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TomicyoTomicyo
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add post about struct serializer
add post about custom rendering component in UE4 update streaming POST
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‎8.misc/cpp_msics.md‎

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# C++ Actor模式
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* 什么是Actor模型
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* 分布式
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CAF
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# ECS框架
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* 游戏框架
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# 微软Concurency Runtime并行库
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# enkiTS
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* 开源的任务调度库
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* 建立任务依赖

‎8.misc/images/streaming_manager_notify_detach.png‎

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‎8.misc/images/streaming_manager_notify_primitive.png‎

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‎8.misc/images/ue4_streaming_call_stack.png‎

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‎8.misc/ue4_custom_rendering_component.md‎

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# UE4自定义渲染组件
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---
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## SceneComponent
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UE场景最基础组件
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---
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## PrimitiveComponent
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图元组件包含渲染，也包含物理碰撞，导航网格，资源串流等逻辑，是UE最常见组件
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``` cpp
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class UXXXComponent : public UPrimitiveComponent
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{
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public:
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// 视锥裁剪相关
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FBoxSphereBounds CalcBounds(const FTransform& LocalToWorld) const override;
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// 渲染代理
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FPrimitiveSceneProxy* CreateSceneProxy() override;
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virtual void GetUsedMaterials(TArray<UMaterialInterface *>& OutMaterials, bool bGetDebugMaterials /* = false */) const;
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// Streaming相关接口
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/** Build the data to compute accuracte StreaminTexture data. */
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virtual bool BuildTextureStreamingData(ETextureStreamingBuildType BuildType, EMaterialQualityLevel::Type QualityLevel, ERHIFeatureLevel::Type FeatureLevel, TSet<FGuid>& DependentResources) override;
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/** Get the StreaminTexture data include mesh, 此接口加入待流送的纹理、Mesh、关联的包围盒 & TexelFactor */
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virtual void GetStreamingRenderAssetInfo(FStreamingTextureLevelContext& LevelContext, TArray<FStreamingRenderAssetPrimitiveInfo>& OutStreamingRenderAssets) const override;
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};
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class FXXXSceneProxy : public FPrimitiveSceneProxy
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{
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public:
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// View可见性接口实现，【关键】决定在MainView，Reflection Capture是否可见
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FPrimitiveViewRelevance GetViewRelevance(const FSceneView* View) const override;
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// 获取动态渲染元素
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void GetDynamicMeshElements(
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const TArray<const FSceneView*>& Views,
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const FSceneViewFamily& ViewFamily,
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uint32 VisibilityMap,
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FMeshElementCollector& Collector) const override;
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// 获取静态渲染元素
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void DrawStaticElements(FStaticPrimitiveDrawInterface* PDI) override;
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// 获取光追元素
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void GetDynamicRayTracingInstances(FRayTracingMaterialGatheringContext& Context,
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TArray<FRayTracingInstance>& OutRayTracingInstances) override;
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};
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```
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> UE4资源流送调用堆栈
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![](images/ue4_streaming_call_stack.png)
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> Primitive RenderState(Create_Concurrent)
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![](images/streaming_manager_notify_primitive.png)
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![](images/streaming_manager_notify_detach.png)
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> IStreamingManager，如果Component下的RenderState发生变化，需要显式调用`IStreamingManager::Get().NotifyPrimitiveUpdated(this)`
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如何继承**UStreamableRenderAsset** ？
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* Streamable RenderAsset仅支持单一文件单一LOD流送
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如何流送单一资源文件，多物件流送？
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* BulkData、RangeIO
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* 自己继承IStreamingManager（^_^），单独管理
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### Bulk data的使用
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---
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``` cpp
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class IAsyncReadRequest;
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typedef TFunction<void(bool bWasCancelled, IAsyncReadRequest*)> FAsyncFileCallBack;
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class FByteBulkData
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{
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public:
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GetFileName();
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FBulkDataIORequest*
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CreateStreamingRequest(
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EAsyncIOPriorityAndFlags Priority,
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FAsyncFileCallBack* CompleteCallback,
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uint8* UserSuppliedMemory) const;
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FBulkDataIORequest*
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CreateStreamingRequest(
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int64 OffsetInBulkData, int64 BytesToRead,
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EAsyncIOPriorityAndFlags Priority,
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FAsyncFileCallBack* CompleteCallback,
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uint8* UserSuppliedMemory) const;
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};
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```
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---
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## AnyComponent
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UE4中单一逻辑组件可用，类似体积云、虚拟纹理等，单独管理，单独渲染（无排序），需修改场景管理、渲染器渲染过程、材质Shader相关逻辑。
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---
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## MeshBatch & MeshCommand & RayTracingInstance
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MeshBatch描述**单一VertexBuffer**不同Section的材质渲染，但实际只支持一个材质，但不同的MeshSection（**MeshBatchElement**）的特定材质参数可能不一样。
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MeshPassProcessor会将MeshBatch转换成对应MeshCommand。

