（原）Unreal渲染相关的缓冲区 及其 自定义代码几种抓取

@authot: 白袍小道

 

• 转载说明那啥即可。
• 
• (图片和本文无关，嘿嘿，坑一下）

   
   

   
   

• 以下为Unreal4.18版本中对GPUBuffer部分的分析结果
• （插入：比之够着，知至目的）

   
   

• Memo of GBuffer (UE4.18)

   
   

  • GBufferA : Normal(rgb), PerObjectGBufferData(a)

     
     

  • GBufferB : Metallic(r), Specular(g), Roughness(b), ShadingModelID(a&0xF),

     
     

  • SelectiveOutputMask(a&0xF0)

     
     

  • GBufferC : BaseColor(rgb), IndirectIrradiance(a)

     
     

  • GBufferD : CustomData(rgba)

     
     

  • GBufferE : PrecomputedShadowFactors(rgba)

     
     

  • SceneDepth

     
     

  • CustomNativeDepth : depth®

     
     

  • CustomStencilTexture

     
     

  • GBufferVelocity : rgba

    补充说明：注意源码中对这一块的对齐处理，线程，访问方式的处理

     
     

• Dbuffer

   
   

  • DBufferA : PreMultColor(rgb), ColorOpacity(a)

     
     

  • DBufferB : PreMulWorldNormal(rgb), NormalOpacity(a)

     
     

  • DBufferC : PreMulRoughness(r ), RoughnessOpacity(g)

   
   

  （一）、DeferredShadingRender中对Buffer的处理

  从调式和RenderDoc可以详细看到过程，这里就不做详细说明

   
   

  

  结果：

  

   
   

  (二），代码抓取

  结局：

  https://twitter.com/i/status/1096091562642001920

  

  这里主要用两种方式去获取，一种是通过Fmemory,一种直接用Unreal提供CopyShareMip

  具体如下：

  

   
   

  以下为全部代码：

   
   

  DynamicAccessGBufferRenderTarget.h：

  //////////////////这里就没有按照Buff处理做分装了，直接怼的（嘿嘿）

  #pragma once

  #include <memory>

  #include "Engine/Texture2D.h"

  #include "Object.h"

  #include "DynamicAccessGBufferRenderTarget.generated.h"

   
   

  UENUM(BlueprintType)                //"BlueprintType" is essential to include

  enum class EDZShowGbuffer : uint8

  {

  VE_GDZSHOWBUFFERA         UMETA(DisplayName = "ShowGBuffA"),

  VE_GDZSHOWBUFFERB         UMETA(DisplayName = "ShowGBuffB"),

  VE_GDZSHOWBUFFERC        UMETA(DisplayName = "ShowGBuffC"),

  VE_GDZSHOWBUFFERD        UMETA(DisplayName = "ShowGBuffD"),

  VE_GDZSHOWBUFFERE        UMETA(DisplayName = "ShowGBuffE"),

  };

   
   

  UENUM(BlueprintType)                //"BlueprintType" is essential to include

  enum class EDZCOPYGbufferType : uint8

  {

  VE_GDZSHOWGBUFFER_COPYMIP         UMETA(DisplayName = "COPY_Mip"),

  VE_GDZSHOWBUFFERR_COPYMEMO         UMETA(DisplayName = "COPY_Memory"),

  VE_GDZSHOWBUFFERC_CPUARRAY        UMETA(DisplayName = "COPY_MemoryForWhile"),

  };

   
   

  USTRUCT()

  struct FCommitRenderData

  {

  GENERATED_BODY()

  public:

  EDZCOPYGbufferType ECOPYBuffType;

  EDZShowGbuffer EShowBuff;

  UTextureRenderTarget2D* mTextureTarget;

  EPixelFormat format;

  int32 canvasWidth = 512;

  int32 canvasHeight = 512;

  bool isGetGBufferData = false;

  };

   
   

  UCLASS(Blueprintable, BlueprintType)

  class DZRENDERSTUDIOPLUGIN_API UDynamicAccessGBufferRenderTarget : public UObject

  {

  GENERATED_BODY()

   
   

  public:

  UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = DynamicAccessGBufferRenderTarget)

  EDZCOPYGbufferType ECOPYBuffType;

