BlueRose 3da1c138cb vault backup: 2024-02-04 19:41:22

2024-02-04 19:41:22 +08:00

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title	date	excerpt	tags	rating
Untitled	2024-02-04 12:57:56			⭐

前言

原文地址：https://www.cnblogs.com/timlly/p/15156626.html

概念

FRenderResource：是渲染线程的渲染资源基础父类，实际的数据和逻辑由子类实现。可以认为是渲染线程中承载CPU相关相关渲染的载体。
- 比如输入的顶点数据、顶点Index数据、贴图数据等。
FRHIResource：抽象了GPU侧的资源，也是众多RHI资源类型的父类。可以认为是承载显卡API相关资源的载体。
- 比如TextureSampler、TextureObject等。
FRHICommand：其父类为FRHICommandBase结构体。其含有FRHICommandBase* Next用来保存下一个Command的指针，所以存储他的结构为链表。
- 含有接口：void void ExecuteAndDestruct(FRHICommandListBase& CmdList, FRHICommandListDebugContext& DebugContext)。执行完就销毁。
- UE使用FRHICOMMAND_MACRO宏来快速定义各种RHICommand。主要功能包含：
  - 数据和资源的设置、更新、清理、转换、拷贝、回读。
  - 图元绘制。
  - Pass、SubPass、场景、ViewPort等的开始和结束事件。
  - 栅栏、等待、广播接口。
  - 光线追踪。
  - Slate、调试相关的命令。
FRHICommandList：是RHI的指令队列，用来管理、执行一组FRHICommand的对象。
- 其子类有FRHICommandListImmediate（立即执行队列）、FRHIComputeCommandList_RecursiveHazardous与TRHIComputeCommandList_RecursiveHazardous（命令列表的递归使用）
IRHICommandContext：是RHI的命令上下文接口类，定义了一组图形API相关的操作。在可以并行处理命令列表的平台上，它是一个单独的对象类。
- 主要的接口函数有：
  - 派发ComputeShader
  - 渲染查询（可见性？）
  - 相关开始/结束函数。
  - 设置数据（Viewport、GraphicsPipelineState等）
  - 设置ShadserParameter
  - 绘制图元
  - 纹理拷贝/更新
  - Raytracing
- IRHICommandContext的接口和FRHICommandList的接口高度相似且重叠。IRHICommandContext还有许多子类：
- IRHICommandContextPSOFallback：不支持真正的图形管道的RHI命令上下文。
  - FNullDynamicRHI：空实现的动态绑定RHI。
  - FOpenGLDynamicRHI：OpenGL的动态RHI。
  - FD3D11DynamicRHI：D3D11的动态RHI。
- FMetalRHICommandContext：Metal平台的命令上下文。
- FD3D12CommandContextBase：D3D12的命令上下文。
- FVulkanCommandListContext：Vulkan平台的命令队列上下文。
- FEmptyDynamicRHI：动态绑定的RHI实现的接口。
- FValidationContext：校验上下文。
IRHICommandContextContainer：IRHICommandContextContainer就是包含了IRHICommandContext对象的类型。相当于存储了一个或一组命令上下文的容器，以支持并行化地提交命令队列，只在D3D12、Metal、Vulkan等现代图形API中有实现。
- D3D12存储了FD3D12Adapter* Adapter、FD3D12CommandContext* CmdContext、 FD3D12CommandContextRedirector* CmdContextRedirector。
FDynamicRHI：FDynamicRHI是由动态绑定的RHI实现的接口，它定义的接口和CommandList、CommandContext比较相似。
- 代码详见#FDynamicRHI
FRHICommandListExecutor

FDynamicRHI

class RHI_API FDynamicRHI
{
public:
    virtual ~FDynamicRHI() {}

    virtual void Init() = 0;
    virtual void PostInit() {}
    virtual void Shutdown() = 0;

    void InitPixelFormatInfo(const TArray<uint32>& PixelFormatBlockBytesIn);

    // ---- RHI接口 ----

    // 下列接口要求FlushType: Thread safe
    virtual FSamplerStateRHIRef RHICreateSamplerState(const FSamplerStateInitializerRHI& Initializer) = 0;
    virtual FRasterizerStateRHIRef RHICreateRasterizerState(const FRasterizerStateInitializerRHI& Initializer) = 0;
    virtual FDepthStencilStateRHIRef RHICreateDepthStencilState(const FDepthStencilStateInitializerRHI& Initializer) = 0;
    virtual FBlendStateRHIRef RHICreateBlendState(const FBlendStateInitializerRHI& Initializer) = 0;

    // 下列接口要求FlushType: Wait RHI Thread
    virtual FVertexDeclarationRHIRef RHICreateVertexDeclaration(const FVertexDeclarationElementList& Elements) = 0;
    virtual FPixelShaderRHIRef RHICreatePixelShader(TArrayView<const uint8> Code, const FSHAHash& Hash) = 0;
    virtual FVertexShaderRHIRef RHICreateVertexShader(TArrayView<const uint8> Code, const FSHAHash& Hash) = 0;
    virtual FHullShaderRHIRef RHICreateHullShader(TArrayView<const uint8> Code, const FSHAHash& Hash) = 0;
    virtual FDomainShaderRHIRef RHICreateDomainShader(TArrayView<const uint8> Code, const FSHAHash& Hash) = 0;
    virtual FGeometryShaderRHIRef RHICreateGeometryShader(TArrayView<const uint8> Code, const FSHAHash& Hash) = 0;
    virtual FComputeShaderRHIRef RHICreateComputeShader(TArrayView<const uint8> Code, const FSHAHash& Hash) = 0;

