unity实现双指触摸实现鼠标滚轮滚动效果，请给出示例代码

以下是Unity中实现双指触摸实现鼠标滚轮滚动效果的示例代码：

using UnityEngine;
using System.Collections;

public class TouchMouseWheel : MonoBehaviour {
    public float sensitivity = 10.0f;

    private float scrollVelocity = 0.0f;

    // Update is called once per frame
    void Update () {
        if (Input.touchCount == 2) {
            Touch touchZero = Input.GetTouch(0);
            Touch touchOne = Input.GetTouch(1);

            Vector2 touchZeroPrevPos = touchZero.position - touchZero.deltaPosition;
            Vector2 touchOnePrevPos = touchOne.position - touchOne.deltaPosition;

            float prevTouchDeltaMag = (touchZeroPrevPos - touchOnePrevPos).magnitude;
            float touchDeltaMag = (touchZero.position - touchOne.position).magnitude;

            float deltaMagnitudeDiff = prevTouchDeltaMag - touchDeltaMag;

            scrollVelocity += deltaMagnitudeDiff * sensitivity * Time.deltaTime;

            MouseScroll(scrollVelocity);
        }

        // Decrease velocity over time
        scrollVelocity = Mathf.Lerp(scrollVelocity, 0, Time.deltaTime * sensitivity);
    }

    // Simulate mouse scroll wheel
    void MouseScroll(float delta) {
        #if UNITY_EDITOR || UNITY_STANDALONE || UNITY_WEBGL
        float scrollWheelAmount = delta * 0.1f;

        // scroll mousewheel to replicate zoom effect
        if (scrollWheelAmount > 0) {
            // scroll up
            Event e = new Event();
            e.delta = new Vector2(0, 1 * scrollWheelAmount);
            e.type = EventType.ScrollWheel;
            e.mousePosition = Input.mousePosition;
            e.control = false;
            e.shift = false;
            e.alt = false;
            e.command = false;
            if (Input.GetAxis("Mouse ScrollWheel") == 0) {
                Event.current = e;
            }
            else {
                // Hack: if mouse is already scrolling, add delta to the existing scroll value
                e.delta = new Vector2(0, Input.GetAxis("Mouse ScrollWheel") + (1 * scrollWheelAmount));
                Event.current = e;
            }
            SendMessage("OnScrollWheel", SendMessageOptions.DontRequireReceiver);
        }
        else if (scrollWheelAmount < 0) {
            // scroll down
            Event e = new Event();
            e.delta = new Vector2(0, -1 * Mathf.Abs(scrollWheelAmount));
            e.type = EventType.ScrollWheel;
            e.mousePosition = Input.mousePosition;
            e.control = false;
            e.shift = false;
            e.alt = false;
            e.command = false;
            if (Input.GetAxis("Mouse ScrollWheel") == 0) {
                Event.current = e;
            }
            else {
                // Hack: if mouse is already scrolling, add delta to the existing scroll value
                e.delta = new Vector2(0, Input.GetAxis("Mouse ScrollWheel") - (1 * Mathf.Abs(scrollWheelAmount)));
                Event.current = e;
            }
            SendMessage("OnScrollWheel", SendMessageOptions.DontRequireReceiver);
        }

        #endif
    }
}

注意：该示例代码仅适用于Unity编辑器、桌面浏览器和WebGL平台，其它平台需要加以修改。