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第一篇，就写个物理车的！
首先，资料的来源!http://www.gotow.net/andrew/wordpress/?page_id=78在这个链接的底部有下载的链接，如果下载不 到， 我可以共享出来！
第二部，开始一些翻译和讲解！
1.物理车的碰撞！
其中草绿色线条是车的两个包围盒！四个轮子加了四个车轮碰撞器(WheelCollider);
2.物理车的层次结构关系
根节点是PlayerCar,Colliders,就是第一张图中的两个包围盒
WheelColliders的子物体就是四个车轮碰撞器！
Wheels的子物体就是四个车轮！
第三部份，代码注解：
代码使用JS写的！
首先是：PlayerCar_Script.js
View Code
1 // ----------- CAR TUTORIAL SAMPLE PROJECT, ? Andrew Gotow 2009 -----------------
2
3 // Here's the basic car script described in my tutorial at www.gotow.net/andrew/blog.
4 // A Complete explaination of how this script works can be found at the link above, along
5 // with detailed instructions on how to write one of your own, and tips on what values to
6 // assign to the script variables for it to work well for your application.
7
8 // Contact me at Maxwelldoggums@Gmail.com for more information.
9 //这些是外国人写的赛车例子，我个人认为非常好，是用JS写的！
10 //我来注解一下！
11 // These variables allow the script to power the wheels of the car.
12 //前左轮和前右轮
13 var FrontLeftWheel : WheelCollider;
14 var FrontRightWheel : WheelCollider;
15 // These variables are for the gears, the array is the list of ratios. The script
16 // uses the defined gear ratios to determine how much torque to apply to the wheels.
17 //齿轮转数系数
18 var GearRatio : float[];
19 //档位
20 var CurrentGear : int = 0;
21 // These variables are just for applying torque to the wheels and shifting gears.
22 // using the defined Max and Min Engine RPM, the script can determine what gear the
23 // car needs to be in.
24 //向前的动力
25 var EngineTorque : float = 600.0;
26 //引擎最大的转速
27 var MaxEngineRPM : float = 3000.0;
28 //引擎最小的转速
29 var MinEngineRPM : float = 1000.0;
30 private var EngineRPM : float = 0.0;
31 function Start () {
32 // I usually alter the center of mass to make the car more stable. I'ts less likely to flip this way.
33 //设置车的中心点，一般在车的底盘下，这样车行驶起来稳定，不会轻易翻车！
34 rigidbody.centerOfMass.y = -1.5;
35 }
36 function Update () {
37 // This is to limith the maximum speed of the car, adjusting the drag probably isn't the best way of doing it,
38 // but it's easy, and it doesn't interfere with the physics processing.
39 //设置车的阻力为 车的向前的速度的长度除以250
40 rigidbody.drag = rigidbody.velocity.magnitude / 250;
41 // Compute the engine RPM based on the average RPM of the two wheels, then call the shift gear function
42 //档位的转速值车
43 EngineRPM = (FrontLeftWheel.rpm + FrontRightWheel.rpm)/2 * GearRatio[CurrentGear];
44 ShiftGears();
45 // set the audio pitch to the percentage of RPM to the maximum RPM plus one, this makes the sound play
46 // up to twice it's pitch, where it will suddenly drop when it switches gears.
47 //音频源的音调 发动机的引擎转速越快，则音调越高！
48 audio.pitch = Mathf.Abs(EngineRPM / MaxEngineRPM) + 1.0 ;
49 // this line is just to ensure that the pitch does not reach a value higher than is desired.
50 //超过2.0则归位到2.0
51 if ( audio.pitch > 2.0 ) {
52 audio.pitch = 2.0;
53 }
54 // finally, apply the values to the wheels. The torque applied is divided by the current gear, and
55 // multiplied by the user input variable.
56 //前面的两个轮子的力矩
57 FrontLeftWheel.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
58 FrontRightWheel.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
59 Debug.Log(Input.GetAxis("Vertical"));
60 // the steer angle is an arbitrary value multiplied by the user input.
61 FrontLeftWheel.steerAngle = 10 * Input.GetAxis("Horizontal");
62 FrontRightWheel.steerAngle = 10 * Input.GetAxis("Horizontal");
63 }
64 //换档位
65 function ShiftGears() {
66 // this funciton shifts the gears of the vehcile, it loops through all the gears, checking which will make
67 // the engine RPM fall within the desired range. The gear is then set to this "appropriate" value.
68 //如果当前引擎的值大于最大引擎
69 if ( EngineRPM >= MaxEngineRPM ) {
70 var AppropriateGear : int = CurrentGear;
71 //则从0开始，往上查，如果左轮的rpm乘以齿轮数小于
72 for ( var i = 0; i < GearRatio.length; i ++ ) {
73 if ( FrontLeftWheel.rpm * GearRatio[i] < MaxEngineRPM ) {
74 AppropriateGear = i;
75 break;
76 }
77 }
78
79 CurrentGear = AppropriateGear;
80 }
81
82 if ( EngineRPM <= MinEngineRPM ) {
83 AppropriateGear = CurrentGear;
84
85 for ( var j = GearRatio.length-1; j >= 0; j -- ) {
86 if ( FrontLeftWheel.rpm * GearRatio[j] > MinEngineRPM ) {
87 AppropriateGear = j;
88 break;
89 }
90 }
91
92 CurrentGear = AppropriateGear;
93 }
94 }
解释：
FrontLeftWheel.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
FrontRightWheel.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
设置车轮的motorTorque可以使车轮滚动！
FrontLeftWheel.steerAngle = 10 * Input.GetAxis("Horizontal");
FrontRightWheel.steerAngle = 10 * Input.GetAxis("Horizontal");
设置车轮的steerAngle可以控制车轮围绕自身Y轴的转向角度！这里的旋转角度是-10度到10度之间！
作者疑问：
第57,58,60,61行代码，
FrontLeftWheel.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
Input.GetAxis("Vertical")会返回-1，也就是说motorTorque是负值！
但是官方文档却说，
在轮轴上的电机力矩。根据方向正或负。
To simulate brakes, do not use negative motor torque - use brakeTorque instead.
模拟刹车，不要使用电机力矩负值，使用brakeTorque代替。
这两种说法之间可有冲突，请高手指点！
下篇是车轮与其他物体的碰撞，待续……！