Unity3D 利用FSM设计相机跟随实现

笔者介绍：姜雪伟，IT公司技术合伙人，IT高级讲师，CSDN社区专家，特邀编辑，畅销书作者，国家专利发明人;已出版书籍：《手把手教你架构3D游戏引擎》电子工业出版社和《Unity3D实战核心技术详解》电子工业出版社等。

CSDN视频网址：http://edu.csdn.net/lecturer/144

FSM有限状态机前面已经跟读者介绍过，使用Unity3D引擎实现了动作状态以及技能切换，FSM使用的条件是有限个状态切换，我们可以将FSM应用到相机中，很多人会问在相机中如何使用FSM，不论那种架构其主要目的是将模块之间的耦合性降低，传统的写法就是使用一个相机跟随类，所有的逻辑一股脑的写在一个类或者两个类中，这样一旦逻辑变动，修改起来非常麻烦，可能修改的就不是一个类两个类的事情，而如果我们采用FSM设计相机跟随，这样就容易多了。

接下来就实现FSM有限状态机，FSM作为一个通用类需要将其设置成模版的方式，具体代码如下所示：

using System;using System.Collections.Generic;namespace Core{    public class FSM    {        public class Object<T, K>            where T : Object<T, K>        {            public delegate void Function(T self, float time);            #region Protected members            protected TimeSource timeSource = null;            protected Dictionary<K, State<T, K>> states = new Dictionary<K,State<T,K>>();            protected State<T, K> state = null;            protected State<T, K> prevState = null;            #endregion            #region Ctors            public Object()            {                timeSource = TimeManager.Instance.MasterSource;            }            public Object(TimeSource source)            {                timeSource = source;            }            #endregion            #region Public properties            public K PrevState            {                get                {                    return prevState.key;                }            }            public K State            {                get                {                    return state.key;                }                set                {                    prevState = state;                    if (prevState != null)                        prevState.onExit(this as T, timeSource.TotalTime);                    State<T, K> nextState;                    if (states.TryGetValue(value, out nextState))                    {                        state = nextState;                        state.onEnter(this as T, timeSource.TotalTime);                    }                    else                    {                        state = null;                    }                }            }            public TimeSource TimeSource            {                get                {                    return timeSource;                }                set                {                    timeSource = value;                }            }            #endregion            #region Public methods            public void AddState(K key, Function onEnter, Function onExec, Function onExit)            {                State<T, K> newState = new State<T, K>();                newState.key = key;                newState.onEnter = onEnter;                newState.onExec = onExec;                newState.onExit = onExit;                states.Add(key, newState);            }            public void Update()            {                if (null == state) return;                state.onExec(this as T, timeSource.TotalTime);            }            #endregion        }        public class State<T, K>            where T : Object<T, K>        {            public K key;            public Object<T, K>.Function onEnter;            public Object<T, K>.Function onExec;            public Object<T, K>.Function onExit;        }    }}

在这个类中有三部分最重要，第一部分是定义了状态类，它实现了状态的切换函数，onEnter，onExec，onExit，这个是作为状态切换使用的。代码如下：

        public class State<T, K>            where T : Object<T, K>        {            public K key;            public Object<T, K>.Function onEnter;            public Object<T, K>.Function onExec;            public Object<T, K>.Function onExit;        }

另一个类的函数是增加状态函数，这个需要在Start函数中去执行的，函数代码如下所示：

            public void AddState(K key, Function onEnter, Function onExec, Function onExit)            {                State<T, K> newState = new State<T, K>();                newState.key = key;                newState.onEnter = onEnter;                newState.onExec = onExec;                newState.onExit = onExit;                states.Add(key, newState);            }

最后一个函数就是Update函数，需要每帧去检测执行状态，函数如下所示：

            public void Update()            {                if (null == state) return;                state.onExec(this as T, timeSource.TotalTime);            }

