此腳本作用是持續(xù)時(shí)間內(nèi)將眼鏡的視圖顏色更改為指定的顏色；
在場(chǎng)景區(qū)域周圍有碰撞的墻壁時(shí)，如果用戶將頭部插入墻壁，則視圖會(huì)褪色為指定的顏色，一般選黑色；
PlayArea對(duì)象上掛在此腳本；
命名空間：VRTK

HeadsetFadeEventArgs 結(jié)構(gòu)體

眼鏡淡出事件參數(shù) 此處是結(jié)構(gòu)體包含兩個(gè)參數(shù)：
public float timeTillComplete;// 時(shí)間
public Transform currentTransform;//當(dāng)前對(duì)象Camera

委托：

public delegate void HeadsetFadeEventHandler(object sender, HeadsetFadeEventArgs e); 眼鏡淡出事件處理的委托 參數(shù)有發(fā)出者，上述結(jié)構(gòu)體參數(shù)

事件：

對(duì)應(yīng)上述委托四個(gè)事件
public event HeadsetFadeEventHandler HeadsetFadeStart; //當(dāng)用戶的頭戴式設(shè)備開(kāi)始褪色到特定顏色時(shí)發(fā)出。
public event HeadsetFadeEventHandler HeadsetFadeComplete;//當(dāng)用戶的頭戴式設(shè)備完成淡入淡出并且現(xiàn)在完全處于給定顏色時(shí)發(fā)出。
public event HeadsetFadeEventHandler HeadsetUnfadeStart;//當(dāng)用戶的耳機(jī)開(kāi)始恢復(fù)到透明顏色時(shí)發(fā)出。
public event HeadsetFadeEventHandler HeadsetUnfadeComplete;//當(dāng)用戶的頭戴式設(shè)備完成非透明設(shè)置并再次完全透明時(shí)發(fā)出。

三個(gè)用到的字段：

protected Transform headset;//頭部
protected bool isTransitioning = false;
protected bool isFaded = false;

 public virtual void OnHeadsetFadeStart(HeadsetFadeEventArgs e)
    {
        if (HeadsetFadeStart != null)
        {
            HeadsetFadeStart(this, e);
        }
    }

    public virtual void OnHeadsetFadeComplete(HeadsetFadeEventArgs e)
    {
        if (HeadsetFadeComplete != null)
        {
            HeadsetFadeComplete(this, e);
        }
    }

    public virtual void OnHeadsetUnfadeStart(HeadsetFadeEventArgs e)
    {
        if (HeadsetUnfadeStart != null)
        {
            HeadsetUnfadeStart(this, e);
        }
    }

    public virtual void OnHeadsetUnfadeComplete(HeadsetFadeEventArgs e)
    {
        if (HeadsetUnfadeComplete != null)
        {
            HeadsetUnfadeComplete(this, e);
        }
    }

上述是處理四個(gè)事件的方法，可以進(jìn)行重寫(xiě)；

IsFaded()方法返回isFaded 的bool值，如果當(dāng)前正在褪色或已經(jīng)完全褪色，返回true，如果完全未褪色返回false；
IsTransitioning()方法返回isTransitioning 的bool值，如果眼鏡當(dāng)前正在褪色或不褪色返回真，如果眼鏡視野完全褪色或未褪色返回假；
Fade(Color color, float duration)方法：在給定的持續(xù)時(shí)間duration內(nèi)將耳機(jī)視圖的顏色更改為給定的顏色color；
Unfade(float duration)方法：在給定的時(shí)間內(nèi)將顏色更改為透明顏色。

余下方法是protected修飾的，腳本內(nèi)部調(diào)用的；

Awake() 調(diào)用VRTK_SDKManager類里的一個(gè)Add方法
OnEnable() 給三個(gè)參數(shù)賦初始值和 調(diào)用VRTK_SharedMethods類的一個(gè)AddCameraFade方法；
OnDestroy() 調(diào)用VRTK_SDKManager類里的一個(gè)Remove方法，和Awake相呼應(yīng)；
SetHeadsetFadeEvent方法：返回上面定義的一個(gè)枚舉；
FadeComplete()方法：Fade和UnFade里調(diào)用；
UnfadeComplete()方法：Fade和UnFade里調(diào)用；

 // Headset Fade|Presence|70020
namespace VRTK
{
 using UnityEngine;
/// <summary>
/// Event Payload
/// </summary>
/// <param name="timeTillComplete">A float that is the duration for the fade/unfade process has remaining.</param>
/// <param name="currentTransform">The current Transform of the object that the Headset Fade script is attached to (Camera).</param>
public struct HeadsetFadeEventArgs
{
    public float timeTillComplete;
    public Transform currentTransform;
}

/// <summary>
/// Event Payload
/// </summary>
/// <param name="sender">this object</param>
/// <param name="e"><see cref="HeadsetFadeEventArgs"/></param>
public delegate void HeadsetFadeEventHandler(object sender, HeadsetFadeEventArgs e);

