In this example we have fixed joints

在這個範例內包括了固定關節(Fixed Joint) 和彈簧關節(Spring Joint)

and spring joints.

利用這兩種關節組成這樣的破壞鍊球

This example forms a basic wrecking ball

首先是固定關節 固定關節的原理很像階層裡的父子結構

that does this.

關節會將物件鎖在一個世界座標 或鎖在一個連結的剛體

Firstly the fixed joint. Fixed joints

範例中我們把第一個圓體物件放在天花板 然後加入一個固定關節

work in a similar way to parenting objects

這樣一來它就會被鎖定在該座標

in the hierarchy.

固定關節還可以設定斷裂力道(Break Force) 和斷裂扭力(Break Torque)

The joint simply locks a game object

斷裂力道與斷裂扭力是破壞關節 所需要的最小力量

to the point in the world, or to a

當關節被破壞時 遊戲物件就可以再次自由移動

connected rigidbody.

鍊球其他的圓柱要設定彈簧關節

In this example we simply have placed the

彈簧關節的原理是

first capsule in the chain up near

關節會嘗試移動到目標座標 即物件在場景裡的座標

the ceiling and attached a fixed joint.

而物件的剛體會將關節用一個連在錨點 的隱形彈簧將物件拖離目標位置

This locks it in place.

如果彈簧關節有連結剛體 那它的目標座標

The other parameters of this fixed joint

會指向剛體所屬的遊戲物件 而不是一個世界座標

are Break Force and Break Torque.

舉例來說, 二號圓柱體的目標

This is the minimum amount of force required

是一號圓柱體，而三號圓柱體

to break the joint.

目標是二號圓柱體

When the joint is broken the game object

開始移動時它們不是往原來位置移動 而是往那些圓體物件的錨點移動

can once again move freely.

錨點(Anchor)是關節的支點

The other capsules in the chain have

是彈簧連接遊戲物件的位置

spring joints. Spring joints work on the

錨點在遊戲視圖內以橘色的圓點或方形來表示

principle that the game object is trying

彈性(Spring)參數代表彈簧的韌度 數值越高代表彈簧越緊或堅固

to reach a target position. The target

阻尼(Damper)設定關節動作放慢的速度 數值越高代表彈簧晃過頭的機會越小

position that it's trying to reach is the

最小距離(Min Distance)和最大距離(Max Distance) 設定彈簧活動的一個區域，用來限制彈簧長度

position that it's set to in the scene view

相同於固定關節 彈簧關節也有斷裂力道與斷裂扭力

and any rigid bodies that are attached to it

你可以設定這些力道 來指定斷裂彈簧所需要的最小數值

will pull it away from this position

最後是鉸鏈關節(Hinge Joints)

on an invisible spring attached

鉸鏈關節適合用在門這類的物件

to the anchor point.

鉸鏈關節跟彈簧關節有些參數相似 它的軸向就是旋轉軸向

If the spring joint has a connected rigidbody

在這個範例裡

then the target point that the spring

我們在門加上了鉸鏈關節 然後將錨點設定在X軸的1

is trying to reach is relative to that

代表它的錨點從中心移到了邊緣

game object rather than to world space.

同樣的, Unity的關節是以橘色來表示

So for example, the second capsule here

你可以看到一條橘色的直線 而那就是鉸鏈關節的位置

is trying to reach capsule 1, and capsule 3

這裡的軸向(Axis)代表關節以哪個軸向為支點

is trying to reach capsule 2.

我們將支點設定到Y軸 這樣只要加上簡單的腳本它就會像是真的鉸鏈

As these move they will no longer be heading

腳本裡我們讓門被點擊後 加入往Z軸後推的力量

towards the original positions, rather

往後推的語法是 -transform.forward

they will be heading towards the anchor

在AddForce的教學影片裡的範例 門的物件在加入力量後應該會飛出去

point of wherever those capsules happen to be.

但現在門的物件有了鉸鏈關節

The anchor is the pivot point of the joint.

當我我們對門施加力量 他就會以支點為軸心進行旋轉

You should consider it as where the spring is

所以不管我們對門施加幾次力量 它都不會壞掉

attached to the game object.

就像彈簧關節一樣 我們可以加入一些彈簧的特徵

This is shown in the scene view by

首先將使用彈簧選項(Use Spring)打勾 然後設定彈簧的彈性, 阻尼和目標位置即可

an orange dot or box.

有別於彈簧關節

The spring parameter is a measure of how

鉸鏈關節還有馬達(motor)和限制(limits)設定

strong the spring is. The higher the

馬達設定讓你的關節可以加上速度 就像旋轉門一樣

value the tighter or stronger the

目標速度(Target Velocity)設定關節的旋轉速度

spring becomes. The damper parameter

力道(Force)是要達到目標速度的值

is how much the joint will slow down

假如你勾選了自由選轉(Free Spin) 力道只會用來幫關節加速而不會減速

under motion. The higher the number, the

限制設定是用來限制關節的動態 比如一般的門

less the spring will overshoot.

最小(Min)與最大(Max) 是用來設定關節可以移動的旋轉角度

The min and max distances are for setting

最小回饋(Min Bounce)與最大回饋(Max Bounce)

up a sort of dead zone for where the

用來設定當關節轉到限制角度時所作的反應

spring isn't active. They effectively restrict

跟其他關節一樣 鉸鏈關節也有斷裂力道與斷裂扭力

the length of the spring.

舉例來說, 如果我們在斷裂力道 設定了一個較低的值

Similar to the fixed joint, the spring

當我們在門上施加力量時 就會使鉸鏈關節斷裂

also has a break force and a break torque,

注意到門並非直接向後飛去

which you can set to a certain amount in order

而是從鉸鏈關節點被扯斷

to find the minimum force required to

break that joint.

Finally, Hinge Joints.

Hinge joints are ideal for things like

doors and share some properties with

spring joints. The axis of the hinge

is the one that it rotates around.

In this example our physics door

has the hinge joint attached. The anchor

is set to 1 in the X axis,

which moves it from it's center to it's edge.

Again the joint is represented in

orange in Unity and you can see a small line

showing you where the hinge is currently located.

The axis then allows us to specify

around which axis the hinge will pivot.

We've set this to the Y axis so it will

react like a real hinge with a simple script

we're applying a force to the door

when we click on it, which pushes it

backwards in it's Z axis

using the shortcut minus transform.forward.

In the Add Force lesson you may have seen

that this fires the door straight out of the frame.

But now that we have a hinge,

when we apply the force to the door

it simply pivots around that point.

and no matter how many times we add force

to it, it doesn't break.

In a similar manner to our spring joint

we can apply spring-like characterises

by using the Use Spring checkbox

and using the values underneath the spring settings.

The other differences between hinge joints

and spring joints are motors and limits.

Motors are for introducing a velocity

to your joint, for example a revolving door.

The Target Velocity is the velocity the

joint is trying to rotate at and the

force is used to try and attain that velocity.

If Free Spin is checked then the force will

only be used to try and accelerate

the joint and not to decelerate it.

Limits can be used if you wish to constrain

the motion of your joint, like with the

normal door. The minimum and maximum

are the angles between which the joint

can move. Min and Max Bounce are the amount

by which the joint will bounce when it reaches

one of it's limits. And similar to our

spring joint, yet again we have break

forces and torques.

For example, if we add in a reasonably low

number into the break force property,

we can break the door off of the hinge

when adding a force. You should note that

when doing this the door doesn't fly directly

backwards but is instead pulled away from it's hinge.