Unity实现Angry Bird弹弓发射功能

首先声明，Unity版本为5.4.4

这篇主要是针对Unity官网上的一个视频教程，功能就是实现一下Angry Bird中弹弓发射的功能

先去Asset Store上下载2D Sprites Pack素材包，导入到Unity中

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下面开始搭建场景：

1.将相机设为正交投影

2.在导入的素材中找到背景并拖到Hierarchy中改名为BackGround

3.在素材中找到地面拖到Hierarchy中并改名为Grass

4.新建一个空物体改名为Ground，多复制几个Grass并在Scene下摆放到适当的位置，调整背景的长度

5.给Ground添加Edge Collider2D并点击Edit Collider调整点的位置使线平行地面且端点位于背景左右

6.在素材中找到弹弓(是俩张图，把1作为0的子物体)拖到Hierarchy上并改名

7.在素材中找到投射物并拖到Hierarchy上改名为Asteroid

8.在Scene视图中摆放合适位置

9.设置Sorting Layer,随便点击场景中的图片，在Sorting Layer上点击Add Sorting Layer，新建ForeGround

10.BackGround设置为Default层，所有的Grass设置为ForeGround层order in layer为0，CatapultSprite设置为ForeGround层，order in layer为0，CatapultSprite_1设置为ForeGround层，order in layer为4，Asteroid设置为ForeGround层，order in layer为2

11.在素材中找到木板拖到场景中，并复制多个，怎么摆放都行,并且添加Box Collider2D和Rigidbody2D

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下面开始实现功能

1.给Asteroid添加Circle Collider2D和Rigidbody2D，新建一个 Physics2D Material改名为HighFriction

2.新建一个Material命名为Band

3.给CatapultSprite添加Rigidbody2D并勾选Is Kinematic,分别给CatapultSprite和CatapultSprite_1添加Line Renderer,把Band分别拖到Line Renderer的Materials上

4.给Asteroid添加Spring Joint2D,把CatapultSprite拖拽到Spring Joint2D上的Connected Rigid Body上