/// <summary>
/// Provides the ability to change the colour of the headset view to a specified colour over a given duration.
/// </summary>
/// <remarks>
/// **Script Usage:**
///  * Place the `VRTK_HeadsetFade` script on any active scene GameObject.
/// </remarks>
/// <example>
/// `VRTK/Examples/011_Camera_HeadSetCollisionFading` has collidable walls around the play area and if the user puts their head into any of the walls then the headset will fade to black.
/// </example>
[AddComponentMenu("VRTK/Scripts/Presence/VRTK_HeadsetFade")]
public class VRTK_HeadsetFade : MonoBehaviour
{
    /// <summary>
    /// Emitted when the user's headset begins to fade to a given colour.
    /// </summary>
    public event HeadsetFadeEventHandler HeadsetFadeStart;
    /// <summary>
    /// Emitted when the user's headset has completed the fade and is now fully at the given colour.
    /// </summary>
    public event HeadsetFadeEventHandler HeadsetFadeComplete;
    /// <summary>
    /// Emitted when the user's headset begins to unfade back to a transparent colour.
    /// </summary>
    public event HeadsetFadeEventHandler HeadsetUnfadeStart;
    /// <summary>
    /// Emitted when the user's headset has completed unfading and is now fully transparent again.
    /// </summary>
    public event HeadsetFadeEventHandler HeadsetUnfadeComplete;

    protected Transform headset;
    protected bool isTransitioning = false;
    protected bool isFaded = false;

    public virtual void OnHeadsetFadeStart(HeadsetFadeEventArgs e)
    {
        if (HeadsetFadeStart != null)
        {
            HeadsetFadeStart(this, e);
        }
    }

    public virtual void OnHeadsetFadeComplete(HeadsetFadeEventArgs e)
    {
        if (HeadsetFadeComplete != null)
        {
            HeadsetFadeComplete(this, e);
        }
    }

    public virtual void OnHeadsetUnfadeStart(HeadsetFadeEventArgs e)
    {
        if (HeadsetUnfadeStart != null)
        {
            HeadsetUnfadeStart(this, e);
        }
    }

    public virtual void OnHeadsetUnfadeComplete(HeadsetFadeEventArgs e)
    {
        if (HeadsetUnfadeComplete != null)
        {
            HeadsetUnfadeComplete(this, e);
        }
    }

    /// <summary>
    /// The IsFaded method returns true if the headset is currently fading or has completely faded and returns false if it is completely unfaded.
    /// </summary>
    /// <returns>Returns `true` if the headset is currently fading or faded.</returns>
    public virtual bool IsFaded()
    {
        return isFaded;
    }

    /// <summary>
    /// The IsTransitioning method returns true if the headset is currently fading or unfading and returns false if it is completely faded or unfaded.
    /// </summary>
    /// <returns>Returns `true` if the headset is currently in the process of fading or unfading.</returns>
    public virtual bool IsTransitioning()
    {
        return isTransitioning;
    }

    /// <summary>
    /// The Fade method initiates a change in the colour of the headset view to the given colour over a given duration.
    /// </summary>
    /// <param name="color">The colour to fade the headset view to.</param>
    /// <param name="duration">The time in seconds to take to complete the fade transition.</param>
    public virtual void Fade(Color color, float duration)//
    {
        isFaded = false;//此時(shí)為假
        isTransitioning = true;//此時(shí)為真
        VRTK_SDK_Bridge.HeadsetFade(color, duration);
        OnHeadsetFadeStart(SetHeadsetFadeEvent(headset, duration));//執(zhí)行事件SetHeadsetFadeEvent(headset, duration)方法返回定義的的枚舉
        CancelInvoke("UnfadeComplete");//取消UnfadeComplete方法在這個(gè)腳本中所有的調(diào)用 
        Invoke("FadeComplete", duration);// duration時(shí)間后執(zhí)行FadeComplete方法
    }

    /// <summary>
    /// The Unfade method initiates the headset to change colour back to a transparent colour over a given duration.
    /// </summary>
    /// <param name="duration">The time in seconds to take to complete the unfade transition.</param>
    public virtual void Unfade(float duration)
    {
        isFaded = true;
        isTransitioning = true;
        VRTK_SDK_Bridge.HeadsetFade(Color.clear, duration);
        OnHeadsetUnfadeStart(SetHeadsetFadeEvent(headset, duration));
        CancelInvoke("FadeComplete");
        Invoke("UnfadeComplete", duration);
    }

    protected virtual void Awake()
    {
        VRTK_SDKManager.AttemptAddBehaviourToToggleOnLoadedSetupChange(this);
    }

    protected virtual void OnEnable()
    {
        headset = VRTK_DeviceFinder.HeadsetCamera();
        isTransitioning = false;
        isFaded = false;

        VRTK_SharedMethods.AddCameraFade();
    }

    protected virtual void OnDestroy()
    {
        VRTK_SDKManager.AttemptRemoveBehaviourToToggleOnLoadedSetupChange(this);
    }

    protected virtual HeadsetFadeEventArgs SetHeadsetFadeEvent(Transform currentTransform, float duration)
    {
        HeadsetFadeEventArgs e;
        e.timeTillComplete = duration;
        e.currentTransform = currentTransform;
        return e;
    }

    protected virtual void FadeComplete()
    {
        isFaded = true;//談出完成
        isTransitioning = false;
        OnHeadsetFadeComplete(SetHeadsetFadeEvent(headset, 0f));//事件執(zhí)行
    }

    protected virtual void UnfadeComplete()
    {
        isFaded = false;//恢復(fù)透明色完成
        isTransitioning = false;
        OnHeadsetUnfadeComplete(SetHeadsetFadeEvent(headset, 0f));
    }
}
}