Hololens开发笔记之Gaze凝视射线
凝视是HoloLens首要输入方式，形式功能类似于桌面系统的光标，用于选择操作全息对象。然而在Unity中并没有明确的Gaze API或者组件。
概念上来说，Gaze是通过用户头部两眼之间发出一条向前方的射线来实现的，射线可以识别它所碰撞的物体。在Unity中，使用Main Camera来表示用户头部的位置和朝向。准确的说，是指UnityEngine.Camera.main.transform.forward 和 UnityEngine.Camera.main.transform.position.调用Physics.RayCast 发出射线后可以得到RaycastHit结果，该结果包含了碰撞点的3D位置参数和碰撞对象。
实现Gaze的例子
void Update() { RaycastHit hitInfo; if (Physics.Raycast( Camera.main.transform.position, Camera.main.transform.forward, out hitInfo, 20.0f, Physics.DefaultRaycastLayers)) { // 如果射线成功击中物体 // hitInfo.point代表了射线碰撞的位置 // hitInfo.collider.gameObject代表了射线注视的全息对象 } }
在使用Gaze的时候，尽量避免每个物体都发出凝视射线，而是使用单例对象来管理凝视射线和其结果。
可视化凝视的具体例子
可以直接使用HoloToolkit中的GazeManager.cs脚本来实现凝视射线。
可以参考或直接使用HoloToolkit-Unity项目中的GazeManager.cs和预制的各种指针资源，包括Cursor.prefab 和 CursorWithFeedback.prefab 等。
1、添加GazeManager.cs
点击“ Create Empty” 创建一个空游戏对象，并将其命名为 Manager，为 Manager对象添加核心脚本组件GazeManager.cs
// Copyright (c) Microsoft Corporation. All rights reserved. // Licensed under the MIT License. See LICENSE in the project root for license information. using UnityEngine; using UnityEngine.VR.WSA; namespace HoloToolkit.Unity { /// <summary> /// GazeManager determines the location of the user's gaze, hit position and normals. /// </summary> public partial class GazeManager : Singleton<GazeManager> { [Tooltip("Maximum gaze distance, in meters, for calculating a hit.")] public float MaxGazeDistance = 15.0f; [Tooltip("Select the layers raycast should target.")] public LayerMask RaycastLayerMask = Physics.DefaultRaycastLayers; /// <summary> /// Physics.Raycast result is true if it hits a hologram. /// </summary> public bool Hit { get; private set; } /// <summary> /// HitInfo property gives access /// to RaycastHit public members. /// </summary> public RaycastHit HitInfo { get; private set; } /// <summary> /// Position of the intersection of the user's gaze and the holograms in the scene. /// </summary> public Vector3 Position { get; private set; } /// <summary> /// RaycastHit Normal direction. /// </summary> public Vector3 Normal { get; private set; } /// <summary> /// Object currently being focused on. /// </summary> public GameObject FocusedObject { get; private set; } [Tooltip("Checking enables SetFocusPointForFrame to set the stabilization plane.")] public bool SetStabilizationPlane = true; [Tooltip("Lerp speed when moving focus point closer.")] public float LerpStabilizationPlanePowerCloser = 4.0f; [Tooltip("Lerp speed when moving focus point farther away.")] public float LerpStabilizationPlanePowerFarther = 7.0f; private Vector3 gazeOrigin; private Vector3 gazeDirection; private float lastHitDistance = 15.0f; private void Update() { gazeOrigin = Camera.main.transform.position; gazeDirection = Camera.main.transform.forward; UpdateRaycast(); UpdateStabilizationPlane(); } /// <summary> /// Calculates the Raycast hit position and normal. /// </summary> private void UpdateRaycast() { // Get the raycast hit information from Unity's physics system. RaycastHit hitInfo; Hit = Physics.Raycast(gazeOrigin, gazeDirection, out hitInfo, MaxGazeDistance, RaycastLayerMask); GameObject oldFocusedObject = FocusedObject; // Update the HitInfo property so other classes can use this hit information. HitInfo = hitInfo; if (Hit) { // If the raycast hits a hologram, set the position and normal to match the intersection point. Position = hitInfo.point; Normal = hitInfo.normal; lastHitDistance = hitInfo.distance; FocusedObject = hitInfo.collider.gameObject; } else { // If the raycast does not hit a hologram, default the position to last hit distance in front of the user, // and the normal to face the user. Position = gazeOrigin + (gazeDirection * lastHitDistance); Normal = -gazeDirection; FocusedObject = null; } // Check if the currently hit object has changed if (oldFocusedObject != FocusedObject) { if (oldFocusedObject != null) { oldFocusedObject.SendMessage("OnGazeLeave", SendMessageOptions.DontRequireReceiver); } if (FocusedObject != null) { FocusedObject.SendMessage("OnGazeEnter", SendMessageOptions.DontRequireReceiver); } } } /// <summary> /// Adds the stabilization plane modifier if it's enabled and if it doesn't exist yet. /// </summary> private void UpdateStabilizationPlane() { // We want to use the stabilization logic. if (SetStabilizationPlane) { // Check if it exists in the scene. if (StabilizationPlaneModifier.Instance == null) { // If not, add it to us. gameObject.AddComponent<StabilizationPlaneModifier>(); } } if (StabilizationPlaneModifier.Instance) { StabilizationPlaneModifier.Instance.SetStabilizationPlane = SetStabilizationPlane; } } } }
2、创建一个新的游戏对象Cube,用来测试凝视效果
3、添加Cursor
就像PC使用鼠标来选中和交互图标一样，你可以为凝视也实现一个指针来更好的代表用户的凝视。
从 HoloToolkit/Input/Prefabs/ 目录下拖拽 Cursor Prefab 组件到场景中。这样当凝视在全息对象时，其表面会出现一个蓝色的光圈，表示当前凝视该对象，当射线离开该游戏对象时，Cursor变成一个点光源，以此来区分是否凝视游戏对象。
可以查看到Cursor中存在两个光标对象，分别是凝视在对象上及离开光息对象时分别显示的光标
CursorManager.cs
// Copyright (c) Microsoft Corporation. All rights reserved. // Licensed under the MIT License. See LICENSE in the project root for license information. using HoloToolkit.Unity; using UnityEngine; /// <summary> /// CursorManager class takes Cursor GameObjects. /// One that is on Holograms and another off Holograms. /// 1. Shows the appropriate Cursor when a Hologram is hit. /// 2. Places the appropriate Cursor at the hit position. /// 3. Matches the Cursor normal to the hit surface. /// </summary> public partial class CursorManager : Singleton<CursorManager> { //凝视射线在全息对象上时显示的光标对象 [Tooltip("Drag the Cursor object to show when it hits a hologram.")] public GameObject CursorOnHolograms; //凝视射线离开全息对象时显示的光标对象 [Tooltip("Drag the Cursor object to show when it does not hit a hologram.")] public GameObject CursorOffHolograms; [Tooltip("Distance, in meters, to offset the cursor from the collision point.")] public float DistanceFromCollision = 0.01f; void Awake() { //当未设定光标对象时直接返回 if (CursorOnHolograms == null || CursorOffHolograms == null) { return; } // Hide the Cursors to begin with. CursorOnHolograms.SetActive(false); CursorOffHolograms.SetActive(false); } void LateUpdate() { if (GazeManager.Instance == null || CursorOnHolograms == null || CursorOffHolograms == null) { return; } //当凝视射线在全息对象上及离开全息对象时，分别显示不同的光标对象，以此来进行区分 if (GazeManager.Instance.Hit) { CursorOnHolograms.SetActive(true); CursorOffHolograms.SetActive(false); } else { CursorOffHolograms.SetActive(true); CursorOnHolograms.SetActive(false); } //计算并安置光标 // Place the cursor at the calculated position. this.gameObject.transform.position = GazeManager.Instance.Position + GazeManager.Instance.Normal * DistanceFromCollision; // Orient the cursor to match the surface being gazed at. gameObject.transform.up = GazeManager.Instance.Normal; } }
4、运行测试
当凝视射线在Cube上时，出现蓝色的光圈，表示当前凝视的点在该位置
当凝视射线离开Cube时，光标显示为一个点光源
