private void TerrainGen()   // 生成（更新）地形網(wǎng)格
    {
        // 使用了子物體網(wǎng)格的方法，而不是網(wǎng)格合并的方法

        // 因此需要首先清除所有子物體
        for (int i = 0; i < transform.childCount; i++)
        {
            Destroy(transform.GetChild(i).gameObject);
        }


        // 四叉樹計(jì)算
        // 三個(gè)buffer計(jì)算方法
        List<int> BufferA = new List<int>();
        List<int> BufferB = new List<int>();
        List<int> FinalBuffer = new List<int>();

        Vector3 ppos = player.transform.position;

        // 迭代計(jì)算
        BufferA.Add(0);             // bufferA初始化，加入根節(jié)點(diǎn)
        while (BufferA.Count != 0)  // 當(dāng)bufferA不為空時(shí)
        {
            while (BufferA.Count != 0)   // 遍歷buffera每個(gè)值
            { 
                int i = BufferA[0];
                float dist = Mathf.Sqrt(Mathf.Pow((qTree[i].begin_Pos.x + 64 * qTree[i].interval) * 5 - ppos.z, 2) + Mathf.Pow((qTree[i].begin_Pos.y + 64 * qTree[i].interval) * 5 - ppos.x, 2));   // 計(jì)算瓦片中心距離玩家位置的水平距離
                
                BufferA.Remove(i);

                if (dist >= 0.8 * 128 * qTree[i].interval * 5)   // 1表示1倍瓦片邊長(zhǎng)；128表示瓦片行列數(shù)；5時(shí)xzbias（此處其實(shí)應(yīng)該參數(shù)化）
                {
                    // 那么這張瓦片距離玩家太遠(yuǎn)，可以直接使用當(dāng)前l(fā)od，不用細(xì)化
                    FinalBuffer.Add(i);
                }
                else
                {
                    // 否則這張瓦片距離玩家很近，如果有更小的lod，應(yīng)該細(xì)化；
                    if(qTree[i].LodLeval == 0)  // 如果已經(jīng)是最細(xì)節(jié)的瓦片了，那沒辦法了，直接顯示
                    {
                        FinalBuffer.Add(i);
                    }
                    else        // 否則把它的四個(gè)更細(xì)節(jié)的子節(jié)點(diǎn)加入到待計(jì)算的b buffer
                    {
                        for(int j = 1; j <= 4; j++)
                        {
                            BufferB.Add(i * 4 + j);
                        }
                    }
                }
            }

            // 將ab buffer交換
            foreach(int i in BufferB)
            {
                BufferA.Add(i);
            }
            BufferB.Clear();
        }


        Mesh[] tiles = new Mesh[FinalBuffer.Count];

        Material mat = GetComponent<Renderer>().material;

        for (int i = 0; i < FinalBuffer.Count; i++)
        {
            tiles[i] = new Mesh();
            tiles[i].indexFormat = UnityEngine.Rendering.IndexFormat.UInt32;
            string path = @"Assets\LodMeshes\LodMesh_" + FinalBuffer[i].ToString() + ".asset";
            tiles[i] = (Mesh)AssetDatabase.LoadAssetAtPath(path, typeof(Mesh));

            GameObject theTile = new GameObject();
            theTile.transform.parent = this.transform;
            theTile.name = "lod_" + i.ToString();
            theTile.AddComponent<MeshFilter>();
            theTile.AddComponent<MeshRenderer>();
            theTile.AddComponent<Renderer>();

            theTile.GetComponent<MeshFilter>().mesh = new Mesh();
            theTile.GetComponent<MeshFilter>().mesh = tiles[i];
            theTile.GetComponent<Renderer>().material = mat;
        }


    }

    void Update()
    {
        if((int)player.transform.position.x / (64 * 5) != x_area || (int)player.transform.position.z / (64 * 5) != z_area)  // 玩家區(qū)域改變
        {
            TerrainGen();
            x_area = (int)player.transform.position.x / (64 * 5);
            z_area = (int)player.transform.position.z / (64 * 5);
        }
    }

    private void ReadQTree()
    {
        using(StreamReader RawTerrainData = new StreamReader(@"E:\Unity\MyProjects\Desert_01\Assets\TerrainTree\MyQTree.txt"))
        {
            string line;
            for (int i = 0; i < qTree.Length; i++)   // 讀取所有頂點(diǎn)   并且給原始uv數(shù)據(jù)賦值
            {
                line = RawTerrainData.ReadLine();
                string[] stringdata = line.Split(' ');

                // 讀取并寫入
                float.TryParse(stringdata[0], out qTree[i].begin_Pos.x);
                float.TryParse(stringdata[1], out qTree[i].begin_Pos.y);
                int.TryParse(stringdata[2], out qTree[i].interval);
                int.TryParse(stringdata[3], out qTree[i].LodLeval);
                float.TryParse(stringdata[4], out qTree[i].Center.x);
                float.TryParse(stringdata[5], out qTree[i].Center.y);

            }
        }
    }