要达到吸附效果则需要每个拼图上挂载碰撞体

达到整张图片的替换效果需要选中所有拼图部件把材质球拖上去

、

制作材料球

脚本挂载到随便一个空物体上

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PinTu : MonoBehaviour
{
    // 记录有没有拼图被选中
    private GameObject selectedObject;

    // 拼图预制体
    GameObject[] dragObj;
    // 记录拼图应该放的点
    GameObject[] dropObj;
    // Start is called before the first frame updateq
    void Start()
    {
        dragObj = GameObject.FindGameObjectsWithTag("drag");
        dropObj = GameObject.FindGameObjectsWithTag("drop");

        foreach (var item in dragObj)
        {
            item.transform.position = new Vector3(Random.Range(-0.2f, 0.3f), 0.815f, Random.Range(-0.1f,0.4f));
        }
    }

    // Update is called once per frame
    void Update()
    {
        // 如果按下了鼠标左键
        if (Input.GetMouseButtonDown(0))
        {
            // 选中的物体为空
            if (selectedObject == null)
            {
                // 存储的射线信息
                RaycastHit hit = CastRay();
                // 碰到的物体有碰撞器
                if (hit.collider != null)
                {
                    // 如果标签不是drag直接返回
                    if (!hit.collider.CompareTag("drag"))
                    {
                        return;
                    }
                    // 碰到的物体标签是--drag,为selectedObject赋值
                    selectedObject = hit.collider.gameObject;
                    // 设置鼠标光标不可见
                    Cursor.visible = false;
                }
            }

            // 选中物体之后，再按一下鼠标左键---放下物体
            else
            {
                // 记录鼠标点击的点
                Vector3 position = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.WorldToScreenPoint(selectedObject.transform.position).z);
                Vector3 worldPosition = Camera.main.ScreenToWorldPoint(position);

                #region  吸附
                //遍历每个放置点，找到和鼠标点击最近的点
                Vector3 tmpdrop = Vector3.zero;
                float minDistance = 10.0f;
                foreach (var item in dropObj)
                {
                    if (Vector3.Distance(item.transform.position, worldPosition) <= minDistance)
                    {
                        minDistance = Vector3.Distance(item.transform.position, worldPosition);
                        tmpdrop = item.transform.position;
                    }
                }
                // 如果最小距离小于---限定值，说明在拼图位置上，就赋值，否则就是鼠标位置
                if (minDistance < 0.04f)
                {
                    // 赋值
                    selectedObject.transform.position = tmpdrop + new Vector3(0, 0.003f, 0);

                }
                else
                {
                    selectedObject.transform.position = worldPosition;
                }
                #endregion
                //selectedObject.transform.position = worldPosition;
                selectedObject = null;
                Cursor.visible = true;
            }
        }



        // 如果selectedObject不为空，说明点击到了物体，物体跟随鼠标移动
        if (selectedObject != null)
        {
            // position存储的是鼠标的x,y坐标，自身的z坐标---屏幕坐标
            Vector3 position = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.WorldToScreenPoint(selectedObject.transform.position).z);
            // 将屏幕坐标，转换为世界坐标
            Vector3 worldPosition = Camera.main.ScreenToWorldPoint(position);
            // 为选中的物体赋值--这里的y是固定的0.25
            selectedObject.transform.position = new Vector3(worldPosition.x, 0.811f, worldPosition.z);

            // 按下鼠标的右键，旋转
            if (Input.GetMouseButtonDown(1))
            {
                selectedObject.transform.rotation = Quaternion.Euler(new Vector3(
                    selectedObject.transform.rotation.eulerAngles.x,
                    selectedObject.transform.rotation.eulerAngles.y + 90f,
                    selectedObject.transform.rotation.eulerAngles.z));
            }
        }
    }
    // 返回射线碰撞信息
    private RaycastHit CastRay()
    {
        // 射线最远的点
        Vector3 screenMousePosFar = new Vector3(
            Input.mousePosition.x,
            Input.mousePosition.y,
            Camera.main.farClipPlane);
        // 射线最近的点
        Vector3 screenMousePosNear = new Vector3(
            Input.mousePosition.x,
            Input.mousePosition.y,
            Camera.main.nearClipPlane);
        Vector3 worldMousePosFar = Camera.main.ScreenToWorldPoint(screenMousePosFar);
        Vector3 worldMousePosNear = Camera.main.ScreenToWorldPoint(screenMousePosNear);
        RaycastHit hit;
        Physics.Raycast(worldMousePosNear, worldMousePosFar - worldMousePosNear, out hit);

        return hit;
    }
}