   
   

  UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = DynamicAccessGBufferRenderTarget)

  EDZShowGbuffer EShowBuff;

   
   

  UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = DynamicAccessGBufferRenderTarget)

  UTextureRenderTarget2D* mTextureTarget;

   
   

  UFUNCTION(BlueprintCallable, Category = DynamicAccessGBufferRenderTarget)

  void InitializeTexture(UTextureRenderTarget2D* pTextureTarget,EDZShowGbuffer pEShowBuff, EDZCOPYGbufferType pECOPYBuffType);

   
   

  UFUNCTION(BlueprintCallable, Category = DynamicAccessGBufferRenderTarget)

  void CaputerGBuffer();

   
   

  UFUNCTION(BlueprintCallable, Category = DynamicAccessGBufferRenderTarget)

  void ClearTexture();

   
   

  UDynamicAccessGBufferRenderTarget();

  ~UDynamicAccessGBufferRenderTarget();

   
   

  static void CaputerGBufer_Rebuild_RenderThread(FCommitRenderData* pRenderData);

  static void CaputerGBuffer_RenderThread(FCommitRenderData* pRenderData);

   
   

  static void Copy_TextureRHI(FRHICommandListImmediate& RHICmdList, FRHITexture2D* pDesc, FRHITexture2D* pSrc);

  static void Copy_MemoryRHI(FRHICommandListImmediate& RHICmdList, FRHITexture2D* pDesc, FRHITexture2D* pSrc);

  static void Copy_CPUArrayRHI();

   
   

  private:

  EPixelFormat format;

  UPROPERTY()

  FCommitRenderData CatchRenderData;

   
   

  UPROPERTY()

  bool isRebulidRenderTargetSuccess = false;

  };

   
   

   
   

   
   

  DynamicAccessGBufferRenderTarget.cpp

  /**

  * 1、这里步骤基本为先得到当前Buffer的大小，刷新RT目标的数据。并在基础属性变化时* 候再次刷新

  * 2、抓取数据（由于BUFF在Render管线处理时候有获取和释放的处理也是为了能及时释* 放，所以手动加1，

  * 当然成对的写法在DepthRender, Slate等都可以看到，这非常好。

  * 3、CopyShare或者利用FMemory::Memcpy(但拷贝前需要加锁，完成后还需要解锁,所* * 以你懂的

  **/

   
   

  #include "DynamicAccessGBufferRenderTarget.h"

  #include "private/PostProcess/SceneRenderTargets.h"

  #include "Engine.h"

  #include "RHICommandList.h"

   
   

   
   

   
   

   
   

  UDynamicAccessGBufferRenderTarget::UDynamicAccessGBufferRenderTarget()

  {

   
   

  }

   
   

  UDynamicAccessGBufferRenderTarget::~UDynamicAccessGBufferRenderTarget()

  {

   
   

  }

   
   

  void UDynamicAccessGBufferRenderTarget::InitializeTexture(UTextureRenderTarget2D* pTextureTarget

  , EDZShowGbuffer pEShowBuff, EDZCOPYGbufferType pECOPYBuffType)

  {

  if (mTextureTarget != pTextureTarget || EShowBuff != pEShowBuff || ECOPYBuffType != pECOPYBuffType)

  {

  mTextureTarget = pTextureTarget;

  EShowBuff = pEShowBuff;

  ECOPYBuffType = pECOPYBuffType;

  isRebulidRenderTargetSuccess = false;

  }

   
   

  }

   
   

  void UDynamicAccessGBufferRenderTarget::ClearTexture()

  {

   
   

  }

   
   

   
   

  void UDynamicAccessGBufferRenderTarget::CaputerGBuffer()

  {

  if (!CatchRenderData.isGetGBufferData)

  {

  isRebulidRenderTargetSuccess = false;

  CatchRenderData.EShowBuff = EShowBuff;

  CatchRenderData.ECOPYBuffType = ECOPYBuffType;

  CatchRenderData.mTextureTarget = mTextureTarget;

  ENQUEUE_UNIQUE_RENDER_COMMAND_ONEPARAMETER(

  DZRenderSutioBP_AccessGBufferRenderTarget_init,

  FCommitRenderData*, RenderData, &CatchRenderData,

  {

  UDynamicAccessGBufferRenderTarget::CaputerGBufer_Rebuild_RenderThread(RenderData);

