UE5 插件版本 - PS添加PostProcess Pass
在之前的章节，一直都是改源码的去添加后期Pass，每次改源码，编译源码，时间很长，且还要同步给公司同事拉引擎库，十分麻烦，有没有简单一点的？
当然有，PostProcessing.cpp给我们暴露了拓展接口，利用插件对其进行注册，即可在PostProcessing.cpp的下列阶段触发执行
让我们开始吧！
for (const TSharedRef<ISceneViewExtension>& ViewExtension : View.Family->ViewExtensions) { for (int32 SceneViewPassId = 0; SceneViewPassId < FirstAfterPass; SceneViewPassId++) { const ISceneViewExtension::EPostProcessingPass SceneViewPass = static_cast<ISceneViewExtension::EPostProcessingPass>(SceneViewPassId); const bool bIsEnabled = (SceneViewPass == ISceneViewExtension::EPostProcessingPass::ReplacingTonemapper) ? PassSequence.IsEnabled(EPass::Tonemap) : true; ViewExtension->SubscribeToPostProcessingPass(SceneViewPass, View, SceneViewExtensionDelegates[SceneViewPassId], bIsEnabled); } for (int32 SceneViewPassId = FirstAfterPass; SceneViewPassId < static_cast<int32>(ISceneViewExtension::EPostProcessingPass::MAX); SceneViewPassId++) { const ISceneViewExtension::EPostProcessingPass SceneViewPass = static_cast<ISceneViewExtension::EPostProcessingPass>(SceneViewPassId); const EPass PostProcessingPass = TranslatePass(SceneViewPass); ViewExtension->SubscribeToPostProcessingPass( SceneViewPass, View, PassSequence.GetAfterPassCallbacks(PostProcessingPass), PassSequence.IsEnabled(PostProcessingPass)); } }FSceneViewExtensions::NewExtension() ↓ 创建 FAutoRegister ↓ 构造 FLearningPostProcessViewExtension ↓ 调用 FSceneViewExtensionBase(AutoRegister) ↓ 把该实例的弱引用加入全局注册表 ↓ 返回 TSharedRef全局 ViewExtension 注册表 → 调用 IsActiveThisFrame() → 把激活的 Extension 放入 View.Family->ViewExtensions → 渲染阶段调用 SubscribeToPostProcessingPass()这里SubscribeToPostProcessingPass的SceneViewExtensionDelegates[SceneViewPassId]已经分类把对应类型的delegates给绑定好了，然后分不同passid在不同阶段执行！
这段代码的作用是：
遍历当前 View 的所有 SceneViewExtension，询问每个插件想订阅哪些 PostProcess 节点，并把插件 Delegate 保存到对应的回调数组中。
注意：这里只是“注册回调”，还没有真正执行插件 Pass。
简化成伪代码：
for (每个插件) { for (每个PostProcess插入点) { 询问插件： “你要不要在这个位置添加回调？” } }for (const TSharedRef<ISceneViewExtension>& ViewExtension
: View.Family->ViewExtensions)
遍历所有注册了ViewExtension的接口
分界点：
constexpr int32 FirstAfterPass = static_cast<int32>( ISceneViewExtension::EPostProcessingPass::MotionBlur);EPostProcessingPass顺序是：
BeforeDOF // 0 AfterDOF // 1 TranslucencyAfterDOF // 2 SSRInput // 3 ReplacingTonemapper // 4 MotionBlur // FirstAfterPass Tonemap FXAA SMAA VisualizeDepthOfField前五个位置由PostProcessing.cpp在特定位置手动执行。
从 MotionBlur 开始的节点，可以统一放进PassSequence。
EPostProcessingPass枚举中， MotionBlur编号之前的特殊插件挂载点并且循环当前做的只是询问插件是否订阅：
ViewExtension->SubscribeToPostProcessingPass(...)同一个 ViewExtension 可以把：
- 同一个回调函数绑定到多个阶段；
- 不同回调函数绑定到不同阶段。
那么一帧内大致是：
BeforeDOF → OutlineCallback 执行一次 景深处理 AfterDOF → OutlineCallback 再执行一次遍历每一个viewextension，然后一个一个问，这个阶段要不要绑定，要绑定我就subscribe
具体是否绑定是上面代码遍历前期的各个postprocess阶段，传到ViewExtension里面，看是否绑定，ViewExtension会实现对应的SubscribeToPostProcessingPass函数，里面会判断if(id 是否等于对应阶段）是对应阶段才进行注册绑定
