Unity中JSON序列化大尺寸多维数组的性能问题咨询

我正在Unity中学习数据序列化，尝试保存随时间变化的地形瓦片splatmaps/alphamaps。这些splatmaps/alphamaps尺寸为5125123，单份就包含超过50万个浮点数据。目前序列化16份这类数据时，耗时高达50秒，生成的JSON文件大小达到246MB。我用Newtonsoft配合自定义转换器实现，输出结果看似正常，但不确定这个耗时和文件体积是否合理，也不清楚代码有没有问题，希望能得到排查帮助。

现有序列化代码 #

private void SaveTerrainCellData(string SaveName)
{
    string saveName = $"{SaveName} - TerrainCellData";
    string filePath = (Application.persistentDataPath + "/" + saveName + ".json");
    string lines = null;
    //Debug.Log(Application.persistentDataPath);

    // Use custom converters
    var settings = new JsonSerializerSettings
    {
        Converters = new JsonConverter[] { new Vector3Converter(), new StringEnumConverter() },
        Formatting = Formatting.Indented
    };

    foreach (TerrainCellData data in this.terrainCellsData)
    {
        lines += JsonConvert.SerializeObject(data, settings);
    }

    File.WriteAllText(filePath, lines);
    //await Task.Yield();
}

数据结构定义 #

public struct TerrainCellData
{
    [SerializeField] public string TerrainName; 

    [Header("--- Weather ---")]
    public Weather Weather;
    public float MinutesSinceWeatherChange;

    [Header("--- Simulation ---")]
    public Biome Biome;
    public float WaterLevel;
    public float SunLevel;
    public int DirtPatchCount;
    public int GrassPatchCount;

    public List<Vector3> DirtAlphaMapGridID;
    public List<Vector3> GrassAlphaMapGridID;
    public Vector3 TrailingGrassPatch;
    public Vector3 TrailingDirtPatch;

    public Dictionary<ObjectName, Vector3> TrailingPlants;
    public int TrailingGrassPlantIndex;

    public float[,,] OriginalSplatmapData;
    public Dictionary<Vector3, float[,,]> AlphaMapGrid;
    public float[,,] AlphaMap;

    public void WriteData(string TerrainName,
                           Weather Weather, 
                           float MinutesSinceWeatherChange, 
                           Biome Biome, 
                           float WaterLevel, 
                           float SunLevel, 
                           int DirtPatchCount, 
                           int GrassPatchCount, 
                           List<Vector3> DirtAlphaMapGridID, 
                           List<Vector3> GrassAlphaMapGridID,
                           Vector3 TrailingGrassPatch,
                           Vector3 TrailingDirtPatch,
                           Dictionary<ObjectName, Vector3> TrailingPlants,
                           int TrailingGrassPlantIndex,
                           float[,,] OriginalSplatmapData,
                           Dictionary<Vector3, float[,,]> AlphaMapGrid,
                           float[,,] AlphaMap)
    {
        this.TerrainName = TerrainName;
        this.Weather = Weather;
        this.MinutesSinceWeatherChange = MinutesSinceWeatherChange;
        this.Biome = Biome;
        this.WaterLevel = WaterLevel;
        this.SunLevel = SunLevel;
        this.DirtPatchCount = DirtPatchCount;
        this.GrassPatchCount = GrassPatchCount;
        this.DirtAlphaMapGridID = DirtAlphaMapGridID;
        this.GrassAlphaMapGridID = GrassAlphaMapGridID;
        this.TrailingGrassPatch = TrailingGrassPatch;
        this.TrailingDirtPatch = TrailingDirtPatch;
        this.TrailingPlants = TrailingPlants;
        this.TrailingGrassPlantIndex = TrailingGrassPlantIndex;
        this.OriginalSplatmapData = OriginalSplatmapData;
        this.AlphaMapGrid = AlphaMapGrid;
        this.AlphaMap = AlphaMap;
    }
}

问题排查与优化方向 #

• 修复字符串拼接的性能浪费：当前用lines +=拼接序列化结果，每次拼接都会生成新字符串，产生大量GC开销。改用StringBuilder替代：

  StringBuilder sb = new StringBuilder();
  foreach (TerrainCellData data in this.terrainCellsData)
  {
      sb.Append(JsonConvert.SerializeObject(data, settings));
  }
  File.WriteAllText(filePath, sb.ToString());
  

• 替换JSON为二进制序列化：JSON是文本格式，存储大量浮点数据天生低效。可以改用：

  • Unity内置的二进制序列化方案（注意版本兼容性）
  • MessagePack这类高效二进制序列化库
  • 自定义二进制写入：直接将浮点数组转为字节数组写入，跳过文本转换

• 关闭JSON缩进格式：Formatting.Indented会增加文件体积和序列化时间，若不需要人工查看，改为Formatting.None可显著提升速度并减小文件大小。

• 清理冗余数据：检查TerrainCellData中的重复或可推导数据，比如OriginalSplatmapData是否需要完整保存；Dictionary<Vector3, float[,,]>中的Vector3键可转为紧凑格式（如x,y,z字符串或整数哈希），减少序列化开销。

• 异步执行避免主线程卡顿：将序列化和文件写入改为异步操作，避免阻塞游戏主线程：

  private async Task SaveTerrainCellDataAsync(string SaveName)
  {
      string saveName = $"{SaveName} - TerrainCellData";
      string filePath = Path.Combine(Application.persistentDataPath, saveName + ".json");
      StringBuilder sb = new StringBuilder();
  
      var settings = new JsonSerializerSettings
      {
          Converters = new JsonConverter[] { new Vector3Converter(), new StringEnumConverter() },
          Formatting = Formatting.None
      };
  
      foreach (TerrainCellData data in this.terrainCellsData)
      {
          sb.Append(JsonConvert.SerializeObject(data, settings));
      }
  
      await File.WriteAllTextAsync(filePath, sb.ToString());
  }
  

内容的提问来源于stack exchange，提问作者MrSig