     // FlushType: Must be Thread-Safe.
    virtual FRenderQueryPoolRHIRef RHICreateRenderQueryPool(ERenderQueryType QueryType, uint32 NumQueries = UINT32_MAX);
    inline FComputeFenceRHIRef RHICreateComputeFence(const FName& Name);
    
    virtual FGPUFenceRHIRef RHICreateGPUFence(const FName &Name);
    virtual void RHICreateTransition(FRHITransition* Transition, ERHIPipeline SrcPipelines, ERHIPipeline DstPipelines, ERHICreateTransitionFlags CreateFlags, TArrayView<const FRHITransitionInfo> Infos);
    virtual void RHIReleaseTransition(FRHITransition* Transition);

    // FlushType: Thread safe.    
    virtual FStagingBufferRHIRef RHICreateStagingBuffer();
    virtual void* RHILockStagingBuffer(FRHIStagingBuffer* StagingBuffer, FRHIGPUFence* Fence, uint32 Offset, uint32 SizeRHI);
    virtual void RHIUnlockStagingBuffer(FRHIStagingBuffer* StagingBuffer);
    
    // FlushType: Thread safe, but varies depending on the RHI
    virtual FBoundShaderStateRHIRef RHICreateBoundShaderState(FRHIVertexDeclaration* VertexDeclaration, FRHIVertexShader* VertexShader, FRHIHullShader* HullShader, FRHIDomainShader* DomainShader, FRHIPixelShader* PixelShader, FRHIGeometryShader* GeometryShader) = 0;
    // FlushType: Thread safe
    virtual FGraphicsPipelineStateRHIRef RHICreateGraphicsPipelineState(const FGraphicsPipelineStateInitializer& Initializer);
    
    // FlushType: Thread safe, but varies depending on the RHI
    virtual FUniformBufferRHIRef RHICreateUniformBuffer(const void* Contents, const FRHIUniformBufferLayout& Layout, EUniformBufferUsage Usage, EUniformBufferValidation Validation) = 0;
    virtual void RHIUpdateUniformBuffer(FRHIUniformBuffer* UniformBufferRHI, const void* Contents) = 0;
    
    // FlushType: Wait RHI Thread
    virtual FIndexBufferRHIRef RHICreateIndexBuffer(uint32 Stride, uint32 Size, uint32 InUsage, ERHIAccess InResourceState, FRHIResourceCreateInfo& CreateInfo) = 0;
    virtual void* RHILockIndexBuffer(FRHICommandListImmediate& RHICmdList, FRHIIndexBuffer* IndexBuffer, uint32 Offset, uint32 Size, EResourceLockMode LockMode);
    virtual void RHIUnlockIndexBuffer(FRHICommandListImmediate& RHICmdList, FRHIIndexBuffer* IndexBuffer);
    virtual void RHITransferIndexBufferUnderlyingResource(FRHIIndexBuffer* DestIndexBuffer, FRHIIndexBuffer* SrcIndexBuffer);

    // FlushType: Wait RHI Thread
    virtual FVertexBufferRHIRef RHICreateVertexBuffer(uint32 Size, uint32 InUsage, ERHIAccess InResourceState, FRHIResourceCreateInfo& CreateInfo) = 0;
    // FlushType: Flush RHI Thread
    virtual void* RHILockVertexBuffer(FRHICommandListImmediate& RHICmdList, FRHIVertexBuffer* VertexBuffer, uint32 Offset, uint32 SizeRHI, EResourceLockMode LockMode);
    virtual void RHIUnlockVertexBuffer(FRHICommandListImmediate& RHICmdList, FRHIVertexBuffer* VertexBuffer);
    // FlushType: Flush Immediate (seems dangerous)
    virtual void RHICopyVertexBuffer(FRHIVertexBuffer* SourceBuffer, FRHIVertexBuffer* DestBuffer) = 0;
    virtual void RHITransferVertexBufferUnderlyingResource(FRHIVertexBuffer* DestVertexBuffer, FRHIVertexBuffer* SrcVertexBuffer);

    // FlushType: Wait RHI Thread
    virtual FStructuredBufferRHIRef RHICreateStructuredBuffer(uint32 Stride, uint32 Size, uint32 InUsage, ERHIAccess InResourceState, FRHIResourceCreateInfo& CreateInfo) = 0;
    // FlushType: Flush RHI Thread
    virtual void* RHILockStructuredBuffer(FRHICommandListImmediate& RHICmdList, FRHIStructuredBuffer* StructuredBuffer, uint32 Offset, uint32 SizeRHI, EResourceLockMode LockMode);
    virtual void RHIUnlockStructuredBuffer(FRHICommandListImmediate& RHICmdList, FRHIStructuredBuffer* StructuredBuffer);