‎8.misc/ue4_custom_struct_serializer.md‎

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# UE4自定义结构体序列化
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> 疑问：像TMap这样的复杂结构是如何序列化的呢
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先看看TStructOpsTypeTraitsBase2这个类
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----
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## TStructOpsTypeTraitsBase2
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```cpp
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USTRUCT()
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struct FXXX
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{
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bool Serialize(FArchive& Ar);
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};
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template<>
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struct TStructOpsTypeTraits<FXXX> : public TStructOpsTypeTraitsBase2<FXXX>
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{
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enum
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{
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WithSerializer = true
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};
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};
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```
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再看看更基础的**FVector**，序列化的代码位于***UObject/Property.cpp***
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> 使用StructOpsTypeTraits的代码位于***UObject/Class.h***
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UScriptStruct （代理类） 记录 T 反射信息 ICppStructOps

‎8.misc/ue4_file_ops.md‎

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UE4 IO & Package介绍
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===
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* UPackage & FLinker & FArchive
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* BulkData
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* PlatformFile
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* NetworkFileSystem
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## 基础IO文件操作
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---
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- FileHelper (最简单的文件操作方式)
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``` cpp
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#include "Misc/FileHelper.h"
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FFileHelper::BufferToString( FString& Result, const uint8* Buffer, int32 Size )
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FFileHelper::LoadFileToArray(TArray<uint8>& Result, const TCHAR* Filename, uint32 Flags = 0);
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FFileHelper::LoadFileToString( FString& Result, const TCHAR* Filename, EHashOptions VerifyFlags = EHashOptions::None, uint32 ReadFlags = 0 );
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```
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- PlatformFile
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- IFileManager
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``` cpp
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#include "HAL/FileManager.h"
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class IFileManager
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{
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public:
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static IFileManager& Get();
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FArchive* CreateFileReader( const TCHAR* Filename, uint32 ReadFlags=0 );
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FArchive* CreateFileWriter( const TCHAR* Filename, uint32 WriteFlags=0 );
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bool DirectoryExists( const TCHAR* InDirectory );
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FDateTime GetAccessTimeStamp( const TCHAR* Filename );
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};
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```
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- FPlatformFileManager 最复杂的文件读取方式
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``` cpp
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#include "HAL/PlatformFileManager.h"
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class FPlatformFileManager {
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public:
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static FPlatformFileManager& Get();
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// 创建
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IPlatformFile* GetPlatformFile( const TCHAR* Name );
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IPlatformFile& GetPlatformFile();
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};
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// 平台文件抽象类
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class IPlatformFile {
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public:
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void InitializeNewAsyncIO();
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IFileHandle* OpenRead(const TCHAR* Filename, bool bAllowWrite = false);
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IFileHandle* OpenReadNoBuffering(const TCHAR* Filename, bool bAllowWrite = false);
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IFileHandle* OpenWrite(const TCHAR* Filename, bool bAppend = false, bool bAllowRead = false);
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IAsyncReadFileHandle* OpenAsyncRead(const TCHAR* Filename);
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// 内存映射文件
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IMappedFileHandle* OpenMapped(const TCHAR* Filename);
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IMappedFileHandle* AllocateMapped(const TCHAR* Filename, int64 Size);
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bool CopyDirectoryTree(const TCHAR* DestinationDirectory, const TCHAR* Source, bool bOverwriteAllExisting);
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};
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```
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- BulkData 读取
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``` cpp
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// BulkData (Size > 16K)
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class IAsyncReadRequest;
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typedef TFunction<void(bool bWasCancelled, IAsyncReadRequest*)> FAsyncFileCallBack;
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class FByteBulkData
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{
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public:
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GetFileName();
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FBulkDataIORequest*
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CreateStreamingRequest(
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EAsyncIOPriorityAndFlags Priority,
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FAsyncFileCallBack* CompleteCallback,
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uint8* UserSuppliedMemory) const;
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FBulkDataIORequest*
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CreateStreamingRequest(
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int64 OffsetInBulkData, int64 BytesToRead,
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EAsyncIOPriorityAndFlags Priority,
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FAsyncFileCallBack* CompleteCallback,
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uint8* UserSuppliedMemory) const;
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};
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// 异步文件读取
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IAsyncReadFileHandle* IORequestHandle = FPlatformFileManager::Get().GetPlatformFile().OpenAsyncRead(*Filename);
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check(IORequestHandle); // this generally cannot fail because it is async
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if (IORequestHandle == nullptr)