  }

  );

  }

  else

  {

  if (!isRebulidRenderTargetSuccess)

  {

  if (IsInGameThread())

  {

  mTextureTarget->InitCustomFormat(CatchRenderData.canvasWidth, CatchRenderData.canvasHeight, CatchRenderData.format, false);

  mTextureTarget->ForceRebuildPlatformData();

  }

  isRebulidRenderTargetSuccess = true;

  }

  else

  {

  CatchRenderData.EShowBuff = EShowBuff;

  CatchRenderData.ECOPYBuffType = ECOPYBuffType;

  CatchRenderData.mTextureTarget = mTextureTarget;

  ENQUEUE_UNIQUE_RENDER_COMMAND_ONEPARAMETER(

  DZRenderSutioBP_InterceptSceneGBufferToRenderTarget,

  FCommitRenderData*, RenderData, &CatchRenderData,

  {

  UDynamicAccessGBufferRenderTarget::CaputerGBuffer_RenderThread(RenderData);

  }

  );

  }

  }

   
   

  }

   
   

  void UDynamicAccessGBufferRenderTarget::CaputerGBufer_Rebuild_RenderThread(FCommitRenderData* pRenderData)

  {

  FRHICommandListImmediate& RHICmdList = GRHICommandList.GetImmediateCommandList();

  //计数加一避免Render完成后直接清空了GBuffer,但会慢一帧，你猜

  FSceneRenderTargets::Get(RHICmdList).AdjustGBufferRefCount(RHICmdList, 1);

  FSceneRenderTargets& SceneContext = FSceneRenderTargets::Get(RHICmdList);

  if (SceneContext.GBufferA)

  {

  FTexture2DRHIRef vTextTarget;

  switch (pRenderData->EShowBuff)

  {

  case EDZShowGbuffer::VE_GDZSHOWBUFFERA:

  vTextTarget = SceneContext.GetGBufferATexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERB:

  vTextTarget = SceneContext.GetGBufferBTexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERC:

  vTextTarget = SceneContext.GetGBufferCTexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERD:

  vTextTarget = SceneContext.GetGBufferDTexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERE:

  vTextTarget = SceneContext.GetGBufferETexture();

  break;

  default:

  vTextTarget = SceneContext.GetGBufferATexture();

  break;

  }

   

  pRenderData->format = vTextTarget->GetFormat();

  pRenderData->canvasWidth = vTextTarget->GetSizeX();

  pRenderData->canvasHeight = vTextTarget->GetSizeY();

  pRenderData->isGetGBufferData = true;

  }

  FSceneRenderTargets::Get(RHICmdList).AdjustGBufferRefCount(RHICmdList, -1);

  }

   
   

  void UDynamicAccessGBufferRenderTarget::CaputerGBuffer_RenderThread(FCommitRenderData* pRenderData)

  {

  FRHICommandListImmediate& RHICmdList = GRHICommandList.GetImmediateCommandList();

  //计数加一避免Render完成后直接清空了GBuffer,但会慢一帧，你猜

  FSceneRenderTargets::Get(RHICmdList).AdjustGBufferRefCount(RHICmdList, 1);

  FSceneRenderTargets& SceneContext = FSceneRenderTargets::Get(RHICmdList);

  if (SceneContext.GBufferA && pRenderData->mTextureTarget != nullptr)

  {

  FTexture2DRHIRef vTextTarget;

  switch (pRenderData->EShowBuff)

  {

  case EDZShowGbuffer::VE_GDZSHOWBUFFERA:

  vTextTarget = SceneContext.GetGBufferATexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERB:

  vTextTarget = SceneContext.GetGBufferBTexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERC:

  vTextTarget = SceneContext.GetGBufferCTexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERD:

  vTextTarget = SceneContext.GetGBufferDTexture();

  break;

  case EDZShowGbuffer::VE_GDZSHOWBUFFERE:

  vTextTarget = SceneContext.GetGBufferETexture();

  break;

  break;

  default:

  vTextTarget = SceneContext.GetGBufferATexture();

  break;

