輪轉(zhuǎn)圖是游戲中較為常見(jiàn)的功能，在我們制作一些場(chǎng)景選關(guān)或者是做一些選擇類似的UI時(shí)，我們會(huì)覺(jué)得想制作一種3D效果的選擇方式，3D輪轉(zhuǎn)圖往往就是最恰當(dāng)?shù)囊环N

實(shí)現(xiàn)原理：
????利用父物體生成子物體選項(xiàng)，子物體利用x軸上的間距和 最中心靠前的物體最大顯示(縮放最大)，兩側(cè)物體逐漸變小(縮放逐漸變小)的原理制造視覺(jué)差，從而形成3D效果，之后利用DragHandler事件制作拖動(dòng)旋轉(zhuǎn)即可

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using DG.Tweening;

public class Chart2d : MonoBehaviour,IDragHandler,IEndDragHandler
{
    public Image prefab;//預(yù)制體
    public int num;//個(gè)數(shù)
    public float spacing;//間距

    float c;//周長(zhǎng)
    float r;//半徑
    float ang;//每個(gè)角的弧度
    float dis = 0;//拖動(dòng)的距離
    float max = 1;//縮放最大值
    float min = 0.5f;//縮放最小值
    float cutSpeed = 100;//速度

    List<GameObject> list = new List<GameObject>();//查找預(yù)制體用集合
    List<Transform> sorts = new List<Transform>();//排序用集合
    // Start is called before the first frame update
    void Start()
    {
        //周長(zhǎng) = （寬 + 間距）* 個(gè)數(shù)
        c = (prefab.rectTransform.rect.width + spacing) * num;
        //半徑 = 周長(zhǎng)/圓的弧度
        r = c / (2 * Mathf.PI);
        //每個(gè)角的弧度 = 圓的弧度/個(gè)數(shù)
        ang = (2 * Mathf.PI) / num;
        Move();
    }

    public void Move()
    {
        //移動(dòng)的弧度 = 拖動(dòng)的距離/半徑
        float moveang = dis / r;
        for (int i = 0; i < num; i++)
        {
            float x = Mathf.Sin(i * ang + moveang) * r;
            float z = Mathf.Cos(i * ang + moveang) * r;
            //計(jì)算縮放比值，例如：半徑是1，最近是-1最遠(yuǎn)是1，所以要算直徑的比值，將最近和最遠(yuǎn)都+1，得出0到2的值，用它與直徑2作比較
            float p = (z + r) / (2 * r);
            //進(jìn)大遠(yuǎn)小需要反過(guò)來(lái)，0是離你比較進(jìn)的距離
            p = 1 - p;
            //用比值計(jì)算縮放 區(qū)間 * 比例 + 最小值
            float scale = (max - min) * p + min;
            //沒(méi)有就創(chuàng)建
            if (list.Count <= i)
            {
                GameObject image = Instantiate(prefab.gameObject, transform);
                image.name = i.ToString();
                list.Add(image);
                sorts.Add(image.transform);
            }
            //設(shè)置位置
            list[i].transform.localPosition = Vector3.right * x;
            //設(shè)置縮放
            list[i].transform.localScale = Vector3.one * scale;
        }
        //按縮放排序
        sorts.Sort((a, b) =>
        {
            if (a.localScale.x < b.localScale.x)
            {
                return -1;
            }
            else if (a.localScale.x == b.localScale.x)
            {
                return 0;
            }
            else
            {
                return 1;
            }
        });
        //根據(jù)排序設(shè)置渲染順序
        for (int i = 0; i < sorts.Count; i++)
        {
            sorts[i].SetSiblingIndex(i);
        }
    }


    // Update is called once per frame
    void Update()
    {
        
    }
    //拖動(dòng)
    public void OnDrag(PointerEventData eventData)
    {
        //橫向拖動(dòng)距離
        dis -= eventData.delta.x;
        Move();
    }
    //拖動(dòng)停止計(jì)算慣性
    public void OnEndDrag(PointerEventData eventData)
    {
        //停止時(shí)的速度
        float startspeed = eventData.delta.x;
        float endspeed = 0;
        //計(jì)算停止的時(shí)間
        float time = Mathf.Abs(startspeed) / cutSpeed;
        DOTween.To((float a) =>
        {
            dis -= a;
            Move();
        }, startspeed, endspeed, time).OnComplete(() =>
        {
            //停止后對(duì)齊最大的
            Align(list.IndexOf(sorts[num - 1].gameObject));
        });
    }
    //對(duì)齊指定下標(biāo)
    public void Align(int n)
    {
        //當(dāng)前的下標(biāo)
        int i = list.IndexOf(sorts[num - 1].gameObject);
        //計(jì)算與指定下標(biāo)相隔多少個(gè)
        int s = i - n;
        int s2 = num - Mathf.Abs(s);
        s2 = s > 0 ? -s2 : s2;
        int s3 = Mathf.Abs(s) < Mathf.Abs(s2) ? s : s2;
        //需要轉(zhuǎn)動(dòng)的弧度
        float moveAng = Mathf.Asin(sorts[num - 1].localPosition.x / r) + s3 * ang;
        //需要轉(zhuǎn)動(dòng)的距離
        float moveDis = moveAng * r;
        //需要轉(zhuǎn)動(dòng)的時(shí)間
        float time = Mathf.Abs(moveDis) / cutSpeed;
        DOTween.To((float a) =>
        {
            dis = a;
            Move();
        }, dis, dis + moveDis, time).OnComplete(() =>
        {
            //對(duì)齊后調(diào)用預(yù)制體上的函數(shù)
            //sorts[num - 1].GetComponent<xx>().xx();
        });
    }
}