Animation basics: The optical illusion of motion - TED-Ed

翻译人员: Gabriella Hu 校对人员: Jenny Yang

有一串静态的，连续的图画

Take a series of still, sequential images.

Let's look at them one by one.

我们一张一张地看

Faster.

加快

现在我们把间隔去掉，

Now, let's remove the gaps,

go faster still.

加快

Wait for it ...

等等...

Bam!

瞧！

Motion!

动态图像！

Why is that?

为什么会这样呢？

Intellectually, we know we're just looking at a series of still images,

其实，我们知道我们只是在看

一系列的静止图片，

but when we see them change fast enough,

但是当它们更换地足够快时，

they produce the optical illusion of appearing as a single, persistent image

它们产生一种错视

貌似只有一张图片上有

渐渐变化着的形状和姿势

that's gradually changing form and position.

这中效果是动画技术的基础，

This effect is the basis for all motion picture technology,

from our LED screens of today

从如今使用的发光二极管屏幕

to their 20th-century cathode ray forebearers,

到它的“祖先”：20世纪阴极射线，

从电影胶片放映

from cinematic film projection to the novelty toy,

到一种新奇玩具，

甚至，有人提出，

even, it's been suggested, all the way back to the Stone Age

一直追溯到石器时代

从人类开始在洞壁上画图开始

when humans began painting on cave walls.

This phenomenon of perceiving apparent motion in successive images

这种在连续的图片中感觉到动感的

奇特现象

is due to a characteristic of human perception

是因为人们的感知能力的特点

historically referred to as "persistence of vision."

在历史上被称为 “视觉暂留”

The term is attributed

这个术语归因于

to the English-Swiss physicist Peter Mark Roget,

英裔瑞士物理学家彼得·马克·罗杰特，

who, in the early 19th century,

在19世纪早期，

used it to describe a particular defect of the eye

用这个术语描述眼睛的一种缺陷

that resulted in a moving object

造成当一个移动的物体

达到一定的速度时，它看上去像静止的

appearing to be still when it reached a certain speed.

Not long after, the term was applied to describe the opposite,

此后不久，

这个术语被用来描述恰恰相反的现象：

the apparent motion of still images,

静止的图像看似在运动，

by Belgian physicist Joseph Plateau, inventor of the phenakistoscope.

比利时物理学家约瑟夫·普拉托，

费纳奇镜的发明者运用了这个术语

他把“视觉暂留“定义为

He defined persistence of vision as the result of successive afterimages,

连续的残像

which were retained and then combined in the retina,

在视网膜中被保留并合并，

使我们认为我们所看到的

making us believe that what we were seeing is a single object in motion.

是一个动态物体

This explanation was widely accepted in the decades to follow

这个解释在接下来的几十年中

被广泛接受

and up through the turn of the 20th century,

一直到十九和二十世纪之交，

有些人开始质疑

when some began to question what was physiologically going on.

从生理学角度这到底是什么现象

In 1912, German psychologist Max Wertheimer

1912年，德国心理学家马克思·韦特海默

outlined the basic primary stages of apparent motion

他用简单的错视概述了看似运动的物体

的基本的阶段

using simple optical illusions.

These experiments led him to conclude

这些实验使他断定

这一现象是因为视网膜后面的

the phenomenon was due to processes which lie behind the retina.

一系列过程

In 1915, Hugo Münsterberg,

在1915年，雨果·芒斯特伯格，

a German-American pioneer in applied psychology,

一名应用心理学先驱的德裔美国人

也提议连续的图像

also suggested that the apparent motion of successive images

表面上的运动

is not due to their being retained in the eye,

并不是因为图像被保留在眼睛中，

but is superadded by the action of the mind.

而是大脑促成的

In the century to follow, experiments by physiologists

在接下来的一个世纪中，

生理学家的多次实验

也证实了他们的结论

have pretty much confirmed their conclusions.