这三个是最重要的，必须要有的，接下来编写挂接到对象上的类FiniteStateMachine类脚本，代码如下所示：

using System;using System.Collections.Generic;using UnityEngine;using Core;public class FiniteStateMachine : MonoBehaviour{public enum UpdateFunction{Update = 0,LateUpdate,FixedUpdate}#region Public classespublic class FSMObject : FSM.Object<FSMObject, int>{public GameObject go;public FSMObject(GameObject _go){go = _go;}}[Serializable]public class StateType{public int id;public string onEnterMessage;public string onExecMessage;public string onExitMessage;public void onEnter(FSMObject fsmObject, float time){fsmObject.go.SendMessage(onEnterMessage, time, SendMessageOptions.RequireReceiver);}public void onExec(FSMObject fsmObject, float time){fsmObject.go.SendMessage(onExecMessage, time, SendMessageOptions.RequireReceiver);}public void onExit(FSMObject fsmObject, float time){fsmObject.go.SendMessage(onExitMessage, time, SendMessageOptions.RequireReceiver);}}#endregion#region Public memberspublic bool manualUpdate = false;public UpdateFunction updateFunction = UpdateFunction.Update;public StateType[] states;public int startState;#endregion#region Protected membersprotected FSMObject fsmObject = null;#endregion#region Public propertiespublic int PrevState{get{return fsmObject.PrevState;}}public int State{get{return fsmObject.State;}set{fsmObject.State = value;}}public TimeSource TimeSource{get{return fsmObject.TimeSource;}set{fsmObject.TimeSource = value;}}#endregion#region Public methodspublic void ForceUpdate(){fsmObject.Update();}#endregion#region Unity callbacksprotected void Start(){fsmObject = new FSMObject(gameObject);foreach (StateType state in states)fsmObject.AddState(state.id, state.onEnter, state.onExec, state.onExit);fsmObject.State = startState;}void Update(){//Debug.Log ("update");if (manualUpdate)return;if (UpdateFunction.Update == updateFunction)fsmObject.Update();}void LateUpdate(){if (manualUpdate)return;if (UpdateFunction.LateUpdate == updateFunction)fsmObject.Update();}void FixedUpdate(){if (manualUpdate)return;if (UpdateFunction.FixedUpdate == updateFunction)fsmObject.Update();}#endregion}

该函数需要挂接到对象上，效果如下所示：

以上就是我们所封装的FSM有限状态机，接下来在项目中使用我们的FSM，先实现最基本的逻辑类如下所示：

using System;using System.Collections.Generic;using UnityEngine;public class FollowCharacter : MonoBehaviour{public GameObject player;public Vector3 sourceOffset = new Vector3(0.0f, 2.5f, -3.4f);public Vector3 targetOffset = new Vector3(0.0f, 1.7f, 0.0f);protected bool firstFrame;protected float currHeightSmoothing;protected float groundHeightTest;protected bool slideshowActive = false;protected float slideshowEnterTime = 0.0f;protected float slideshowExitTime = 0.0f;protected bool oldCameraActive = true;protected float oldFov = 70.0f;protected Vector3 oldCamSourceOffset = new Vector3(0.0f, 8.5f, -4.5f);protected Vector3 oldCamTargetOffset = new Vector3(0.0f, 0.9f, 5.3f);protected int cameraIndex = 3;protected float[] cameraFovs = { 55.0f, 60.0f, 55.0f };protected Vector3[] cameraSourceOffsets = {new Vector3(0.0f, 5.8f, -3.8f),new Vector3(0.0f, 6.04f, -4.0f),new Vector3(0.0f, 8.5f, -6.7f)};protected Vector3[] cameraTargetOffsets = {new Vector3(0.0f, 2.2f, 2.5f),new Vector3(0.0f, 1.35f, 3.36f),new Vector3(0.0f, 1.45f, 5.3f)};protected Vector3 newCamSourceOffset = new Vector3(0.0f, 6.04f, -4.0f);//Camera 2protected Vector3 newCamTargetOffset = new Vector3(0.0f, 1.35f, 3.36f);//Camera 2protected Vector3 testNewTurboSourceOffset = new Vector3(0.0f, 5.8f, -4.0f);protected Vector3 testNewTurboTargetOffset = new Vector3(0.0f, 2.1f, 2.5f);protected Vector3 testNewFinalSourceOffset = new Vector3(-6.5f, 5.0f, -5.5f);protected Vector3 testNewFinalTargetOffset = new Vector3(-4.5f, 1.7f, 0.0f);