例如：
void FLearningPostProcessViewExtension:: SubscribeToPostProcessingPass( EPostProcessingPass PassId, const FSceneView& View, FPostProcessingPassDelegateArray& InOutPassCallbacks, bool bIsPassEnabled) { if (PassId != EPostProcessingPass::Tonemap) { return; } if (!bIsPassEnabled) { return; } if (CVarLearningPostProcessEnable.GetValueOnRenderThread() == 0) { return; } // 当前 Shader 只编译 SM5 及以上平台。 if (!IsFeatureLevelSupported( View.GetShaderPlatform(), ERHIFeatureLevel::SM5)) { return; } InOutPassCallbacks.Add( FPostProcessingPassDelegate::CreateRaw( this, &FLearningPostProcessViewExtension:: PostProcessPassAfterTonemap_RenderThread)); }问：所以这里为什么就replacingtonemapper要判断isenable其他直接返回true呢?
答：因为前面几个并不是“替换某个功能”，而是固定的插入位置；只有ReplacingTonemapper依赖 Tonemap 本身存在。
对应第一类的执行在：
FScreenPassTexture AddSceneViewExtensionPassChain( FRDGBuilder& GraphBuilder, const FViewInfo& View, const FPostProcessMaterialInputs& InputsTemplate, const FPostProcessingPassDelegateArray& Delegates, EPostProcessMaterialInput MaterialInput = EPostProcessMaterialInput::SceneColor) { FScreenPassTextureSlice CurrentInput = InputsTemplate.GetInput(MaterialInput); FScreenPassTexture Outputs; for (int32 DelegateIndex = 0; DelegateIndex < Delegates.Num(); ++DelegateIndex) { FPostProcessMaterialInputs Inputs = InputsTemplate; Inputs.SetInput(MaterialInput, CurrentInput); Outputs = Delegates[DelegateIndex].Execute(GraphBuilder, View, Inputs); CurrentInput = FScreenPassTextureSlice::CreateFromScreenPassTexture(GraphBuilder, Outputs); } if (!Outputs.IsValid()) { Outputs = FScreenPassTexture::CopyFromSlice(GraphBuilder, CurrentInput); } return Outputs; }; }第二类的执行之一在：
const auto AddAfterPass = [&](EPass InPass, FScreenPassTexture InSceneColor) -> FScreenPassTexture { // In some cases (e.g. OCIO color conversion) we want View Extensions to be able to add extra custom post processing after the pass. FPostProcessingPassDelegateArray& PassCallbacks = PassSequence.GetAfterPassCallbacks(InPass); if (PassCallbacks.Num()) { FPostProcessMaterialInputs InOutPostProcessAfterPassInputs = GetPostProcessMaterialInputs(InSceneColor); for (int32 AfterPassCallbackIndex = 0; AfterPassCallbackIndex < PassCallbacks.Num(); AfterPassCallbackIndex++) { InOutPostProcessAfterPassInputs.SetInput(GraphBuilder, EPostProcessMaterialInput::SceneColor, InSceneColor); FAfterPassCallbackDelegate& AfterPassCallback = PassCallbacks[AfterPassCallbackIndex]; PassSequence.AcceptOverrideIfLastPass(InPass, InOutPostProcessAfterPassInputs.OverrideOutput, AfterPassCallbackIndex); InSceneColor = AfterPassCallback.Execute(GraphBuilder, View, InOutPostProcessAfterPassInputs); } } return MoveTemp(InSceneColor); };都是在不同地方然后取出不同的epass类型注册的delegates数组然后执行
第一类：
SceneViewExtensionDelegates[PassId]是PostProcessing.cpp中的局部数组，在 BeforeDOF、SSRInput 等特殊位置手动调用。不同位置还可能使用不同输入：
