要6帧或者18帧来完成。
But to really get a sense of it, you need to act it out or experience it as it would happen in, well, real time.
但要想真正理解这个动作，你需要在现实时间里再现或体验它。
Now, the timing of an action all depends on the context of the scene and what you're trying to communicate.
也就是说，动作的时间完全取决于背景关联和表达内容。
What is doing the acting, and why? Let's take our example. What makes a ball bounce?
那这些动作是什么？又为什么会有这些动作呢？让我们回到弹跳球的例子，球为什么会弹跳呢？
The action we're talking about here is a result of interacting physical forces,
这实际上是两股力量交互作用的结果：
a moving ball's tendency to stay in motion, or its force of momentum
一方面，运动中的球体由于动力作用想要保持动势；
vs. the constant force of gravity bringing it back down Earth.
而另一方面，地心引力却不断试图将其拉回地面。
The degree to which these invisible forces apply, and the reason why the ball behaves the way it does,
这两方无形力量的作用程度以及球体的运动方式
all depends on the physical properties of the ball.
都是由球的物理特性决定的。
A golf ball is small, hard and light. A rubber ball is small, soft and lighter.
高尔夫球体积小、坚硬、质量轻；橡皮球体积小、柔软、质量更轻；
A beach ball is large, soft and light. And a bowling ball is large, hard and heavy.
沙滩球体积大、柔软、非常轻；而保龄球则体积大、坚硬、非常重。
So, each ball behaves very differently, according to its properties.
所以，每种球都会因其特性而有不同的表现。
Let's get a sense of the visual rhythm of each.
让我们感受一下每种球运动的视觉节奏。
Each ball plays its own beat and tells us something about itself and the time it takes to travel across the screen.
每种球都有自己的节拍，以此来告知我们其特性以及它们穿过屏幕所需的时间。

The visual rhythm of these hits is the timing.
球体连续撞击地面所产生的视觉节奏体就是时间。
Okay, let's start animating our ball, bouncing up and down with a simple cycle of drawings.
现在，让我们用简单的绘画让这个球跳动起来。
We'll draw a circle here, call it point A, our starting point.
在这里画一个圆圈，作为点A，是运动的起始点。
We'll have it hit the ground here, point B.
我们让球体在这里接触地面，也就是点B。
Let's say it takes about a second to hit the ground and come back up again. This is our timing.
假设球体从点A落下触地再弹回需要一秒钟。这就是我们所说的时间。
Our spacing is where we position the circle in the frames between point A and point B.
而空间则是指每一帧里点A和点B的位置关系。
If we were to move our ball in evenly-spaced increments, we'd get something like this.
如果我们让球体按等距离运动，就会得到这样的效果。
It's not really telling us anything about itself.
我们很难以此判断这究竟是什么。
Is it a bouncing ball or a circle on an elevator?
是一个弹跳球？还是电梯上的一个圆圈？
Let's look at our footage again and think about what's going on as each ball bounces.
让我们再来看一下球弹跳的画面，并且思考每种球到底是如何弹跳的。
Following each impact with the ground, the ball's upward momentum is eventually overcome by gravity.
在球体与地面接触后，其向上的动势最终被地心引力消除。
This happens at the peak of each arc. As things change direction, the motion is slowest.
此时球体达到弧线轨迹的顶点。球体改变方向的那一刻，其运动速度最慢。
We see here the successive positions of the ball are close together.
在顶点附近，球的连续位置非常紧密。
The ball then speeds up as it falls, and is at its fastest when it's approaching and hitting the ground.
此后球体下落，速度加快，在它即将接触地面的瞬间，速度达到峰值。
We can see here each position is further apart.
远离顶点，球的连续位置则较为松散。
The change in position between frames is the spacing.
帧与帧之间物体位置的变化体现出空间原则。
The smaller the change, the slower the action will appear.
位置变化越小，动作显得越慢。
The greater the change, the faster it will appear.
位置变化越大，动作则显得越快。
For an action to decelerate, each change in position must be less than the change before it.
动作由快变慢，位置变化必须逐渐减小。
Likewise, for an action to speed up, or accelerate, each successive change must be greater.
同样地，动作由慢变快，位置变化则要逐渐增大。
Let's change the mechanical spacing of our animated bounce to reflect what we observed in the footage.
让我们通过调节球体的位置变化来表现此前在影片中所看到的球体运动。
Slow at the top, fast when it's hitting the ground.
到达顶端时速度放缓，落向地面时速度加快，
Simply by adjusting the spacing,
仅仅通过调整空间关系，
we've succeeded in suggesting the forces of momentum and gravity at play and achieved a much more realistic motion.
我们成功地反映了动力与地心引力的作用，并更为真实地表现了球体的运动。
Same timing but different spacing gives us vastly different results.
运动时间相同，但空间变化不同，所产生的效果也大不相同。
And in reality, as a ball bounces, the physics of gravity eventually defeat the tendency of the ball to stay in motion.
现实中的情况是，地心引力终将完全消除球的动势。
You can see this here in the decreasing height of each successive bounce.
从球越跳越低的趋势中你就能看出这一点。
However, again, this decrease varies according to the properties of the ball.
但仍要强调，根据球特性不同，这种趋势也有不同的表现。
Even though these circles are the same size here,
虽然这两个圆圈大小相同，
they're each telling us a different story about themselves, purely in how they move.
但仅仅通过不同的运动方式，它们就能展现各自不同的特性。
The relationship between these principles of timing and spacing
这些时间和空间原则之间的关系能以无数种方式被运用，
can be applied in countless ways and used to animate all types of action:
并可以用来为任何动作制作动画：
a yo-yo, a punch, a gentle tap, a push, a saw, the Sun traveling across the sky, a pendulum.
悠悠球，击打动作，轻轻地敲击，推的动作，锯子的运动，日升日落，钟摆运动。
Animation is a time-based art form.
动画以时间概念为基础的艺术形式。
It may incorporate the aesthetic elements of other graphic arts, like illustration or painting,
它虽包含插画、油画等绘画艺术的审美元素，
but what sets animation apart is that, here, what you see is less important that what you don't see.
却也有其独特之处，那就是，你在画面上没有看到的东西要比你所看到的更为重要。
An object's superficial appearance only tells us so much about itself.
物体的表象能告诉我们的东西有限。
It's only when it's in motion that we really understand its nature.
只有当它们运动起来，我们才能真正理解其本质特性。