    // FlushType: Wait RHI Thread
    virtual FUnorderedAccessViewRHIRef RHICreateUnorderedAccessView(FRHIStructuredBuffer* StructuredBuffer, bool bUseUAVCounter, bool bAppendBuffer) = 0;
    // FlushType: Wait RHI Thread
    virtual FUnorderedAccessViewRHIRef RHICreateUnorderedAccessView(FRHITexture* Texture, uint32 MipLevel) = 0;
    // FlushType: Wait RHI Thread
    virtual FUnorderedAccessViewRHIRef RHICreateUnorderedAccessView(FRHITexture* Texture, uint32 MipLevel, uint8 Format);

    (......)

    // RHI帧更新，须从主线程调用，FlushType: Thread safe
    virtual void RHITick(float DeltaTime) = 0;
    // 阻塞CPU直到GPU执行完成变成空闲. FlushType: Flush Immediate (seems wrong)
    virtual void RHIBlockUntilGPUIdle() = 0;
    // 开始当前帧，并确保GPU正在积极地工作 FlushType: Flush Immediate (copied from RHIBlockUntilGPUIdle)
    virtual void RHISubmitCommandsAndFlushGPU() {};

    // 通知RHI准备暂停它.
    virtual void RHIBeginSuspendRendering() {};
    // 暂停RHI渲染并将控制权交给系统的操作, FlushType: Thread safe
    virtual void RHISuspendRendering() {};
    // 继续RHI渲染, FlushType: Thread safe
    virtual void RHIResumeRendering() {};
    // FlushType: Flush Immediate
    virtual bool RHIIsRenderingSuspended() { return false; };

    // FlushType: called from render thread when RHI thread is flushed 
    // 仅在FRHIResource::FlushPendingDeletes内的延迟删除之前每帧调用.
    virtual void RHIPerFrameRHIFlushComplete();

    // 执行命令队列, FlushType: Wait RHI Thread
    virtual void RHIExecuteCommandList(FRHICommandList* CmdList) = 0;

    // FlushType: Flush RHI Thread
    virtual void* RHIGetNativeDevice() = 0;
    // FlushType: Flush RHI Thread
    virtual void* RHIGetNativeInstance() = 0;

    // 获取命令上下文. FlushType: Thread safe
    virtual IRHICommandContext* RHIGetDefaultContext() = 0;
    // 获取计算上下文. FlushType: Thread safe
    virtual IRHIComputeContext* RHIGetDefaultAsyncComputeContext();

    // FlushType: Thread safe
    virtual class IRHICommandContextContainer* RHIGetCommandContextContainer(int32 Index, int32 Num) = 0;

    // 直接由渲染线程调用的接口, 以优化RHI调用.
    virtual FVertexBufferRHIRef CreateAndLockVertexBuffer_RenderThread(class FRHICommandListImmediate& RHICmdList, uint32 Size, uint32 InUsage, ERHIAccess InResourceState, FRHIResourceCreateInfo& CreateInfo, void*& OutDataBuffer);
    virtual FIndexBufferRHIRef CreateAndLockIndexBuffer_RenderThread(class FRHICommandListImmediate& RHICmdList, uint32 Stride, uint32 Size, uint32 InUsage, ERHIAccess InResourceState, FRHIResourceCreateInfo& CreateInfo, void*& OutDataBuffer);
    
    (......)

    // Buffer Lock/Unlock
    virtual void* LockVertexBuffer_BottomOfPipe(class FRHICommandListImmediate& RHICmdList, ...);
    virtual void* LockIndexBuffer_BottomOfPipe(class FRHICommandListImmediate& RHICmdList, ...);
    
    (......)
};

以上只显示了部分接口，其中部分接口要求从渲染线程调用，部分须从游戏线程调用。大多数接口在被调用前需刷新指定类型的命令，比如：

class RHI_API FDynamicRHI
{
    // FlushType: Wait RHI Thread
    void RHIExecuteCommandList(FRHICommandList* CmdList);

    // FlushType: Flush Immediate
    void RHIBlockUntilGPUIdle();

    // FlushType: Thread safe 
    void RHITick(float DeltaTime);
};

可以在FRHICommandListImmediate的ExecuteCommandList()、BlockUntilGPUIdle()、Tick() 看到调用。

需要注意的是，传统图形API（D3D11、OpenGL）除了继承FDynamicRHI，还需要继承IRHICommandContextPSOFallback，因为需要借助后者的接口处理PSO的数据和行为，以保证传统和现代API对PSO的一致处理行为。也正因为此，现代图形API（D3D12、Vulkan、Metal）不需要继承IRHICommandContext的任何继承体系的类型，单单直接继承FDynamicRHI就可以处理RHI层的所有数据和操作。既然现代图形API（D3D12、Vulkan、Metal）的DynamicRHI没有继承IRHICommandContext的任何继承体系的类型，那么它们是如何实现FDynamicRHI::RHIGetDefaultContext的接口？下面以FD3D12DynamicRHI为例：

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前言

概念

FDynamicRHI

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