SceneColor SeparateTranslucency SSRInput CombinedBloom第二类：
PassSequence.GetAfterPassCallbacks(EPass)数组由PassSequence管理，统一通过AddAfterPass()执行。它额外参与：
- 最后一个有效 Pass 的判断。
OverrideOutput管理。- 直接写 ViewFamily 最终输出。
- 原生 Pass 启用状态。
- 多个回调串联后的最终输出选择。
onst EPass PostProcessingPass = TranslatePass(SceneViewPass);例如：
EPostProcessingPass::MotionBlur → EPass::MotionBlur EPostProcessingPass::Tonemap → EPass::Tonemap EPostProcessingPass::FXAA → EPass::FXAAPassSequence.GetAfterPassCallbacks(PostProcessingPass)意思是在这个Pass执行完之后执行
第一个 for： 回调放进独立数组，之后在 PostProcessing.cpp 的指定代码位置手动执行 第二个 for： 回调放进 PassSequence，某个 Pass 执行完成后自动接着执行实际代码：
.uplugin:
{ "FileVersion": 3, "Version": 1, "VersionName": "1.0", "FriendlyName": "Learning Post Process", "Description": "A minimal Scene View Extension post-processing pass example.", "Category": "Rendering", "CreatedBy": "Learning", "CanContainContent": false, "EnabledByDefault": true, "Modules": [ { "Name": "LearningPostProcess", "Type": "Runtime", "LoadingPhase": "PostConfigInit" } ] }.Build.cs:
// Some copyright should be here... using UnrealBuildTool; public class LearningPostProcess : ModuleRules { public LearningPostProcess(ReadOnlyTargetRules Target) : base(Target) { PCHUsage = ModuleRules.PCHUsageMode.UseExplicitOrSharedPCHs; PublicIncludePaths.AddRange( new string[] { // ... add public include paths required here ... } ); PrivateIncludePaths.AddRange( new string[] { // ... add other private include paths required here ... } ); PublicDependencyModuleNames.AddRange( new string[] { "Core", "CoreUObject", "Engine", "RenderCore" // ... add other public dependencies that you statically link with here ... } ); PrivateDependencyModuleNames.AddRange( new string[] { "Projects", "RHI", "Renderer" // ... add private dependencies that you statically link with here ... } ); DynamicallyLoadedModuleNames.AddRange( new string[] { // ... add any modules that your module loads dynamically here ... } ); } }.LearningPostProcess.cpp:
// Copyright Epic Games, Inc. All Rights Reserved. #include "LearningPostProcess.h" #include "LearningPostProcessViewExtension.h" #include "Engine/Engine.h" #include "Interfaces/IPluginManager.h" #include "Misc/CoreDelegates.h" #include "Misc/Paths.h" #include "SceneViewExtension.h" #include "ShaderCore.h" void FLearningPostProcessModule::StartupModule() { const TSharedPtr<IPlugin> Plugin = IPluginManager::Get().FindPlugin(TEXT("LearningPostProcess")); checkf( Plugin.IsValid(), TEXT("LearningPostProcess plugin was not found.")); const FString ShaderDirectory = FPaths::Combine( Plugin->GetBaseDir(), TEXT("Shaders")); AddShaderSourceDirectoryMapping( TEXT("/Plugin/LearningPostProcess"), ShaderDirectory); // PostConfigInit 时 GEngine 可能尚未完成初始化。 