#region public Classespublic class ShakeData{public float duration;public float noise;public float smoothTime;public ShakeData(float _duration, float _noise, float _smoothTime){duration = _duration;noise = _noise;smoothTime = _smoothTime;}}#endregionpublic void OnFollowCharaEnter(float time){prevPlayerPivot = player.transform.position;firstFrame = true;currHeightSmoothing = heightSmoothing;deadTime = -1.0f;actionTaken = false;}public void OnFollowCharaExec(float time){if (player == null)return;float dt = Time.fixedDeltaTime;float now = TimeManager.Instance.MasterSource.TotalTime;Vector3 playerPivot = player.transform.position;playerPivot.x = 0.0f;playerPivot.y = 0.0f;float targetHeight = playerPivot.y;if (firstFrame){lastPivotHeight = targetHeight;prevPlayerPivot = playerPivot;heightVelocity = 0.0f;firstFrame = false;}else{float targetSmoothTime = 0.1f;smoothTime = Mathf.MoveTowards(smoothTime, targetSmoothTime, 2.5f * dt);lastPivotHeight = Mathf.SmoothDamp(lastPivotHeight, targetHeight, ref heightVelocity, smoothTime, 50.0f, dt);prevPlayerPivot = playerPivot;}Vector3 camPivot = new Vector3(prevPlayerPivot.x * 0.8f, lastPivotHeight, prevPlayerPivot.z);lastSourceOffset = this.EaseTo(lastSourceOffset, goalSourceOffset, sourceOffset);lastTargetOffset = this.EaseTo(lastTargetOffset, goalTargetOffset, targetOffset);transform.position = camPivot + lastSourceOffset + offset * 0.1f + noise * noiseStrength; // +noise * noiseStrength + noiseTremor * 0.00069f * kinematics.PlayerRigidbody.velocity.z; //PIETROtransform.LookAt(camPivot + lastTargetOffset + offset * 0.1f, Vector3.up);if (!TimeManager.Instance.MasterSource.IsPaused){//Camera Shakeif (shakeCameraActive)ShakeCamera(dt);//tremor (always activethis.UpdateTremor(dt);}//check if is deadif (now - deadTime > 3.6f && !actionTaken && deadTime > 0.0f){actionTaken = true;//Debug.Log("GO TO REWARD");LevelRoot.Instance.BroadcastMessage("GoToOffgame");     //GoToReward");}}public void OnFollowCharaExit(float time){}void OnReset(){//Debug.Log("RESET CAM");interpolating = false;shakeCameraActive = false;sourceOffset = defaultSourceOffset;targetOffset = defaultTargetOffset;}void ShakeCamera(float deltaTime){if (TimeManager.Instance.MasterSource.TotalTime - shakeStartTime <= currentShakeData.duration){if (currentShakeData.smoothTime > 0.0f)noiseStrength = Mathf.SmoothDamp(noiseStrength, currentShakeData.noise, ref noiseStrengthVel, currentShakeData.smoothTime, 300.0f, deltaTime);elsenoiseStrength = currentShakeData.noise; // go directlyif (noiseStrength > 0.0f){Vector3 v = UnityEngine.Random.onUnitSphere;noise += (v - noise) * deltaTime * 8.0f;}elsenoise = SRVector3.zero;}if (TimeManager.Instance.MasterSource.TotalTime - shakeStartTime >= currentShakeData.duration)StopShakeCamera();}void StopShakeCamera(){currentShakeData = new ShakeData(0.0f, 0.0f, 0.0f);noiseStrength = 0.0f;noise = SRVector3.zero;shakeCameraActive = false;}public string ChangeCamera(){string buttonText = "";buttonText = cameraIndex == 0 ? "Old camera on" : "camera " + cameraIndex + " on";if (cameraIndex == 0){gameObject.GetComponent<Camera>().fieldOfView = oldFov;lastSourceOffset = defaultSourceOffset = sourceOffset = oldCamSourceOffset;lastTargetOffset = defaultTargetOffset = targetOffset = oldCamTargetOffset;goalSourceOffset = oldCamSourceOffset;goalTargetOffset = oldCamTargetOffset;}else{gameObject.GetComponent<Camera>().fieldOfView = cameraFovs[cameraIndex - 1];lastSourceOffset = defaultSourceOffset = sourceOffset = cameraSourceOffsets[cameraIndex - 1];lastTargetOffset = defaultTargetOffset = targetOffset = cameraTargetOffsets[cameraIndex - 1];goalSourceOffset = cameraSourceOffsets[cameraIndex - 1];goalTargetOffset = cameraTargetOffsets[cameraIndex - 1];}return buttonText;}}

其中脚本中加粗的函数是有限状态机执行的具体逻辑。。。。。。。另外其他的变量声明和函数实现是根据策划需求添加的，读者只需要关注加粗的函数实现就可以了。
附图如下所示：