I'm a software engineer at Pixar.

我是皮克斯的軟體工程師。

I worked on the hair simulator

我為電影勇敢傳說製作頭髮模擬器。

for the movie, Brave.

Hair was a really big deal in Brave.

在勇敢傳說裡，頭髮是件大事。

It was a symbol of freedom that was intrinsic

它是我們主角梅莉達真正的性格中。

to our main character Merida's personality.

自由的象徵。

And making hair that feels right,

而讓頭髮做得很對味，

meaning messy, wild and free,

意味著凌亂，狂野和自由，

is a hard thing to do computationally.

這在技術上是很難的。

In our movies, hair is a simulated effect.

在電影中，頭髮是一種模擬出來的效果。

That means no one animates its movement by hand.

這意味著沒有人動手把頭髮繪製出來。

The way it moves is defined by physics

頭髮的動向是由物理定義。

and programmed into the computer.

然後用電腦編成出來的。

To figure out what hair simulation should look like,

為了弄清楚頭髮的樣子，

we needed to look at real curly hair

我們得看真正的捲髮如何運作的。

and see how it worked.

What we found was this.

我們發現了這個。

Curly hair forms together in locks

捲髮捲在一起形成結，

that reshape themselves when you pull on them,

當你拉它們時，他們會重塑，

kind of like a spring.

有點像彈簧。

This was great news because springs

這是個好消息，因為彈簧，

can be modeled mathematically,

可以以數學公式去做程式。

meaning we can simulate their behavior

這意味著我們可以用電腦程式模擬它的行為。

using a computer program.

From the computer's perspective,

從電腦技術的觀點來看，

Merida's hair is just lots and lots of springs

梅莉達的頭髮有很多線條。

that react to forces, such as gravity,

會隨著他的動作對力量像是引力去做反應。

as Merida moves.

The tests we ran using this approach were pretty good,

我們使用這種方法實行的測試效果非常好，

but not quite natural enough.

但不夠自然。

While stiffer springs held the shape of the curl,

雖然較硬的彈簧保持捲曲的形狀，

it didn't bounce like natural curls.

但它看起來不向自然的捲髮。

When we made the springs loser,

當我們讓彈簧更鬆些，

her curls would unwind when she moved.

在她動的時候，她的捲髮會變得鬆垮些。

This was even more obvious at high,

在動畫中的高速移動或較不真實的的速度下，

often unrealistic speeds, found in animation.

這一點更為明顯。

We realized we needed something

我們發覺我們需要一些東西去，

to preserve the structure of the curl,

保持捲髮的結構，

but not impede the overall motion of the hair,

同時不會阻礙整個頭髮的動向。

kinda like digital hairspray.

我們需要個數位髮膠。

(can hissing) Oh, sorry (laughs).

(髮膠噴出聲) 抱歉 (笑)。

We came up with the idea of connecting

我們提出了將她的頭髮彈簧連接到。

the springs that make up Merida's on-screen hair

像這樣的隱形核心。

to invisible core springs like this.

The core springs would limit the movement

彈簧中的隱形核心會在劇烈運動時限制頭髮的動向。

of the on-screen hair

when the motion was more extreme.

This way, we could have the best of both worlds.

這樣的話，我們可以達成我們要的效果。

Our original simulation we create motion

我們的原始模擬運動。

that was soft and natural,

是很柔軟自然的，

but the core springs would keep the curl

但核心彈簧可以防止捲曲，

from unwinding too much.

過度展開。

Figuring out how to make a hair simulation system

弄清楚如何使頭髮模擬系統，

that could help us achieve the feeling we wanted

幫助我們實現我們想要的梅莉達頭髮的感覺。

for Merida's hair was hard.

是件很困難的事。

It took a lot of iterations to get it right,

經過大量的重作，我們才能做到最對味的效果，

but it made a big difference.

但它產生了很大的不同。

Merida feels like a real girl,

梅莉達看起來像是個真實的女孩，

messy, wild and free.

麻煩、狂野且自由的。