if (GEngine != nullptr) { RegisterViewExtension(); } else { PostEngineInitHandle = FCoreDelegates::OnPostEngineInit.AddRaw( this, &FLearningPostProcessModule::RegisterViewExtension); } } void FLearningPostProcessModule::ShutdownModule() { if (PostEngineInitHandle.IsValid()) { FCoreDelegates::OnPostEngineInit.Remove( PostEngineInitHandle); PostEngineInitHandle.Reset(); } // SceneViewExtension 系统保存的是弱引用。 // 释放这个强引用即可注销 Extension。 ViewExtension.Reset(); } void FLearningPostProcessModule::RegisterViewExtension() { if (!ViewExtension.IsValid()) { ViewExtension = FSceneViewExtensions::NewExtension< FLearningPostProcessViewExtension>(); } } IMPLEMENT_MODULE( FLearningPostProcessModule, LearningPostProcess)const TSharedPtr<IPlugin> Plugin = IPluginManager::Get().FindPlugin(TEXT("LearningPostProcess"));通过全局插件管理器，按名称查找
"LearningPostProcess"这个插件，得到它的接口指针。
const FString ShaderDirectory = FPaths::Combine(Plugin->GetBaseDir(), TEXT("Shaders"));Plugin->GetBaseDir()返回该插件在磁盘上的根目录（例如D:/Project/Plugins/LearningPostProcess/）。FPaths::Combine将其与Shaders子目录拼接，得到物理路径，比如D:/Project/Plugins/LearningPostProcess/Shaders。
AddShaderSourceDirectoryMapping( TEXT("/Plugin/LearningPostProcess"), ShaderDirectory);核心操作：建立一个虚拟路径到物理路径的映射。
第一个参数是虚拟路径
"/Plugin/LearningPostProcess"，在着色器代码中用它来引用文件。第二个参数是上面拼接出的实际文件夹路径。
调用后，引擎的着色器预处理器在处理
#include时，就会把"/Plugin/LearningPostProcess/xxx.usf"自动转换为ShaderDirectory/xxx.usf。
if (GEngine) { RegisterViewExtension(); }GEngine
全局引擎指针，指向UEngine实例。它是在引擎初始化过程中由UEngine::Init()创建的。在模块的StartupModule()阶段，它可能还是nullptr，具体取决于模块加载顺序（例如在编辑器启动、项目启动等场景）。
RegisterViewExtension()
就是之前在PostProcessing.cpp里面给出的拓展Extension，我们需要把插件的给注册进里面
else分支
如果GEngine还是空，则绑定到FCoreDelegates::OnPostEngineInit这个全局委托。该委托会在引擎完全初始化后触发（UEngine::Init()结束时广播）。AddRaw将一个原始 C++ 成员函数指针绑定到委托上。返回值
PostEngineInitHandle是一个句柄，通常用于后续在ShutdownModule()时通过FCoreDelegates::OnPostEngineInit.Remove(Handle)解绑，避免悬空指针。
virtual void ShutdownModule() override { if (PostEngineInitHandle.IsValid()) { FCoreDelegates::OnPostEngineInit.Remove(PostEngineInitHandle); PostEngineInitHandle.Reset(); } }作用：如果在模块启动时，
GEngine还未初始化，我们就绑定了一个委托到OnPostEngineInit。现在模块关闭了，必须把这个绑定解除，防止委托还在持有指向已释放模块成员的原始指针，导致未来触发时崩溃。Remove()从委托列表里移除该句柄对应的绑定。Reset()将句柄本身清空（标记为无效）。
void RegisterViewExtension() { if (!ViewExtension.IsValid()) { ViewExtension = FSceneViewExtensions::NewExtension< FLearningPostProcessViewExtension>(); } }这就是实际创建并注册自定义扩展的地方。
IMPLEMENT_MODULE(FLearningPostProcessModule, LearningPostProcess)FLearningPostProcessModule就是我们一直在讨论的那个类，其中包含了StartupModule()和ShutdownModule()。这个宏告诉引擎：“这是我的模块类，请用StartupModule\ShutdownModule来初始化/关闭这个模块。
LearningPostProcess.h:
// Copyright Epic Games, Inc. All Rights Reserved. #pragma once #include "CoreMinimal.h" #include "Modules/ModuleManager.h" class FLearningPostProcessViewExtension; class FLearningPostProcessModule final : public IModuleInterface { public: virtual void StartupModule() override; virtual void ShutdownModule() override; private: void RegisterViewExtension(); FDelegateHandle PostEngineInitHandle; TSharedPtr< FLearningPostProcessViewExtension, ESPMode::ThreadSafe> ViewExtension; };这里就没啥好讲的，就是声明变量
