基础力反馈教程

本教程将指导您创建一个基础触觉模拟，同时包含刚度和阻尼，用于模拟与静态物体（例如球体）接触时的物理特性。 完成本教程后，您将拥有一个模拟程序，可以感受到球体的存在，并调整其刚度和阻尼属性，以获得不同的触觉体验。

简介

本教程的核心挑战是开发一个函数，用于计算与同时具有 刚度 和 阻尼 的球体接触时产生的力。 在此语境中，刚度的作用类似于弹簧，压缩得越多，产生的力就越大。 另一方面，阻尼表示物体对运动的阻力，物体移动得越快，所受阻力越大。

场景设置

首先，按照 入门指南 中的说明设置 Haptic Rig，并确保 Haptic Origin 的位置、旋转和缩放分别设置为 (0, 0, 0) 和 (1, 1, 1)。

然后，创建一个名为 Sphere 的球体，并设置以下属性：

• 位置：(0, 0, -0.1)（约位于设备前方 10 厘米处）
• 缩放：(0.2, 0.2, 0.2)（对应直径为 20 厘米的球体）

力反馈脚本

为 Sphere 游戏对象添加一个新的 C# 脚本，命名为 SphereForceFeedback.cs。 该脚本将在与球体接触时计算施加到 Inverse3 光标上的力，同时考虑刚度和阻尼。 使用以下属性初始化脚本：

[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;

仅当光标穿透球体时才应进行力计算，以模拟触碰具有特定刚度和阻尼的实体物体时的感觉。 ForceCalculation 方法将负责此项计算，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);
}

在 Awake 方法中，初始化 _ballPosition、_ballRadius 和 _cursorRadius，以设置场景数据：

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

    _cursorRadius = inverse3.Cursor.Radius;
}

private void Awake()
{
    SaveSceneData();
}

请确保分别在 OnEnable 和 OnDisable 方法中注册和注销 OnDeviceStateChanged 回调，以便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

握住 Inverse3 光标时，进入播放模式，尝试触碰球体。 您应当能够感受到球体的存在，并通过 Unity 检查器调整其刚度和阻尼属性，从而获得与虚拟物体交互的真实触感。

源文件

本示例的完整场景及所有相关文件，均可从 Unity 包管理器中的 Tutorials 示例导入。

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);
        }
    }
}