Unity3D+VuforiaOffTarget的原理与实现方法。

模型OffTarget的原理：通过脚本实现图片识别之后，当识别图离开镜头的时候将模型固定在镜头前。

模型OffTarget的实现方法:第一步先搭建Vuforia的基础开发环境，具体流程可参照备注：http://manew.com/thread-100442-1-1.html，

1、在Hierrarchy视图空白处右键，创建一个空物体，命名为OffTargetPositionObject，拖到Camera物体下。

2、将要进行OffTarget的物体拖到OffTargetPositionObject下，并移动OffTargetPositionObject到ArCamera前，此时要保证OffTarget的物体在OffTargetPositonObject物体下的position为0。

3、在ImageTarget下面新建一个空物体，命名为Mgr，将要OffTarget的物体到Mgr下，保证Mgr和物体position为0。

4、此时，我们新建两个C#脚本，一个命名为OffTargetTrackableEventHandler，一个命名为OffTargetMgr。

6、打开ImageTarget上的DefaultTrackableEventHandler脚本，按Ctrl+A全选Ctrl+C复制，打开OffTargetTrackableEventHandler脚本，Ctrl+A全选，Ctrl+V粘贴，记住修改类名与脚本名保持一致，否则会报错。

7、打开OffTargetMgr脚本，键入以下代码

using System.Collections;using System.Collections.Generic;using UnityEngine;public class OffTargetMgr : MonoBehaviour {    //要OffTarget的物体    public GameObject OffTargetObject;    //摄像机下的物体    public GameObject OffTargetPositionObject;// Use this for initializationvoid Start () {}// Update is called once per framevoid Update () {}    void OnEnable()    {        //在此脚本启用时，将OffTarget的父物体设定为挂载了这个脚本的物体，并且把本地位置和本地角度设置为0。        OffTargetObject.transform.parent = this.transform;        OffTargetObject.transform.localPosition = new Vector3(0, 0, 0);        OffTargetObject.transform.localEulerAngles = new Vector3(0, 0, 0);    }    void OnDisable()    {        //在此脚本关闭时，将OffTarget的父物体设定为摄像机下的空物体，并且把本地位置和本地角度设置0。        OffTargetObject.transform.parent = OffTargetPositionObject.transform;        OffTargetObject.transform.localPosition = new Vector3(0, 0, 0);        OffTargetObject.transform.localEulerAngles = new Vector3(0, 0, 0);    }}

8、将OffTargetMgr挂载在ImageTarget下的Mgr上，并将要OffTarget的物体和OffTargetPositionObject物体拖入，并将OffTargetMgr脚本关闭勾选。

9、将ImageTarget物体上的DefaultTrackableEventHandler脚本Remove Component，将OffTargetTrackableEventHandler挂载在ImageTarget上。

