1、node interface

using UnityEngine;
namespace FrameDT
{
    public interface INode
    {
        Bounds m_bound { get; set; }
        Node Inside(Bounds bound);
        void InsidePush(Bounds bound);

        void AddObject(GameObject obj);
        void RemoveObject(GameObject obj);

        void DrawBound();
    }
}

2、node

using System.Collections.Generic;
using UnityEngine;

namespace FrameDT
{
    public class Node : INode
    {
        public Bounds m_bound { get; set; }

        private int m_depth;
        private Node m_belong;
        private Node[] m_childNode;
        private List<GameObject> m_objects;

        public Node(Bounds bound, int depth, Node belong)
        {
            m_belong = belong;

            m_bound = bound;
            m_depth = depth;

            Insert();
        }

        public void Insert()
        {
            if (m_depth < TreeNode.MaxDepth)
            {
                if (m_childNode == null)
                {
                    CreateChild();
                }
                else
                {
                    for (int i = 0; i < m_childNode.Length; ++i)
                    {
                        Node item = m_childNode[i];
                        item.Insert();
                    }
                }
            }
            else
            {
                m_objects = new List<GameObject>(16);
            }
        }

        public Node Inside(Bounds bound)
        {
            Node node = null;
            if (m_childNode != null)
            {
                for (int i = 0; i < m_childNode.Length; ++i)
                {
                    Node item = m_childNode[i];
                    if (item.m_bound.Intersects(bound))
                    {
                        Node child = item.Inside(bound);
                        if (child != null)
                        {
                            node = item.Inside(bound);
                            break;
                        }
                        else
                        {
                            node = item;
                            break;
                        }
                    }
                }
            }

            return node;
        }

        public void InsidePush(Bounds bound)
        {
            if (m_childNode != null)
            {
                for (int i = 0; i < m_childNode.Length; ++i)
                {
                    if (m_childNode[i].m_bound.Intersects(bound))
                    {
                        m_childNode[i].InsidePush(bound);
                    }
                }
            }

            if(m_depth == TreeNode.MaxDepth)
            {
                TreeObjManager.GetInstance().curNodes.Add(this);
            }
        }

        public void AddObject(GameObject obj)
        {
            if(m_objects != null)
            {
                m_objects.Add(obj);
            }
            else
            {
                Debug.LogError("Container Error!");
            }
        }

        public void RemoveObject(GameObject obj)
        {
            if (m_objects != null)
            {
                if(m_objects.Contains(obj))
                {
                    m_objects.Remove(obj);
                }
            }
            else
            {
                Debug.LogError("Container Error!");
            }
        }

        private void CreateChild()
        {
            m_childNode = new Node[TreeNode.NodeCount];
            int index = 0;
            if (m_childNode.Length == 4)
            {
                for (int x = -1; x <= 1; x += 2)
                {
                    for (int z = -1; z <= 1; z += 2)
                    {
                        Vector3 centerOffset = new Vector3(m_bound.size.x / 4 * x, 0, m_bound.size.z / 4 * z);
                        Vector3 cSize = new Vector3(m_bound.size.x / 2, m_bound.size.y, m_bound.size.z / 2);
                        Bounds cBound = new Bounds(m_bound.center + centerOffset, cSize);
                        m_childNode[index++] = new Node(cBound, m_depth + 1, this);
                    }
                }
            }
            else
            {
                for (int x = -1; x <= 1; x += 2)
                {
                    for (int y = -1; y <= 1; y += 2)
                    {
                        for (int z = -1; z <= 1; z += 2)
                        {
                            Vector3 centerOffset = new Vector3(m_bound.size.x / 4 * x, m_bound.size.y / 4 * y, m_bound.size.z / 4 * z);
                            Vector3 cSize = new Vector3(m_bound.size.x / 2, m_bound.size.y / 2, m_bound.size.z / 2);
                            Bounds cBound = new Bounds(m_bound.center + centerOffset, cSize);
                            m_childNode[index++] = new Node(cBound, m_depth + 1, this);
                        }
                    }
                }
            }
        }


        public Color m_color = Color.green;
        public void DrawBound()
        {
            Gizmos.color = m_color;
            Gizmos.DrawWireCube(m_bound.center, m_bound.size);

            if (m_childNode != null)
            {
                for (int i = 0; i < m_childNode.Length; ++i)
                {
                    m_childNode[i].DrawBound();
                }
            }
        }
    }
}

