Hololens開發筆記之Gesture手勢識別（手勢檢測反饋）

本文實現當使用者手出現在Hololens視野范圍內時，跟蹤手並給出反饋的效果。

1、在Manager上添加HandsManager腳本組件，用於追蹤識別手

 

HandsManager.cs如下（直接使用HoloTooKit中腳本）

// Copyright (c) Microsoft Corporation. All rights reserved.  
// Licensed under the MIT License. See LICENSE in the project root for license information.  
  
using System.Collections.Generic;  
using UnityEngine.VR.WSA.Input;  
  
namespace HoloToolkit.Unity  
{  
    /// <summary>  
    /// HandsManager determines if the hand is currently detected or not.  
    /// </summary>  
    public partial class HandsManager : Singleton<HandsManager>  
    {  
        /// <summary>  
        /// HandDetected tracks the hand detected state.  
        /// Returns true if the list of tracked hands is not empty.  
        /// </summary>  
        public bool HandDetected  
        {  
            get { return trackedHands.Count > 0; }  
        }  
  
        private HashSet<uint> trackedHands = new HashSet<uint>();  
  
        void Awake()  
        {  
            //識別到來源  
            InteractionManager.SourceDetected += InteractionManager_SourceDetected;  
            //來源丟失  
            InteractionManager.SourceLost += InteractionManager_SourceLost;  
        }  
  
        private void InteractionManager_SourceDetected(InteractionSourceState state)  
        {  
            // 檢測來源是否為手，如果是手則加入跟蹤集合  
            if (state.source.kind != InteractionSourceKind.Hand)  
            {  
                return;  
            }  
  
            trackedHands.Add(state.source.id);  
        }  
  
        private void InteractionManager_SourceLost(InteractionSourceState state)  
        {  
            // 檢測丟失的來源是否為手，如果是手則從跟蹤集合中去除  
            if (state.source.kind != InteractionSourceKind.Hand)  
            {  
                return;  
            }  
  
            if (trackedHands.Contains(state.source.id))  
            {  
                trackedHands.Remove(state.source.id);  
            }  
        }  
  
        void OnDestroy()  
        {  
            InteractionManager.SourceDetected -= InteractionManager_SourceDetected;  
            InteractionManager.SourceLost -= InteractionManager_SourceLost;  
        }  
    }  
}  

該腳本中使用到了底層API   Interaction Input

底層API運行獲得輸入來源的更多詳細信息，例如它在世界中的位置和速度。

如何處理底層交互事件
使用底層交互是很容易的：
1） 注冊InteractionManager事件
2） 處理事件
停止它也很容易：
1） 取消注冊事件

處理底層交互事件
一旦注冊了底層交互事件，在事件發生時你就可以得到回調。你可以使用獲取到的時間信息來處理應用行為。

void InteractionManager_SourcePressed(InteractionSourceState state)  
{  
// state變量里包含以下信息:  
// 當前凝視射線信息  
// 來源是否被點擊  
// 位置、速度之類的屬性  
// 來源id和來源類型 （ hand, voice, controller或其他）  
}  

如何停止交互事件
當你不再想要關注一些事件后，只需要取消時間注冊即可。

InteractionManager.SourcePressed -= InteractionManager_SourcePressed;  

輸入源變化事件
這些事件描述了輸入源的當前狀態：
1) detected（ 即將激活）
2) lost（ 即將取消激活）
3) updates（ 移動或者一些狀態在變化）
4) is pressed（ 點擊、按鈕按下或者語音選中）
5) is released（ 點擊結束，按鈕松開，語音選中結束）


輸入源狀態
每個事件都會有一個InteractionSourceState參數，這個參數代表了實時輸入源狀態：
1) 是否是點擊狀態
2) InteractionSourceProperties包含了輸入源位置信息 InteractionSourceLocation，能夠獲得當前輸入源位置和速度信息
3) 凝視射線信息，用於判斷事件發生時用戶是否在注視目標
4) 來源類型信息，包括hand、voice、controller或者其他類型

2、在Cursor下新建Empty對象，並重命名為CursorBillboard，並添加Billboard腳本組件

 

Billboard腳本如下(可以直接在HoloToolKit中找到)

// Copyright (c) Microsoft Corporation. All rights reserved.  
// Licensed under the MIT License. See LICENSE in the project root for license information.  
  
using UnityEngine;  
  
namespace HoloToolkit.Unity  
{  
    public enum PivotAxis  
    {  
        // Rotate about all axes.  
        Free,  
        // Rotate about an individual axis.  
        X,  
        Y  
    }  
  