10、在OffTargetTrackableEventHandler脚本中键入以下代码

/*==============================================================================Copyright (c) 2010-2014 Qualcomm Connected Experiences, Inc.All Rights Reserved.Confidential and Proprietary - Protected under copyright and other laws.==============================================================================*/using UnityEngine;namespace Vuforia{    /// <summary>    /// A custom handler that implements the ITrackableEventHandler interface.    /// </summary>    public class OffTargetTrackableEventHandler : MonoBehaviour,                                                ITrackableEventHandler    {        #region PRIVATE_MEMBER_VARIABLES        private TrackableBehaviour mTrackableBehaviour;        #endregion // PRIVATE_MEMBER_VARIABLES        #region UNTIY_MONOBEHAVIOUR_METHODS        void Start()        {            mTrackableBehaviour = GetComponent<TrackableBehaviour>();            if (mTrackableBehaviour)            {                mTrackableBehaviour.RegisterTrackableEventHandler(this);            }        }        #endregion // UNTIY_MONOBEHAVIOUR_METHODS        #region PUBLIC_METHODS        /// <summary>        /// Implementation of the ITrackableEventHandler function called when the        /// tracking state changes.        /// </summary>        public void OnTrackableStateChanged(                                        TrackableBehaviour.Status previousStatus,                                        TrackableBehaviour.Status newStatus)        {            if (newStatus == TrackableBehaviour.Status.DETECTED ||                newStatus == TrackableBehaviour.Status.TRACKED ||                newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)            {                OnTrackingFound();            }            else            {                OnTrackingLost();            }        }        #endregion // PUBLIC_METHODS        #region PRIVATE_METHODS        private void OnTrackingFound()        {            //获取这个物体下的第一个子物体上的OffTargetMgr脚本，并且启用它。            this.transform.GetChild(0).GetComponent<OffTargetMgr>().enabled = true;            Renderer[] rendererComponents = GetComponentsInChildren<Renderer>(true);            Collider[] colliderComponents = GetComponentsInChildren<Collider>(true);            // Enable rendering:            foreach (Renderer component in rendererComponents)            {                component.enabled = true;            }            // Enable colliders:            foreach (Collider component in colliderComponents)            {                component.enabled = true;            }            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");        }        private void OnTrackingLost()        {            //获取这个物体下的第一个子物体上的OffTargetMgr脚本，并且关闭它。            this.transform.GetChild(0).GetComponent<OffTargetMgr>().enabled = false;            Renderer[] rendererComponents = GetComponentsInChildren<Renderer>(true);            Collider[] colliderComponents = GetComponentsInChildren<Collider>(true);            // Disable rendering:            foreach (Renderer component in rendererComponents)            {                component.enabled = false;            }            // Disable colliders:            foreach (Collider component in colliderComponents)            {                component.enabled = false;            }            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " lost");        }        #endregion // PRIVATE_METHODS    }}

11、保存并且运行，模型内容OffTarget完成。

视频OffTarget的原理：通过脚本实现图片识别之后，当识别图离开镜头的时候将视频自动全屏播放或在镜头前播放。
视频OffTarget的实现方法：搭建视频播放的环境，具体流程可参照备注：http://blog.csdn.net/wene_zheng/article/details/52223958

1~3步和上面的一样，都是在Camera下面创建一个空物体。

4、新建两个脚本，分别命名为VideoOffTargetMgr和VideoTrackableEventHandler。

5、复制TrackableEventHandler内容到VideoTrackableEventHandler脚本里，记得修改类名，然后将ImageTarget上的TrackableEventHandler去掉换成VideoTrackableEventHandler，VideoTrackableEventHandler脚本内容如下。