LearningPostProcessViewExtension.h:
// Copyright Epic Games, Inc. All Rights Reserved. #pragma once #include "SceneViewExtension.h" class FLearningPostProcessViewExtension final : public FSceneViewExtensionBase { public: explicit FLearningPostProcessViewExtension( const FAutoRegister& AutoRegister); virtual bool IsActiveThisFrame_Internal( const FSceneViewExtensionContext& Context) const override; virtual void SubscribeToPostProcessingPass( EPostProcessingPass PassId, const FSceneView& View, FPostProcessingPassDelegateArray& InOutPassCallbacks, bool bIsPassEnabled) override; private: FScreenPassTexture PostProcessPassAfterTonemap_RenderThread( FRDGBuilder& GraphBuilder, const FSceneView& View, const FPostProcessMaterialInputs& Inputs); };在.cpp详细描述具体函数含义
LearningPostProcessViewExtension.cpp
// Copyright Epic Games, Inc. All Rights Reserved. #include "LearningPostProcessViewExtension.h" #include "DataDrivenShaderPlatformInfo.h" #include "GlobalShader.h" #include "HAL/IConsoleManager.h" #include "PixelShaderUtils.h" #include "PostProcess/PostProcessMaterialInputs.h" #include "RenderGraphBuilder.h" #include "RHIStaticStates.h" #include "SceneView.h" #include "ScreenPass.h" #include "ShaderParameterStruct.h" static TAutoConsoleVariable<int32> CVarLearningPostProcessEnable( TEXT("r.LearningPostProcess.Enable"), 1, TEXT("Enable the LearningPostProcess pass.\n") TEXT("0: Disabled\n") TEXT("1: Enabled"), ECVF_RenderThreadSafe); static TAutoConsoleVariable<float> CVarLearningPostProcessIntensity( TEXT("r.LearningPostProcess.Intensity"), 0.5f, TEXT("Tint intensity in the range 0 to 1."), ECVF_RenderThreadSafe); static TAutoConsoleVariable<float> CVarLearningPostProcessTintR( TEXT("r.LearningPostProcess.TintR"), 1.0f, TEXT("Red component of the tint color."), ECVF_RenderThreadSafe); static TAutoConsoleVariable<float> CVarLearningPostProcessTintG( TEXT("r.LearningPostProcess.TintG"), 0.5f, TEXT("Green component of the tint color."), ECVF_RenderThreadSafe); static TAutoConsoleVariable<float> CVarLearningPostProcessTintB( TEXT("r.LearningPostProcess.TintB"), 0.5f, TEXT("Blue component of the tint color."), ECVF_RenderThreadSafe); class FLearningPostProcessPS final : public FGlobalShader { public: DECLARE_GLOBAL_SHADER(FLearningPostProcessPS); SHADER_USE_PARAMETER_STRUCT( FLearningPostProcessPS, FGlobalShader); BEGIN_SHADER_PARAMETER_STRUCT(FParameters, ) SHADER_PARAMETER_RDG_TEXTURE( Texture2D, InputTexture) SHADER_PARAMETER_SAMPLER( SamplerState, InputSampler) SHADER_PARAMETER( FScreenTransform, SvPositionToInputTextureUV) SHADER_PARAMETER( FLinearColor, TintColor) SHADER_PARAMETER( float, Intensity) RENDER_TARGET_BINDING_SLOTS() END_SHADER_PARAMETER_STRUCT() static bool ShouldCompilePermutation( const