    /// <summary>  
    /// The Billboard class implements the behaviors needed to keep a GameObject  
    /// oriented towards the user.  
    /// </summary>  
    public class Billboard : MonoBehaviour  
    {  
        /// <summary>  
        /// The axis about which the object will rotate.  
        /// </summary>  
        [Tooltip("Specifies the axis about which the object will rotate (Free rotates about both X and Y).")]  
        public PivotAxis PivotAxis = PivotAxis.Free;  
  
        /// <summary>  
        /// Overrides the cached value of the GameObject's default rotation.  
        /// </summary>  
        public Quaternion DefaultRotation { get; private set; }  
  
        private void Awake()  
        {  
            // Cache the GameObject's default rotation.  
            DefaultRotation = gameObject.transform.rotation;  
        }  
  
        /// <summary>  
        /// Keeps the object facing the camera.  
        /// </summary>  
        private void Update()  
        {  
            // Get a Vector that points from the Camera to the target.  
            Vector3 forward;  
            Vector3 up;  
  
            // Adjust for the pivot axis. We need a forward and an up for use with Quaternion.LookRotation  
            switch (PivotAxis)  
            {  
                // If we're fixing one axis, then we're projecting the camera's forward vector onto  
                // the plane defined by the fixed axis and using that as the new forward.  
                case PivotAxis.X:  
                    Vector3 right = transform.right; // Fixed right  
                    forward = Vector3.ProjectOnPlane(Camera.main.transform.forward, right).normalized;  
                    up = Vector3.Cross(forward, right); // Compute the up vector  
                    break;  
  
                case PivotAxis.Y:  
                    up = transform.up; // Fixed up  
                    forward = Vector3.ProjectOnPlane(Camera.main.transform.forward, up).normalized;  
                    break;  
  
                // If the axes are free then we're simply aligning the forward and up vectors  
                // of the object with those of the camera.   
                case PivotAxis.Free:  
                default:  
                    forward = Camera.main.transform.forward;  
                    up = Camera.main.transform.up;  
                    break;  
            }  
  
  
            // Calculate and apply the rotation required to reorient the object  
            transform.rotation = Quaternion.LookRotation(forward, up);  
        }  
    }  
}  

3、在Cursor上添加CursorFeedback腳本組件

1） 在HoloToolkit -> Input -> Prefabs中找到HandDetectedFeedback Prefab 並拖到CursorFeedback的hand detected asset上

2） 將剛才創建的CursorBillboard拖到CursorFeedback的Feedback Parent上

CursorFeedback腳本如下（(可以直接在HoloToolKit中找到)）

// Copyright (c) Microsoft Corporation. All rights reserved.  
// Licensed under the MIT License. See LICENSE in the project root for license information.  
  
using UnityEngine;  
  
namespace HoloToolkit.Unity  
{  
    /// <summary>  
    /// CursorFeedback class takes GameObjects to give cursor feedback  
    /// to users based on different states.  
    /// </summary>  
    public class CursorFeedback : MonoBehaviour  
    {  
        [Tooltip("Drag a prefab object to display when a hand is detected.")]  
        public GameObject HandDetectedAsset;  
        private GameObject handDetectedGameObject;  
  
        [Tooltip("Drag a prefab object to parent the feedback assets.")]  
        public GameObject FeedbackParent;  
  
        void Awake()  
        {  
            if (HandDetectedAsset != null)  
            {  
                handDetectedGameObject = InstantiatePrefab(HandDetectedAsset);  
            }  
            else  
            {  
                Debug.LogError("Missing a required game object asset.  Check HandDetectedAsset is not null in editor.");  
            }  
        }  
  
        private GameObject InstantiatePrefab(GameObject inputPrefab)  
        {  
            GameObject instantiatedPrefab = null;  
  
            if (inputPrefab != null && FeedbackParent != null)  
            {  
                instantiatedPrefab = GameObject.Instantiate(inputPrefab);  
                // Assign parent to be the FeedbackParent  
                // so that feedback assets move and rotate with this parent.  
                instantiatedPrefab.transform.parent = FeedbackParent.transform;  
  
                // Set starting state of the prefab's GameObject to be inactive.  
                instantiatedPrefab.gameObject.SetActive(false);  
            }  
            else  
            {  
                Debug.LogError("Missing a required game object asset.  Check FeedbackParent is not null in editor.");  
            }  
  
            return instantiatedPrefab;  
        }  
  
        void Update()  
        {  
            UpdateHandDetectedState();  
        }  
  
        private void UpdateHandDetectedState()  
        {  
            if (handDetectedGameObject == null)  
            {  
                return;  
            }  
  
            handDetectedGameObject.SetActive(HandsManager.Instance.HandDetected);  
        }  
    }  
}  

4、運行測試

 

當手出現在Hololens視野中時，手被檢測到，在凝視射線處出現一個藍色的小手（Hololens模擬器中需要處於hold狀態才會出現藍色小手，真機上只要手舉起就可以）