As it relates to the illusion of motion pictures,

这与动态图画的错觉有关，

persistence of vision has less to do with vision itself

所以视觉暂留和视觉本身没有很多关联

than how it's interpreted in the brain.

而是大脑是如何分析图像的

Research has shown that different aspects of what the eye sees,

研究表明眼睛从不同角度

所观察到的物体，

like form, color, depth, and motion,

比如形状，

颜色，

深度，

和动感，

are transmitted to different areas of the visual cortex

被传输到视觉皮层的不同部位

via different pathways from the retina.

通过视网膜中不同的途径

It's the continuous interaction

视觉皮层中不同的部位的

of various computations in the visual cortex

不同的感应之间持续互动

that stitch those different aspects together

使这些不同角度看到的东西结合在一起

促成了视觉的感受

and culminate in the perception.

Our brains are constantly working,

我们的大脑在不断地工作，

synchronizing what we see, hear, smell, and touch

同步我们所看到的，

听到的，

闻到的，

into meaningful experience

和触摸到的，

把流动的瞬间结合成

有意义的体验，

in the moment-to-moment flow of the present.

So, in order to create the illusion of motion in successive images,

为了创造连续性图像的

动感的错觉，

we need to get the timing of our intervals

我们需要使间隔时间

close to the speed at which our brains process the present.

接近我们大脑领会现状的速度

So, how fast is the present happening according to our brains?

我们的大脑识别现状的速度到底有多快呢？

Well, we can get an idea

我们可以通过

测量图片需要以多快的速度切换

by measuring how fast the images need to be changing

才会有动感的效果

for the illusion to work.

Let's see if we can figure it out by repeating our experiment.

让我们重复我们的实验，

解开这个难题

Here's the sequence presented at a rate of one frame per two seconds

这一系列图片

是以每两秒种一个图片的速度

再加上一秒钟的间隔

with one second of black in between.

At this rate of change,

以这个速度，

with the blank space separating the images,

还有图像之间的间隔，

there's no real motion perceptible.

我们无法感觉到动感

As we lessen the duration of blank space,

当我们渐渐减少间隔时间时，

a slight change in position becomes more apparent,

图片中人物的位置的变化更加明显了，

然后你开始慢慢感觉到在图像中

and you start to get an inkling of a sense of motion

有动态效果了

between the disparate frames.

每一秒钟一个图像，

One frame per second.

Two frames per second.

每秒两个图像，

Four frames per second.

每秒四个图像

Now we're starting to get a feeling of motion,

现在我们有动态的感觉了，

but it's really not very smooth.

但是不是非常流畅

We're still aware of the fact that we're looking at separate images.

我们还能意识到

我们在看独立的图像

Let's speed up. Eight frames per second.

让我们加速，

每秒8个图像，

每秒12个图像

12 frames per second.

It looks like we're about there.

看上去差不多了

At 24 frames per second, the motion looks even smoother.

以每秒24个图像的速度，

感觉更加流畅了

This is standard full speed.

这是标准的全速

So, the point at which we lose awareness of the intervals

当我们意识不到间隔，

and begin to see apparent motion

并且开始感觉到动感时，

图像速度大约在每秒8-12个图像

seems to kick in at around eight to 12 frames per second.

这个速度就是

This is in the neighborhood of what science has determined

用科学测量出的

我们观察独立的图像的意识

to be the general threshold of our awareness

的速度

of seeing separate images.

一般来说，当我们失去那种意识时

Generally speaking, we being to lose that awareness

速度大约是每张图像100毫秒，

at intervals of around 100 milliseconds per image,

约等于每秒10个图像的

which is equal to a frame rate of around ten frames per second.

帧速率

As the frame rate increases,

帧速率增加时，

we lose awareness of the intervals completely

我们就彻底失去了图片之间有间隔的意识，

and are all the more convinced of the reality of the illusion.

也就更加确信

了幻觉的真实性