基本力反馈教程

本教程将指导您创建一个包含刚度和阻尼的基本触觉模拟，模拟与球体等静态物体接触的物理特性。 本教程结束时，您将获得一个模拟，可以感受球体的存在，并调整其硬度和阻尼属性，获得不同的触觉体验。

导言

本教程的核心挑战是开发一个函数，能够计算与具有刚度和阻尼的球体接触时产生的力。 在这种情况下，刚度的作用就像弹簧一样，越压缩产生的力越大。 而阻尼则代表物体的运动阻力，移动速度越快，阻力越大。

场景设置

首先，按照以下步骤设置触觉装备 快速入门指南确保 触觉起源的位置、旋转和缩放设置为 (0, 0, 0) 和 (1, 1, 1) 分别是

然后，创建一个名为 Sphere 具有以下特性

• 职位： (0, 0, -0.1) (设备前方约 10 厘米处）。
• 规模： (0.2, 0.2, 0.2) (相当于一个直径 20 厘米的球体）

力反馈脚本

添加一个新的 C# 脚本到 球体 名为 SphereForceFeedback.cs. 该脚本将计算 Inverse3 光标与球体接触时所受的力，同时考虑刚度和阻尼。 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;

只有当光标穿透球体时，力的计算才会发生，从而模拟触摸具有确定刚度和阻尼的实物的感觉。 力的计算 ForceCalculation 方法将负责这一工作，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(Inverse3 device)
{
    // Calculate the ball force
    var force = ForceCalculation(device.LocalPosition, device.LocalVelocity,
        _cursorRadius, _ballPosition, _ballRadius);

    device.CursorSetLocalForce(force);
}

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

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

    _cursorRadius = inverse3.Cursor.Model.transform.lossyScale.x / 2f;
}

private void Awake()
{
    SaveSceneData();
}

确保注册和取消注册 OnDeviceStateChanged 中的回调 OnEnable 和 OnDisable 方法，以正确处理交互过程中的力反馈：

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

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

游戏体验

按住 Inverse3 光标，进入 "播放 "模式并尝试触摸球体。 您应该能够感受到球体的存在，并通过 Unity 检查器操作其刚度和阻尼属性，从而获得与虚拟对象进行交互的真实感。

源文件

本示例的完整场景和所有相关文件均可从 Unity 软件包管理器中的教程示例中导入。

SphereForceFeedback.cs

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

using Haply.Inverse.Unity;
using UnityEngine;

namespace Haply.Samples.Tutorials._2_BasicForceFeedback
{
    public class SphereForceFeedback : MonoBehaviour
    {
        // must assign in inspector
        public Inverse3 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.Model.transform.lossyScale.x / 2f;
        }

        /// <summary>
        /// Saves the initial scene data cache.
        /// </summary>
        private void Awake()
        {
            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;
        }

        /// <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="device">The Inverse3 device instance.</param>
        private void OnDeviceStateChanged(Inverse3 device)
        {
            // Calculate the ball force
            var force = ForceCalculation(device.LocalPosition, device.LocalVelocity,
                _cursorRadius, _ballPosition, _ballRadius);

            device.CursorSetLocalForce(force);
        }
    }
}