/*==============================================================================  * Copyright (c) 2012-2015 Qualcomm Connected Experiences, Inc. All Rights Reserved.  * ==============================================================================*/using UnityEngine;using Vuforia;/// <summary>/// A custom handler that implements the ITrackableEventHandler interface./// </summary>public class VideoTrackableEventHandler : MonoBehaviour, ITrackableEventHandler{    #region PRIVATE_MEMBERS    private TrackableBehaviour mTrackableBehaviour;    private bool mHasBeenFound = false;    private bool mLostTracking;    private float mSecondsSinceLost;    #endregion // PRIVATE_MEMBERS    #region MONOBEHAVIOUR_METHODS    void Start()    {        mTrackableBehaviour = GetComponent<TrackableBehaviour>();        if (mTrackableBehaviour)        {            mTrackableBehaviour.RegisterTrackableEventHandler(this);        }        OnTrackingLost();    }    void Update()    {        // Pause the video if tracking is lost for more than two seconds        if (mHasBeenFound && mLostTracking)        {            if (mSecondsSinceLost > 2.0f)            {                VideoPlaybackBehaviour video = GetComponentInChildren<VideoPlaybackBehaviour>();                if (video != null &&                    video.CurrentState == VideoPlayerHelper.MediaState.PLAYING)                {                    video.VideoPlayer.Pause();                }                mLostTracking = false;            }            mSecondsSinceLost += Time.deltaTime;        }    }    #endregion //MONOBEHAVIOUR_METHODS    #region PUBLIC_METHODS    /// <summary>    /// Implementation of the ITrackableEventHandler function called when the    /// tracking state changes.    /// </summary>    public void OnTrackableStateChanged(                                    TrackableBehaviour.Status previousStatus,                                    TrackableBehaviour.Status newStatus)    {        if (newStatus == TrackableBehaviour.Status.DETECTED ||            newStatus == TrackableBehaviour.Status.TRACKED ||            newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)        {            OnTrackingFound();        }        else        {            OnTrackingLost();        }    }    #endregion //PUBLIC_METHODS    #region PRIVATE_METHODS    private void OnTrackingFound()    {        this.transform.GetChild(0).GetComponent<VideoOffTargetMgr>().enabled = true;        Renderer[] rendererComponents = GetComponentsInChildren<Renderer>();        Collider[] colliderComponents = GetComponentsInChildren<Collider>();        // Enable rendering:        foreach (Renderer component in rendererComponents)        {            component.enabled = true;        }        // Enable colliders:        foreach (Collider component in colliderComponents)        {            component.enabled = true;        }        Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");        // Optionally play the video automatically when the target is found        VideoPlaybackBehaviour video = GetComponentInChildren<VideoPlaybackBehaviour>();        if (video != null && video.AutoPlay)        {            if (video.VideoPlayer.IsPlayableOnTexture())            {                VideoPlayerHelper.MediaState state = video.VideoPlayer.GetStatus();                if (state == VideoPlayerHelper.MediaState.PAUSED ||                    state == VideoPlayerHelper.MediaState.READY ||                    state == VideoPlayerHelper.MediaState.STOPPED)                {                    // Pause other videos before playing this one                    PauseOtherVideos(video);                    // Play this video on texture where it left off                    video.VideoPlayer.Play(false, video.VideoPlayer.GetCurrentPosition());                }                else if (state == VideoPlayerHelper.MediaState.REACHED_END)                {                    // Pause other videos before playing this one                    PauseOtherVideos(video);                    // Play this video from the beginning                    video.VideoPlayer.Play(false, 0);                }            }        }        mHasBeenFound = true;        mLostTracking = false;    }    private void OnTrackingLost()    {        this.transform.GetChild(0).GetComponent<VideoOffTargetMgr>().enabled = false;        Renderer[] rendererComponents = GetComponentsInChildren<Renderer>();        Collider[] colliderComponents = GetComponentsInChildren<Collider>();        // Disable rendering:        foreach (Renderer component in rendererComponents)        {            component.enabled = false;        }        // Disable colliders:        foreach (Collider component in colliderComponents)        {            component.enabled = false;        }        Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " lost");        mLostTracking = true;        mSecondsSinceLost = 0;    }    // Pause all videos except this one    private void PauseOtherVideos(VideoPlaybackBehaviour currentVideo)    {        VideoPlaybackBehaviour[] videos = (VideoPlaybackBehaviour[])                FindObjectsOfType(typeof(VideoPlaybackBehaviour));        foreach (VideoPlaybackBehaviour video in videos)        {            if (video != currentVideo)            {                if (video.CurrentState == VideoPlayerHelper.MediaState.PLAYING)                {                    video.VideoPlayer.Pause();                }            }        }    }    #endregion //PRIVATE_METHODS}

6、将VideoOffTarget脚本挂在ImageTarget物体下的Mgr上，VideoOffTarget脚本内容如下

using System.Collections;using System.Collections.Generic;using UnityEngine;public class VideoOffTargetMgr : MonoBehaviour {    public GameObject VideoObject;    public GameObject OffTargetObject;// Use this for initializationvoid Start () {}// Update is called once per framevoid Update () {}    void OnEnable()    {        VideoObject.transform.parent = this.transform;        VideoObject.transform.position = new Vector3(0,0,0);        VideoObject.transform.eulerAngles = new Vector3(0, 0, 0);    }    void OnDisable()    {        VideoObject.transform.parent = OffTargetObject.transform;        VideoObject.transform.position = new Vector3(0, 0, 0);        VideoObject.transform.eulerAngles = new Vector3(0, 0, 0);        /*全屏播放方法如下        Handheld.PlayFullScreenMovie("VuforiaSizzleReel_1.mp4", Color.black, FullScreenMovieControlMode.CancelOnInput);        括号中第一个参数为视频路径，第二个为背景颜色，第三个为播放模式。*/            }}

7、打包成安卓或者IOS包，在手机上运行，电脑上无法播放视频（使用Vuforia自带视频插件时）。