@authot: 白袍小道
- 转载说明那啥即可。
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( 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
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（插入：比之够着，知至目的）
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Memo of GBuffer (UE4.18)
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GBufferA : Normal(rgb), PerObjectGBufferData(a)
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GBufferB : Metallic(r), Specular(g), Roughness(b), ShadingModelID(a&0xF),
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SelectiveOutputMask(a&0xF0)
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GBufferC : BaseColor(rgb), IndirectIrradiance(a)
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GBufferD : CustomData(rgba)
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GBufferE : PrecomputedShadowFactors(rgba)
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SceneDepth
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CustomNativeDepth : depth®
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CustomStencilTexture
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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
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Dbuffer
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DBufferA : PreMultColor(rgb), ColorOpacity(a)
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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
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/
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