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{
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return nullptr;
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}
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const int64 OffsetInFile = GetBulkDataOffsetInFile() + OffsetInBulkData;
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IAsyncReadRequest* ReadRequest = IORequestHandle->ReadRequest(OffsetInFile, BytesToRead, Priority, CompleteCallback, UserSuppliedMemory);
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if (ReadRequest != nullptr)
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{
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return new FBulkDataIORequest(IORequestHandle, ReadRequest, BytesToRead);
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}
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else
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{
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delete IORequestHandle;
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return nullptr;
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}
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bool FBulkDataIORequest::PollCompletion() const
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{
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return ReadRequest->PollCompletion();
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}
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bool FBulkDataIORequest::WaitCompletion(float TimeLimitSeconds) const
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{
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return ReadRequest->WaitCompletion(TimeLimitSeconds);
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}
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uint8* FBulkDataIORequest::GetReadResults() const
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{
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return ReadRequest->GetReadResults();
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}
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```
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- MemoryMapping File（内存映射文件）
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```cpp
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check(!FPlatformProperties::GetMemoryMappingAlignment() || IsAligned(BulkDataOffsetInFile, FPlatformProperties::GetMemoryMappingAlignment()));
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bWasMapped = BulkData.MapFile(*Filename, BulkDataOffsetInFile, GetBulkDataSize());
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bool FUntypedBulkData::FAllocatedPtr::MapFile(const TCHAR *InFilename, int64 Offset, int64 Size)
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{
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check(!MappedHandle && !MappedRegion); // It doesn't make sense to do this twice, but if need be, not hard to do
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MappedHandle = FPlatformFileManager::Get().GetPlatformFile().OpenMapped(InFilename);
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if (!MappedHandle)
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{
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return false;
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}
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MappedRegion = MappedHandle->MapRegion(Offset, Size, true); //@todo we really don't want to hit the disk here to bring it into memory
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if (!MappedRegion)
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{
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delete MappedHandle;
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MappedHandle = nullptr;
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return false;
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}
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check(Size == MappedRegion->GetMappedSize());
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Ptr = (void*)(MappedRegion->GetMappedPtr()); //@todo mapped files should probably be const-correct
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check(IsAligned(Ptr, FPlatformProperties::GetMemoryMappingAlignment()));
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bAllocated = true;
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return true;
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}
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void FUntypedBulkData::FAllocatedPtr::UnmapFile()
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{
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if (MappedRegion || MappedHandle)
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{
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delete MappedRegion;
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delete MappedHandle;
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MappedRegion = nullptr;
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MappedHandle = nullptr;
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Ptr = nullptr; // make sure we don't try to free this pointer
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}
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}
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```
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- FArchive
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```cpp
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class FArchive {
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public:
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FString GetArchiveName() const;
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FLinker* GetLinker();
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int64 TotalSize();
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bool AtEnd();
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void Seek(int64 InPos);
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int64 Tell();
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void Flush();
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void Serialize(void* V, int64 Length);
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FArchive& ByteOrderSerialize(void* V, int32 Length);
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bool SetCompressionMap(TArray<struct FCompressedChunk>* CompressedChunks, ECompressionFlags CompressionFlags);
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void SerializeCompressed(void* V, int64 Length, FName CompressionFormat, ECompressionFlags Flags=COMPRESS_NoFlags, bool bTreatBufferAsFileReader=false);
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void AttachBulkData(UObject* Owner, FUntypedBulkData* BulkData);
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void DetachBulkData(FUntypedBulkData* BulkData, bool bEnsureBulkDataIsLoaded);
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//版本管理
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int32 UE4Ver() const;
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FEngineVersionBase EngineVer() const;
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int32 CustomVer(const struct FGuid& Key) const;
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void UsingCustomVersion(const struct FGuid& Guid);
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private:
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// 自定义版本
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mutable FCustomVersionContainer* CustomVersionContainer = nullptr;
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};
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```
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---
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## UPackage结构
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## DirectStorage
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- Queue IO Request
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``` cpp
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QueueReuest(DestMemoryAddress, FileName)
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QueueSignal(Fence)
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```

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