  }

  pRenderData->format = vTextTarget->GetFormat();

  if (pRenderData->canvasWidth != vTextTarget->GetSizeX())

  {

  pRenderData->isGetGBufferData = false;

  return;

  }

  FTextureReferenceRHIRef vTexRHIRef = pRenderData->mTextureTarget->TextureReference.TextureReferenceRHI;

  FRHITexture* vRTTexture = vTexRHIRef->GetTextureReference()->GetReferencedTexture();

  FRHITexture2D* vtex = (FRHITexture2D*)vRTTexture;

  if (vtex == nullptr)

  {

  return;

  }

  switch (pRenderData->ECOPYBuffType)

  {

  case EDZCOPYGbufferType::VE_GDZSHOWGBUFFER_COPYMIP:

  UDynamicAccessGBufferRenderTarget::Copy_TextureRHI(RHICmdList,vtex, vTextTarget);

  break;

  case EDZCOPYGbufferType::VE_GDZSHOWBUFFERR_COPYMEMO:

  UDynamicAccessGBufferRenderTarget::Copy_MemoryRHI(RHICmdList, vtex, vTextTarget);

  break;

  case EDZCOPYGbufferType::VE_GDZSHOWBUFFERC_CPUARRAY:

  UDynamicAccessGBufferRenderTarget::Copy_CPUArrayRHI();

  break;

  default:

  break;

  }

  RHICmdList.CopySharedMips(vtex, vTextTarget);

  }

  //移除

  FSceneRenderTargets::Get(RHICmdList).AdjustGBufferRefCount(RHICmdList, -1);

  }

   
   

  //利用SharedMip的共享方式在这里会快一些

  //扩展方式

  void UDynamicAccessGBufferRenderTarget::Copy_TextureRHI(FRHICommandListImmediate& RHICmdList,FRHITexture2D* pDesc,FRHITexture2D* pSrc)

  {

  RHICmdList.CopySharedMips(pDesc, pSrc);

  }

   
   

  //内存CPY，但需要锁住，这样就会让另外的渲染不能访问，会造成掉帧率。

  void UDynamicAccessGBufferRenderTarget::Copy_MemoryRHI(FRHICommandListImmediate& RHICmdList, FRHITexture2D* pDesc, FRHITexture2D* pSrc)

  {

  uint32 Lolstrid = 0;

  void * UAVRenderTargetData = RHILockTexture2D(pDesc, 0, RLM_WriteOnly, Lolstrid, true);

  void * UAVCSData = RHILockTexture2D(pSrc, 0, RLM_ReadOnly, Lolstrid, true);

  FMemory::Memcpy(UAVRenderTargetData, UAVCSData, GPixelFormats[pSrc->GetFormat()].BlockBytes * pSrc->GetSizeX() * pSrc->GetSizeY());

  RHICmdList.UnlockTexture2D(pDesc, 0, false);

  RHICmdList.UnlockTexture2D(pSrc, 0, false);

  }

   
   

  void UDynamicAccessGBufferRenderTarget::Copy_CPUArrayRHI()

  {

   
   

  }

   
   

  蓝图和资源部分

  1、RT （1个对应一个结果）

  2、一个UI材质（用于做一些额外效果）

  3、一个UI蓝图（就是调用代码和绑定资源，用C++也可以，偷懒下）

  

  RT赋予

  

  BP部分

  UI_ShowCapResul_Child：

  

   
   

  除了一些我们自己做的方式和LitMode中调试方式

   
   

  还以通过像素检查器进行分析和查看

  

   
   

  题外：

  1、Create Custom GBUFFER ：http://www.catalinzima.com/xna/tutorials/deferred-rendering-in-xna/creating-the-g-buffer/

   
   

  2、Buffer,RT ,Pipeline

  https://medium.com/@lordned/unreal-engine-4-rendering-part-4-the-deferred-shading-pipeline-389fc0175789

   
   

  3、https://en.wikipedia.org/wiki/Deferred_shading

   
   

  4、高效的GPU GBUFFER管理：http://www.klayge.org/2015/05/25/%E9%AB%98%E6%95%88gpu-buffer%E7%AE%A1%E7%90%86%E4%B9%8Btransient-buffer/