大概整理了一下StreamingLevel相关的流程

更新StreamingLevel状态

• World::Tick中的InternalUpdateStreamingState
  • UWorld::ProcessLevelStreamingVolumes(FVector* OverrideViewLocation) 遍历所有LevelStreamingObject然后对不同的LevelStreaming设置对应的状态
  • UWorldComposition::UpdateStreamingState() UWorldComposition::EvaluateWorldOriginLocation(*const* FVector& ViewLocation)
    • UWorldComposition::UpdateStreamingStateCinematic(*const* FVector* InLocations, int32 Num) 类似于UpdateStreamingState，如果需要在摄像模式下加载所有tile就会全部加载
    • UWorldComposition::UpdateStreamingState(*const* FVector* InLocations, int32 Num) UWorldComposition::GetDistanceVisibleLevels 获取实际的可见与不可见的Level UWorldComposition::CommitTileStreamingState(UWorld* PersistentWorld, int32 TileIdx, *bool* bShouldBeLoaded, *bool* bShouldBeVisible, *bool* bShouldBlock, int32 LODIdx) 提交实际状态
  • WorldSubsystem->UpdateStreamingState 各个世界子系统的更新 UWorldPartitionSubsystem::UpdateStreamingState ULevelInstanceSubsystem::UpdateStreamingState

等待Streaming完成

• UEngine::BlockTillLevelStreamingCompleted
  • UWorld::BlockTillLevelStreamingCompleted
    • UWorld::UpdateLevelStreaming()
      • FStreamingLevelPrivateAccessor::UpdateStreamingState 更新Streaming状态
        • ULevelStreaming::UpdateStreamingState 根据当前状态更新
          • ECurrentState::MakingVisible
            • UWorld::AddToWorld 增量更新组件
              • ULevel::IncrementalUpdateComponents ULevel::IncrementalRegisterComponents ULevel::IncrementalRunConstructionScripts
              ULevel::InitializeNetworkActors 初始化网络Actor ULevel::RouteActorInitialize 调度Actor初始化 广播Level可视化事件、Level改变事件
            ULevelStreaming::DiscardPendingUnloadLevel FScene::OnLevelAddedToWorld 更新场景几何信息
          • ECurrentState::MakingInvisible FScene::OnLevelRemovedFromWorld 更新场景几何信息 UWorld::RemoveFromWorld 增量反注册组件，增量调度Endplay，释放渲染相关资源
          • ECurrentState::Loading: 等待就行
          • ECurrentState::Unloaded:
            • 目标：ETargetState::LoadedNotVisible:
              • **ULevelStreaming::RequestLevel 这里进入加载流程 这里会切换到Loading状态或者LoadFiled**
                • 回调：ULevelStreaming::AsyncLevelLoadComplete Level状态设置为ECurrentState::LoadedNotVisible ULevelStreaming::PrepareLoadedLevel 广播给各个StreamingManager 处理需要加载到另一个包的情况 处理取消以及失败的情况
            • 目标：ETargetState::UnloadedAndRemoved: UWorld::RemoveStreamingLevel
          • ECurrentState::LoadedNotVisible:
            • 目标：ETargetState::LoadedVisible: 切换到ECurrentState::MakingVisible;
            • 目标：ETargetState::Unloaded: ULevelStreaming::DiscardPendingUnloadLevel ULevelStreaming::ClearLoadedLevel ULevelStreaming::DiscardPendingUnloadLevel
            • 目标：ETargetState::LoadedNotVisible: ULevelStreaming::DiscardPendingUnloadLevel
          • ECurrentState::LoadedVisible:
            • 目标：ETargetState::LoadedNotVisible: 状态直接切换到ECurrentState::MakingInvisible;
            • 目标：ETargetState::LoadedVisible: ULevelStreaming::RequestLevel
          • ECurrentState::FailedToLoad: 返回失败
      • FStreamingLevelPrivateAccessor::DetermineTargetState 确定更新之后的状态
        • ULevelStreaming::DetermineTargetState() 根据返回的当前状态决定目标状态

UE5中的变化

主要流程没有变化，UE5额外支持了Per Actor Per File。