3、tree node

using System.Collections.Generic;
using UnityEngine;

namespace FrameDT
{
    public class TreeNode : INode
    {
        public static int MaxDepth;
        public static int NodeCount;

        public Bounds m_bound { get; set; }
        private Node m_root;
         
        public TreeNode(Bounds bound, int maxDepth, bool QuadTree)
        {
            MaxDepth = maxDepth;
            NodeCount = QuadTree ? 4 : 8;

            m_bound = bound;
            m_root = new Node(bound, 0, null);
        }

        /// <summary>
        /// 查找一个node
        /// </summary>
        public Node Inside(Bounds bound)
        {
            return m_root.Inside(bound);
        }

        /// <summary>
        /// 查找范围内的node
        /// </summary>
        public void InsidePush(Bounds bound)
        {
            m_root.InsidePush(bound);
        }

        /// <summary>
        /// 碰撞体积添加
        /// </summary>
        public void AddObject(GameObject obj)
        {
            Bounds bound = obj.GetComponent<Collider>().bounds;
            Node node = m_root.Inside(bound);
            node?.AddObject(obj);
        }

        /// <summary>
        /// 碰撞体积移除
        /// </summary>
        public void RemoveObject(GameObject obj)
        {
            Bounds bound = obj.GetComponent<Collider>().bounds;
            Node node = m_root.Inside(bound);
            node?.RemoveObject(obj);
        }

        public void DrawBound()
        {
            m_root.DrawBound();
        }
    }
}

4、测试类

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

/// <summary>
/// 四叉树管理类
/// </summary>
public class TreeObjManager : SingleMonoBase<TreeObjManager>
{
    public Bounds bounds;//当前树的大小

    public int depth;//树的深度
    public bool QuadTree;//四叉树or八叉树

    private TreeNode tree;

    //test data
    public Node curNode;
    public GameObject curCube;

    public List<Node> curNodes = new List<Node>();

    protected override void Awake()
    {
        tree = new TreeNode(bounds, depth, QuadTree);
    }

    protected override void Update()
    {
        if (Input.GetKeyDown(KeyCode.F10))
        {
            if (curCube != null) return;

            Vector3 pos = new Vector3(Random.Range(-(int)bounds.size.x / 2, (int)bounds.size.x / 2),
                Random.Range(-(int)bounds.size.y / 2, (int)bounds.size.y / 2),
                Random.Range(-(int)bounds.size.z / 2, (int)bounds.size.z / 2));

            //查找
            curNode = tree.Inside(new Bounds(pos, Vector3.zero));

            //添加
            curCube = GameObject.CreatePrimitive(PrimitiveType.Cube);
            curCube.transform.position = pos;
            curCube.transform.localScale = Vector3.one * 1;
            curNode.AddObject(curCube);
            curNode.m_color = Color.red;
        }
        else if(Input.GetKeyDown(KeyCode.F11))
        {
            //删除
            curNode.RemoveObject(curCube);
            curNode.m_color = Color.green;
            Destroy(curCube);
            curCube = null;
        }
        else if (Input.GetKeyDown(KeyCode.F12))
        {
            Vector3 pos = new Vector3(Random.Range(-(int)bounds.size.x / 2, (int)bounds.size.x / 2),
                Random.Range(-(int)bounds.size.y / 2, (int)bounds.size.y / 2),
                Random.Range(-(int)bounds.size.z / 2, (int)bounds.size.z / 2));

            //查找范围
            var obj = GameObject.CreatePrimitive(PrimitiveType.Cube);
            obj.transform.position = pos;
            obj.transform.localScale = Vector3.one * 30;
            curNodes.Clear();
            tree.InsidePush(new Bounds(pos, Vector3.one * 30));
            Debug.Log("child node num = " + curNodes.Count);
            for (int index = 0; index < curNodes.Count; index++)
            {
                if (curNodes[index] != null) curNodes[index].m_color = Color.blue;
            }
        }
    }

    private void OnDrawGizmos()
    {
        if (tree != null)
        {
            tree.DrawBound();
        }
        else
        {
            Gizmos.color = Color.green;
            Gizmos.DrawWireCube(bounds.center, bounds.size);
        }
    }
}