新建C#脚本ProjectileDragging并拖到Asteroid上

using UnityEngine;using System.Collections;public class ProjectileDragging : MonoBehaviour {    public float maxStretch = 3.0f;//拉伸长度    public LineRenderer catapultLineFront;//弹弓皮筋前面    public LineRenderer catapultLineBack;//弹弓皮筋后面    private SpringJoint2D spring;//弹簧铰链    private Transform catapult;//弹弓    private Ray leftCatapultTpProjectile;//用来获取皮筋与投射物接触点的位置    private Ray rayToMouse;//用来限制物体的位置    private float maxStretchSql;//拉伸长度的平方    private Rigidbody2D rb;//刚体    private CircleCollider2D circle;//圆形碰撞器    private float circleRadius;//圆形碰撞器半径    private bool clickedOn;//判断是否是鼠标按下中    private Vector2 prevVelocity;//发射出去的速度    void Awake(){        spring = GetComponent<SpringJoint2D> ();        rb = GetComponent<Rigidbody2D> ();        circle = GetComponent<CircleCollider2D> ();        catapult = spring.connectedBody.transform;    }    // Use this for initialization    void Start () {        LineRendererSetUp ();        rayToMouse = new Ray (catapult.position,Vector3.zero);        leftCatapultTpProjectile = new Ray (catapultLineFront.transform.position,Vector3.zero);        maxStretchSql = maxStretch * maxStretch;        circleRadius = circle.radius;    }    // Update is called once per frame    void Update () {        if (clickedOn)            Dragging ();        if (spring != null) {//如果弹簧铰链不为空            if (!rb.isKinematic && prevVelocity.sqrMagnitude > rb.velocity.sqrMagnitude) {//如果投射物可以受力，且投射速度大于物体自身速度                Destroy (spring);//脱离铰链                rb.velocity = prevVelocity;//投射            }            if (!clickedOn)                prevVelocity = rb.velocity;//如果拖拽完成，投射速度等于物体自身的速度            LineRendererUpdate ();//更新弹弓皮筋        } else {            catapultLineFront.enabled = false;            catapultLineBack.enabled = false;        }    }    private void LineRendererSetUp(){//初始弹弓皮筋        catapultLineFront.SetPosition (0,catapultLineFront.transform.position);//设置皮筋与弹弓相连的点的位置        catapultLineBack.SetPosition (0,catapultLineBack.transform.position);        catapultLineFront.sortingLayerName = "ForeGround";//设置皮筋的渲染层        catapultLineBack.sortingLayerName = "ForeGround";        catapultLineFront.sortingOrder = 3;//设置同一层的渲染顺序        catapultLineBack.sortingOrder = 1;    }    void OnMouseDown(){        spring.enabled = false;//拖拽过程中,弹簧铰链失效        clickedOn = true;//拖拽中    }    void OnMouseUp(){        spring.enabled = true;//拖拽完后，恢复铰链        rb.isKinematic = false;//拖拽完后,使投射物受力        clickedOn = false;    }    private void Dragging (){//拖拽中持续更新物体位置        Vector3 mouseWordPoint = (Camera.main.ScreenToWorldPoint (Input.mousePosition));        Vector2 catapultToMouse = mouseWordPoint - catapult.position;        if (catapultToMouse.sqrMagnitude > maxStretchSql) {//限制拖拽长度            rayToMouse.direction = catapultToMouse;            mouseWordPoint = rayToMouse.GetPoint (maxStretch);//在射线的方向上找一个距离射线源点maxStretch的点        }        mouseWordPoint.z = 0;        transform.position = mouseWordPoint;    }    private void LineRendererUpdate(){//更新弹弓皮筋        Vector2 catapultToProjectile = transform.position-catapultLineFront.transform.position;        leftCatapultTpProjectile.direction = catapultToProjectile;        Vector3 holdPoint = leftCatapultTpProjectile.GetPoint (catapultToProjectile.magnitude+circleRadius);        catapultLineFront.SetPosition (1,holdPoint);        catapultLineBack.SetPosition (1,holdPoint);    }}

现在就已经可以投射了，但是相机是不动的

新建C#脚本ProjectileFollow并加到相机上

using UnityEngine;using System.Collections;public class ProjectileFollow : MonoBehaviour {    public Transform projectile;//投射物    public Transform farLeft;//相机左边界    public Transform farRight;//相机右边界    // Use this for initialization    void Start () {    }    // Update is called once per frame    void Update () {        Vector3 newPosition = transform.position;        newPosition.x = projectile.position.x;        newPosition.x = Mathf.Clamp (newPosition.x,farLeft.position.x,farRight.position.x);//限定相机的位置        transform.position = newPosition;    }}

在场景中新建三个空物体分别为，Boundary,Left,Right,且Left，Right为Boundary的子物体，修改Left，Right的tag图标(容易区分),在Scene视图中摆好位置

现在基本上完成了

最后加一个游戏重置的功能

在场景中新建一个空物体叫BoundaryCollider,并添加Box Collider2D,调整大小使它将整个场景包起来

这里需要注意一点，我们把BoundaryCollider的z坐标设为了1，只要不是0就行，原因是如果设为0有时鼠标会点在BoundaryCollider上，Asteroid就点不到了，虽然BoundaryCollider的z设为了1但是还是可以触发碰撞

最后新建C#脚本Resetter并挂到BoundaryCollider上

using UnityEngine;using System.Collections;using UnityEngine.SceneManagement;public class Resetter : MonoBehaviour {    public Rigidbody2D projectile;    // Use this for initialization    void Start () {    }    // Update is called once per frame    void Update () {        if (Input.GetKeyDown (KeyCode.R))            ReSet ();    }    void OnTriggerExit2D(Collider2D col){        if (col.GetComponent<Rigidbody2D> () == projectile)            ReSet ();    }    private void ReSet(){        SceneManager.LoadScene (SceneManager.GetActiveScene().name);    }}

好，完事！