FGlobalShaderPermutationParameters& Parameters) { return IsFeatureLevelSupported( Parameters.Platform, ERHIFeatureLevel::SM5); } }; IMPLEMENT_GLOBAL_SHADER( FLearningPostProcessPS, "/Plugin/LearningPostProcess/Private/LearningPostProcess.usf", "LearningPostProcessPS", SF_Pixel); FLearningPostProcessViewExtension:: FLearningPostProcessViewExtension( const FAutoRegister& AutoRegister) : FSceneViewExtensionBase(AutoRegister) { } bool FLearningPostProcessViewExtension:: IsActiveThisFrame_Internal( const FSceneViewExtensionContext& Context) const { return CVarLearningPostProcessEnable.GetValueOnAnyThread() != 0; } void FLearningPostProcessViewExtension:: SubscribeToPostProcessingPass( EPostProcessingPass PassId, const FSceneView& View, FPostProcessingPassDelegateArray& InOutPassCallbacks, bool bIsPassEnabled) { if (PassId != EPostProcessingPass::Tonemap) { return; } if (!bIsPassEnabled) { return; } if (CVarLearningPostProcessEnable.GetValueOnRenderThread() == 0) { return; } // 当前 Shader 只编译 SM5 及以上平台。 if (!IsFeatureLevelSupported( View.GetShaderPlatform(), ERHIFeatureLevel::SM5)) { return; } InOutPassCallbacks.Add( FPostProcessingPassDelegate::CreateRaw( this, &FLearningPostProcessViewExtension:: PostProcessPassAfterTonemap_RenderThread)); } FScreenPassTexture FLearningPostProcessViewExtension:: PostProcessPassAfterTonemap_RenderThread( FRDGBuilder& GraphBuilder, const FSceneView& View, const FPostProcessMaterialInputs& Inputs) { const FScreenPassTexture SceneColor = FScreenPassTexture::CopyFromSlice( GraphBuilder, Inputs.GetInput( EPostProcessMaterialInput::SceneColor)); check(SceneColor.IsValid()); // 当这个回调是后处理链最后一个 pass 时， // 引擎会传入 OverrideOutput。 FScreenPassRenderTarget Output = Inputs.OverrideOutput; if (!Output.IsValid()) { Output = FScreenPassRenderTarget::CreateFromInput( GraphBuilder, SceneColor, View.GetOverwriteLoadAction(), TEXT("LearningPostProcess.Output")); } const FScreenPassTextureViewport InputViewport(SceneColor); const FScreenPassTextureViewport OutputViewport(Output); FLearningPostProcessPS::FParameters* PassParameters = GraphBuilder.AllocParameters< FLearningPostProcessPS::FParameters>(); PassParameters->InputTexture = SceneColor.Texture; PassParameters->InputSampler = TStaticSamplerState< SF_Bilinear, AM_Clamp, AM_Clamp, AM_Clamp>::GetRHI(); // SV_POSITION -> Output Viewport UV -> Input Texture UV。 PassParameters->SvPositionToInputTextureUV = FScreenTransform::ChangeTextureBasisFromTo( OutputViewport, FScreenTransform::ETextureBasis::TexelPosition, FScreenTransform::ETextureBasis::ViewportUV) * FScreenTransform::ChangeTextureBasisFromTo( InputViewport, FScreenTransform::ETextureBasis::ViewportUV, FScreenTransform::ETextureBasis::TextureUV); PassParameters->TintColor = FLinearColor( CVarLearningPostProcessTintR .GetValueOnRenderThread(), CVarLearningPostProcessTintG .GetValueOnRenderThread(), CVarLearningPostProcessTintB .GetValueOnRenderThread(), 1.0f); PassParameters->Intensity = FMath::Clamp( CVarLearningPostProcessIntensity .GetValueOnRenderThread(), 0.0f, 1.0f); PassParameters->RenderTargets[0] = Output.GetRenderTargetBinding(); const FGlobalShaderMap* ShaderMap = GetGlobalShaderMap( View.GetFeatureLevel()); const TShaderMapRef<FLearningPostProcessPS> PixelShader(ShaderMap); FPixelShaderUtils::AddFullscreenPass( GraphBuilder, ShaderMap, RDG_EVENT_NAME( "LearningPostProcess AfterTonemap"), PixelShader, PassParameters, Output.ViewRect); return MoveTemp(Output); }FLearningPostProcessViewExtension:: FLearningPostProcessViewExtension( const FAutoRegister& AutoRegister) : FSceneViewExtensionBase(AutoRegister) { }相当于之前在引擎的PS，这里面就要对Extension多做一下构造函数，函数里面不需要任何逻辑
bool FLearningPostProcessViewExtension:: IsActiveThisFrame_Internal( const FSceneViewExtensionContext& Context) const { return CVarLearningPostProcessEnable.GetValueOnAnyThread() != 0; }这是FLearningPostProcessViewExtension继承的FSceneViewExtensionBase里面的ISceneViewExtension的一个受保护的虚函数，如果返回false就不会调用资源来执行接下来的逻辑，true才会
void FLearningPostProcessViewExtension:: SubscribeToPostProcessingPass( EPostProcessingPass PassId, const FSceneView& View, FPostProcessingPassDelegateArray& InOutPassCallbacks, bool bIsPassEnabled) { if (PassId != EPostProcessingPass::Tonemap) { return; } if (!bIsPassEnabled) { return; } if (CVarLearningPostProcessEnable.GetValueOnRenderThread() == 0) { return; } // 当前 Shader 只编译 SM5 及以上平台。 if (!IsFeatureLevelSupported( View.GetShaderPlatform(), ERHIFeatureLevel::SM5)) { return; } InOutPassCallbacks.Add( FPostProcessingPassDelegate::CreateRaw( this, &FLearningPostProcessViewExtension:: PostProcessPassAfterTonemap_RenderThread)); }这里就是看是否是对应Pass阶段，Pass是否启用，命令行，命令行是否启用，是否支持对应平台，如果都OK，那么就绑定到对应的delegate上，方便之后对应的epass阶段在postprocessing.cpp里面进行execute执行对应的回调函数：FScreenPassTexture
FLearningPostProcessViewExtension::
PostProcessPassAfterTonemap_RenderThread。
剩下这个回调函数就是给PS赋值，然后
AddFullscreenPass到任务队列
LearningPostProcess.usf:
// Copyright Epic Games, Inc. All Rights Reserved. #include "/Engine/Private/Common.ush" #include "/Engine/Private/ScreenPass.ush" Texture2D InputTexture; SamplerState InputSampler; FScreenTransform SvPositionToInputTextureUV; float4 TintColor; float Intensity; void LearningPostProcessPS( float4 SvPosition : SV_POSITION, out float4 OutColor : SV_Target0) { const float2 UV = ApplyScreenTransform( SvPosition.xy, SvPositionToInputTextureUV); const float4 SceneColor = Texture2DSample( InputTexture, InputSampler, UV); const float3 TintedColor = SceneColor.rgb * TintColor.rgb; OutColor = float4( lerp(SceneColor.rgb, TintedColor, saturate(Intensity)), SceneColor.a); }这里的.usf就很简单，就是原场景颜色 * 一个我们自定义的颜色即可
总体来说，就是相对于直接改引擎，我们先要在module注册一个ViewExtension，第二个就是ViewExtension回调函数的参数FViewInfo变成了FSceneView，其他基本保持一致