基本力觉反馈教程

在本教程中，为了再现与球体等静态物体接触时的物理特性，我们将创建一个同时包含刚度和阻尼的基本力觉模拟。 完成本教程后，您将制作出一个能够感知球体存在，并根据不同的力觉体验调整刚度和阻尼特性的模拟。

前言

本教程的核心任务是开发一个函数，用于计算与同时具有刚度和阻尼特性的球体接触时产生的力。 在此背景下，刚度起着类似弹簧的作用，压缩得越厉害，产生的力就越大。 另一方面，阻尼代表了物体运动所受到的阻力，移动得越快，产生的阻力就越大。

场景设置

入门指南请按照说明设置 Haptic Rig。此时，触觉起源 位置、旋转和缩放分别 (0, 0, 0)、(1, 1, 1) 请确认已设置为。

接下来，具有以下属性的 Sphere 创建一个名为……的球体。

• 职位： (0, 0, -0.1)（距设备前方约10厘米）
• 规模： (0.2, 0.2, 0.2)（相当于直径20厘米的球体）

力反馈脚本

球体 在 GameObject 上，SphereForceFeedback.cs 添加一个名为“Inverse3 ”的新 C# 脚本。 该脚本会计算球体与光标接触时作用于光标上的力，同时考虑刚度和阻尼。 使用以下属性初始化该脚本：

[SerializeField]
private Inverse3 inverse3;

[Range(0, 800)]
public float stiffness = 300f;
[Range(0, 3)]
public float damping = 1f;

private Vector3 _ballPosition;
private float _ballRadius;
private float _cursorRadius;

仅当光标进入球体内部时才需要进行力计算。这样可以再现触碰具有既定刚度和阻尼的物理对象时的触感。 ForceCalculation 该方法负责处理此操作，并同时考虑光标的位置和速度：

private Vector3 ForceCalculation(Vector3 cursorPosition, Vector3 cursorVelocity, float cursorRadius,
    Vector3 otherPosition, float otherRadius)
{
    var force = Vector3.zero;

    var distanceVector = cursorPosition - otherPosition;
    var distance = distanceVector.magnitude;
    var penetration = otherRadius + cursorRadius - distance;

    if (penetration > 0)
    {
        // Normalize the distance vector to get the direction of the force
        var normal = distanceVector.normalized;

        // Calculate the force based on penetration
        force = normal * penetration * stiffness;

        // Apply damping based on the cursor velocity
        force -= cursorVelocity * damping;
    }

    return force;
}

private void OnDeviceStateChanged(object sender, Inverse3EventArgs args)
{
    var inverse3 = args.DeviceController;
    // Calculate the ball force
    var force = ForceCalculation(inverse3.CursorLocalPosition, inverse3.CursorLocalVelocity,
        _cursorRadius, _ballPosition, _ballRadius);

    inverse3.SetCursorLocalForce(force);
}

Awake 在该方法中，为了设置场景数据 _ballPosition、_ballRadius、_cursorRadius 初始化：

private void SaveSceneData()
{
    var t = transform;
    _ballPosition = t.position;
    _ballRadius = t.lossyScale.x / 2f;

    _cursorRadius = inverse3.Cursor.Radius;
}

private void Awake()
{
    SaveSceneData();
}

OnEnable 方法与 OnDisable 在各个方法中 OnDeviceStateChanged 请注册和取消注册回调，并在交互过程中正确处理力反馈：

protected void OnEnable()
{
    inverse3.DeviceStateChanged += OnDeviceStateChanged;
}

protected void OnDisable()
{
    inverse3.DeviceStateChanged -= OnDeviceStateChanged;
}

游戏体验

Inverse3 请按住光标，进入“播放模式”，然后尝试触摸球体。 您可以感知到球体的存在，并可通过 Unity 的“检查器”调整其刚度和阻尼特性。这样，您就能切身感受到与虚拟对象的交互。

源文件

该示例的完整场景及相关文件均可从 Unity 的“包管理器”中的“Tutorials”示例中导入。

SphereForceFeedback.cs

/*
 * Copyright 2024 Haply Robotics Inc. All rights reserved.
 */

using Haply.Inverse.DeviceControllers;
using Haply.Inverse.DeviceData;
using UnityEngine;

namespace Haply.Samples.Tutorials._2_BasicForceFeedback
{
    public class SphereForceFeedback : MonoBehaviour
    {
        public Inverse3Controller inverse3;

        [Range(0, 800)]
        // Stiffness of the force feedback.
        public float stiffness = 300f;

        [Range(0, 3)]
        public float damping = 1f;

        private Vector3 _ballPosition;
        private float _ballRadius;
        private float _cursorRadius;

        /// <summary>
        /// Stores the cursor and sphere transform data for access by the haptic thread.
        /// </summary>
        private void SaveSceneData()
        {
            var t = transform;
            _ballPosition = t.position;
            _ballRadius = t.lossyScale.x / 2f;

            _cursorRadius = inverse3.Cursor.Radius;
        }

        /// <summary>
        /// Saves the initial scene data cache.
        /// </summary>
        private void Awake()
        {
            inverse3 ??= FindObjectOfType<Inverse3Controller>();
            inverse3.Ready.AddListener((device, args) => SaveSceneData());
        }

        /// <summary>
        /// Subscribes to the DeviceStateChanged event.
        /// </summary>
        private void OnEnable()
        {
            inverse3.DeviceStateChanged += OnDeviceStateChanged;
        }

        /// <summary>
        /// Unsubscribes from the DeviceStateChanged event.
        /// </summary>
        private void OnDisable()
        {
            inverse3.DeviceStateChanged -= OnDeviceStateChanged;
            inverse3.Release();
        }

        /// <summary>
        /// Calculates the force based on the cursor's position and another sphere position.
        /// </summary>
        /// <param name="cursorPosition">The position of the cursor.</param>
        /// <param name="cursorVelocity">The velocity of the cursor.</param>
        /// <param name="cursorRadius">The radius of the cursor.</param>
        /// <param name="otherPosition">The position of the other sphere (e.g., ball).</param>
        /// <param name="otherRadius">The radius of the other sphere.</param>
        /// <returns>The calculated force vector.</returns>
        private Vector3 ForceCalculation(Vector3 cursorPosition, Vector3 cursorVelocity, float cursorRadius,
            Vector3 otherPosition, float otherRadius)
        {
            var force = Vector3.zero;

            var distanceVector = cursorPosition - otherPosition;
            var distance = distanceVector.magnitude;
            var penetration = otherRadius + cursorRadius - distance;

            if (penetration > 0)
            {
                // Normalize the distance vector to get the direction of the force
                var normal = distanceVector.normalized;

                // Calculate the force based on penetration
                force = normal * penetration * stiffness;

                // Apply damping based on the cursor velocity
                force -= cursorVelocity * damping;
            }

            return force;
        }

        /// <summary>
        /// Event handler that calculates and send the force to the device when the cursor's position changes.
        /// </summary>
        /// <param name="sender">The Inverse3 data object.</param>
        /// <param name="args">The event arguments containing the device data.</param>
        private void OnDeviceStateChanged(object sender, Inverse3EventArgs args)
        {
            var inverse3 = args.DeviceController;
            // Calculate the ball force
            var force = ForceCalculation(inverse3.CursorLocalPosition, inverse3.CursorLocalVelocity,
                _cursorRadius, _ballPosition, _ballRadius);

            inverse3.SetCursorLocalForce(force);
        }
    }
}