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Unity开放世界实时GI分块烘焙策略技术详解

news 来源：原创 2025/4/29 17:33:29

一、开放世界光照挑战与分块方案

1. 超大场景光照的核心痛点

单次烘焙不可行：256km²场景的完整烘焙需数周计算时间
内存压力：单张8K光照贴图占用128MB（BC7压缩）
动态更新需求：昼夜循环、天气系统需要局部重烘焙

2. 分块策略设计

graph TB
    A[世界网格划分] --> B[9宫格加载区]
    B --> C[动态加载卸载]
    C --> D[异步烘焙队列]
    D --> E[边缘过渡处理]

分块类型	尺寸建议	光照贴图分辨率	加载半径
核心区块	500x500m	4096x4096	立即加载
邻近区块	500x500m	2048x2048	玩家移动预测
远景区块	1000x1000m	1024x1024	按需加载

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二、技术实现架构

1. 场景分块管理系统

public class WorldStreamer : MonoBehaviour {
    public Vector2Int currentChunkCoord;
    public float chunkSize = 500f;
    public int loadRadius = 2;

    void Update() {
        Vector3 playerPos = GetPlayerPosition();
        Vector2Int newCoord = GetCurrentChunkCoord(playerPos);
        
        if(newCoord != currentChunkCoord) {
            UnloadOutOfRangeChunks(newCoord);
            LoadNewChunks(newCoord);
            currentChunkCoord = newCoord;
        }
    }

    Vector2Int GetCurrentChunkCoord(Vector3 pos) {
        return new Vector2Int(
            Mathf.FloorToInt(pos.x / chunkSize),
            Mathf.FloorToInt(pos.z / chunkSize)
        );
    }
}

2. 光照数据动态加载

IEnumerator LoadLightmapData(string chunkId) {
    // 从Addressables加载光照数据
    var loadHandle = Addressables.LoadAssetAsync<LightmapData>(chunkId);
    yield return loadHandle;
    
    if(loadHandle.Status == AsyncOperationStatus.Succeeded) {
        LightmapSettings.lightmaps = LightmapSettings.lightmaps
            .Concat(new LightmapData[]{ loadHandle.Result }).ToArray();
    }
}

void UnloadLightmapData(string chunkId) {
    Addressables.Release(chunkId);
}

三、分块烘焙核心代码

1. 异步分块烘焙控制器

public class ChunkBaker : MonoBehaviour {
    Queue<ChunkTask> bakeQueue = new Queue<ChunkTask>();
    bool isBaking = false;

    public void EnqueueBake(Chunk chunk) {
        bakeQueue.Enqueue(new ChunkTask(chunk));
        if(!isBaking) StartCoroutine(ProcessBakeQueue());
    }

    IEnumerator ProcessBakeQueue() {
        isBaking = true;
        while(bakeQueue.Count > 0) {
            ChunkTask task = bakeQueue.Dequeue();
            yield return BakeChunk(task);
        }
        isBaking = false;
    }

    IEnumerator BakeChunk(ChunkTask task) {
        Lightmapping.BakeAsync(); // 开始异步烘焙
        while(Lightmapping.isRunning) {
            task.progress = Lightmapping.progress;
            yield return null;
        }
        SaveLightmapData(task.chunk);
    }
}

2. 烘焙参数动态配置

void ConfigureBakeSettings(Chunk chunk) {
    Lightmapping.lightingSettings.lightmapper = LightingSettings.Lightmapper.ProgressiveGPU;
    Lightmapping.lightingSettings.indirectResolution = GetLODResolution(chunk.lodLevel);
    Lightmapping.lightingSettings.lightmapMaxSize = GetMaxTextureSize(chunk.importance);
    Lightmapping.lightingSettings.filteringMode = LightmapFilteringMode.Auto;
}

四、边缘过渡与数据缝合

1. 光照贴图混合Shader

float4 frag(v2f i) : SV_Target {
    float4 colorA = tex2D(_MainTex, i.uv);
    float4 colorB = tex2D(_BlendTex, i.blendUV);
    
    // 基于距离的线性混合
    float blendFactor = smoothstep(_BlendStart, _BlendEnd, i.distanceToEdge);
    return lerp(colorA, colorB, blendFactor);
}

2. 数据缝合算法

Texture2D StitchLightmaps(Texture2D texA, Texture2D texB) {
    int borderSize = 16;
    Color[] pixelsA = texA.GetPixels(borderSize, 0, texA.width - borderSize*2, texA.height);
    Color[] pixelsB = texB.GetPixels(borderSize, 0, texB.width - borderSize*2, texB.height);
    
    // 混合边缘像素
    for(int i=0; i<borderSize; i++) {
        float t = (float)i / borderSize;
        pixelsA[texA.width - borderSize + i] = Color.Lerp(
            pixelsA[texA.width - borderSize + i],
            pixelsB[i],
            t
        );
    }
    
    Texture2D stitched = new Texture2D(texA.width, texA.height);
    stitched.SetPixels(pixelsA);
    stitched.Apply();
    return stitched;
}

五、性能优化方案

1. 多级缓存策略

缓存级别	存储介质	数据粒度	命中率
L0	GPU显存	当前活动区块	95%
L1	内存	邻近区块	80%
L2	SSD/NVMe	所有区块	100%

2. 动态LOD控制

float CalculateLODLevel(Vector3 playerPos, Chunk chunk) {
    float distance = Vector3.Distance(playerPos, chunk.center);
    return Mathf.Clamp01(distance / chunk.viewDistance);
}

int GetTextureResolution(float lod) {
    if(lod < 0.3f) return 4096;
    if(lod < 0.6f) return 2048;
    return 1024;
}