Vuforia_DefinedTarget的使用

重要的脚本：

1.User DefinedTargetBuilding Behaviour

2.UDT Event Handler(自定义，继承于 IUserDefinedTargetEventHandler)

3.Image Target Behaviour

4.Default Trackable Event Handler(自定义，继承于 ITrackableEventHandler)

 案例使用（脚本解读）

UDT Event Handler.cs

 实例化一个新的用户定义目标，还负责将回调分派到IUserDefinedTargetEventHandler :: OnNewTrackableSource

 public void BuildwNewTarget()
    {
        if (m_FrameQuality == ImageTargetBuilder.FrameQuality.FRAME_QUALITY_MEDIUM ||
            m_FrameQuality == ImageTargetBuilder.FrameQuality.FRAME_QUALITY_HIGH)
        {

            //创建下一个目标的名称。 原始的链接ImageTargetBehaviour的TrackableName扩展了一个连续的数字，以确保唯一的名称
            string targetName = string.Format("{0}-{1}", ImageTargetTemplate.TrackableName, m_TargetCounter);

            // 生成 a new target:
            m_TargetBuildingBehaviour.BuildNewTarget(targetName, ImageTargetTemplate.GetSize().x);
        }
        else
        {
            Debug.Log("Cannot build new target, due to poor camera image quality");
            StatusMessage.Instance.Display("Low camera image quality", true);
        }
    }

 成功初始化UserDefinedTargetBuildingBehaviour时调用

 public void OnInitialized()
    {
        m_ObjectTracker = TrackerManager.Instance.GetTracker<ObjectTracker>();
        if (m_ObjectTracker != null)
        {
            // Create a new dataset
            m_UDT_DataSet = m_ObjectTracker.CreateDataSet();
            m_ObjectTracker.ActivateDataSet(m_UDT_DataSet);
        }
    }

更新当前帧质量

public void OnFrameQualityChanged(ImageTargetBuilder.FrameQuality frameQuality)
    {
        Debug.Log("Frame quality changed: " + frameQuality.ToString());
        m_FrameQuality = frameQuality;
        if (m_FrameQuality == ImageTargetBuilder.FrameQuality.FRAME_QUALITY_LOW)
        {
            Debug.Log("Low camera image quality");
        }

        m_FrameQualityMeter.SetQuality(frameQuality);
    }

取得一个新的可跟踪源并将其添加到数据集中。一旦您使用UserDefinedTargetBuildingBehaviour BuildNewTarget，就会自动调用该源

public void OnNewTrackableSource(TrackableSource trackableSource)
    {
        m_TargetCounter++;

        // Deactivates the dataset first
        m_ObjectTracker.DeactivateDataSet(m_UDT_DataSet);

        // Destroy the oldest target if the dataset is full or the dataset
        // already contains five user-defined targets.
        if (m_UDT_DataSet.HasReachedTrackableLimit() || m_UDT_DataSet.GetTrackables().Count() >= MAX_TARGETS)
        {
            IEnumerable<Trackable> trackables = m_UDT_DataSet.GetTrackables();
            Trackable oldest = null;
            foreach (Trackable trackable in trackables)
            {
                if (oldest == null || trackable.ID < oldest.ID)
                    oldest = trackable;
            }

            if (oldest != null)
            {
                Debug.Log("Destroying oldest trackable in UDT dataset: " + oldest.Name);
                m_UDT_DataSet.Destroy(oldest, true);
            }
        }

        // Get predefined trackable and instantiate it
        //获取预定义的可跟踪并将其实例化
        ImageTargetBehaviour imageTargetCopy = Instantiate(ImageTargetTemplate);
        imageTargetCopy.gameObject.name = "UserDefinedTarget-" + m_TargetCounter;

        // Add the duplicated trackable to the data set and activate it
        m_UDT_DataSet.CreateTrackable(trackableSource, imageTargetCopy.gameObject);

        // Activate the dataset again
        m_ObjectTracker.ActivateDataSet(m_UDT_DataSet);

        // Make sure TargetBuildingBehaviour keeps scanning...
        m_TargetBuildingBehaviour.StartScanning();
    }