虚幻4渲染编程（Shader篇）【第二卷：不用虚幻4Shader管线使用自己的shader】

123456911 · 发表于 2020-12-28 10:45

MY BLOG DIRECTORY：
INTRODUCTION：
下面的球使用的是我用GlobalShader画出来的RT赋上的颜色
这个球的颜色是通过自己的shader实现的：
下面就来一步一步实现使用自己的shader吧。
MAIN CONTENT：
首先我们先创建一个插件。插件其实相当于一个独立的模块，我不想再项目里做，当然再游戏模块里做也是没问题的。我们先把整个流程搞清楚了再去改引擎。
首先创建个插件，名字取为ShadertestPlugin
然后打开工程里的这个插件，在插件目录下加一个Shaders文件夹

然后再在Shaders文件夹里加Private文件夹

然后再在private里面夹里新建一个文本文档，然后把后缀名改位.usf

在这个MyShader.usf里键入如下代码：
#include &#34;/Engine/Public/Platform.ush&#34;

float4 SimpleColor;
void MainVS(
in float4 InPosition : ATTRIBUTE0,
out float4 OutPosition : SV_POSITION
)
{
// screenspace position from vb
OutPosition = InPosition;
}

void MainPS(
out float4 OutColor : SV_Target0
)
{
OutColor = SimpleColor;
}我声明了一个MyColor的颜色，这个变量后面会和c++绑定，到时候就可以让它跟cpu交互了。然后声明了一个顶点着色器和像素着色i器。
完成了这个之后，再在插件的source文件夹下加两个文件

新建两个文本文档然后把后缀改位.h和.cpp就可以了。做完这些之后记得右键Uproject文件重写generate一下工程

然后重新加载vs项目就可以啦。
然后在把ShadertestPlugin.uplugin文件改一下，如下图。把加载顺序改成在引擎前加载。PostConfigInit。shader必须要在引擎加载完成前加载完才行。
做完这个后，再在MyShader.h中打入如下代码：
然后再在MyShader.cpp中打入如下代码：
// Copyright 1998-2018 Epic Games, Inc. All Rights Reserved.

#include &#34;MyShaderTest.h&#34;

#include &#34;Classes/Engine/TextureRenderTarget2D.h&#34;
#include &#34;Classes/Engine/World.h&#34;
#include &#34;Public/GlobalShader.h&#34;
#include &#34;Public/PipelineStateCache.h&#34;
#include &#34;Public/RHIStaticStates.h&#34;
#include &#34;Public/SceneUtils.h&#34;
#include &#34;Public/SceneInterface.h&#34;
#include &#34;Public/ShaderParameterUtils.h&#34;
#include &#34;Public/Logging/MessageLog.h&#34;
#include &#34;Public/Internationalization/Internationalization.h&#34;
#include &#34;Public/StaticBoundShaderState.h&#34;

#define LOCTEXT_NAMESPACE &#34;TestShader&#34;

UTestShaderBlueprintLibrary::UTestShaderBlueprintLibrary(const FObjectInitializer& ObjectInitializer)
: Super(ObjectInitializer)
{

}

class FMyShaderTest : public FGlobalShader
{
public:

FMyShaderTest(){}

FMyShaderTest(const ShaderMetaType::CompiledShaderInitializerType& Initializer)
      : FGlobalShader(Initializer)
{
      SimpleColorVal.Bind(Initializer.ParameterMap, TEXT(&#34;SimpleColor&#34;));
}

static bool ShouldCache(EShaderPlatform Platform)
{
      return true;
}

static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters)
{
      //return IsFeatureLevelSupported(Parameters.Platform, ERHIFeatureLevel::SM4);
      return true;
}

static void ModifyCompilationEnvironment(const FGlobalShaderPermutationParameters& Parameters, FShaderCompilerEnvironment& OutEnvironment)
{
      FGlobalShader::ModifyCompilationEnvironment(Parameters, OutEnvironment);
      OutEnvironment.SetDefine(TEXT(&#34;TEST_MICRO&#34;), 1);
}

void SetParameters(
      FRHICommandListImmediate& RHICmdList,
      const FLinearColor &MyColor
      )
{
      SetShaderValue(RHICmdList, GetPixelShader(), SimpleColorVal, MyColor);
}

virtual bool Serialize(FArchive& Ar) override
{
      bool bShaderHasOutdatedParameters = FGlobalShader::Serialize(Ar);
      Ar << SimpleColorVal;
      return bShaderHasOutdatedParameters;
}

private:

FShaderParameter SimpleColorVal;

};

class FShaderTestVS : public FMyShaderTest
{
DECLARE_SHADER_TYPE(FShaderTestVS, Global);

public:
FShaderTestVS(){}

FShaderTestVS(const ShaderMetaType::CompiledShaderInitializerType& Initializer)
      : FMyShaderTest(Initializer)
{

}
};

class FShaderTestPS : public FMyShaderTest
{
DECLARE_SHADER_TYPE(FShaderTestPS, Global);

public:
FShaderTestPS() {}

FShaderTestPS(const ShaderMetaType::CompiledShaderInitializerType& Initializer)
      : FMyShaderTest(Initializer)
{

}
};

IMPLEMENT_SHADER_TYPE(, FShaderTestVS, TEXT(&#34;/Plugin/ShadertestPlugin/Private/MyShader.usf&#34;), TEXT(&#34;MainVS&#34;), SF_Vertex)
IMPLEMENT_SHADER_TYPE(, FShaderTestPS, TEXT(&#34;/Plugin/ShadertestPlugin/Private/MyShader.usf&#34;), TEXT(&#34;MainPS&#34;), SF_Pixel)

static void DrawTestShaderRenderTarget_RenderThread(
FRHICommandListImmediate& RHICmdList,
FTextureRenderTargetResource* OutputRenderTargetResource,
ERHIFeatureLevel::Type FeatureLevel,
FName TextureRenderTargetName,
FLinearColor MyColor
)
{
check(IsInRenderingThread());

#if WANTS_DRAW_MESH_EVENTS
FString EventName;
TextureRenderTargetName.ToString(EventName);
SCOPED_DRAW_EVENTF(RHICmdList, SceneCapture, TEXT(&#34;ShaderTest %s&#34;), *EventName);
#else
SCOPED_DRAW_EVENT(RHICmdList, DrawUVDisplacementToRenderTarget_RenderThread);
#endif

//设置渲染目标
SetRenderTarget(
      RHICmdList,
      OutputRenderTargetResource->GetRenderTargetTexture(),
      FTextureRHIRef(),
      ESimpleRenderTargetMode::EUninitializedColorAndDepth,
      FExclusiveDepthStencil::DepthNop_StencilNop
);

//设置视口
//FIntPoint DrawTargetResolution(OutputRenderTargetResource->GetSizeX(), OutputRenderTargetResource->GetSizeY());
//RHICmdList.SetViewport(0, 0, 0.0f, DrawTargetResolution.X, DrawTargetResolution.Y, 1.0f);

TShaderMap<FGlobalShaderType>* GlobalShaderMap = GetGlobalShaderMap(FeatureLevel);
TShaderMapRef<FShaderTestVS> VertexShader(GlobalShaderMap);
TShaderMapRef<FShaderTestPS> PixelShader(GlobalShaderMap);

// Set the graphic pipeline state.
FGraphicsPipelineStateInitializer GraphicsPSOInit;
RHICmdList.ApplyCachedRenderTargets(GraphicsPSOInit);
GraphicsPSOInit.DepthStencilState = TStaticDepthStencilState<false, CF_Always>::GetRHI();
GraphicsPSOInit.BlendState = TStaticBlendState<>::GetRHI();
GraphicsPSOInit.RasterizerState = TStaticRasterizerState<>::GetRHI();
GraphicsPSOInit.PrimitiveType = PT_TriangleList;
GraphicsPSOInit.BoundShaderState.VertexDeclarationRHI = GetVertexDeclarationFVector4();
GraphicsPSOInit.BoundShaderState.VertexShaderRHI = GETSAFERHISHADER_VERTEX(*VertexShader);
GraphicsPSOInit.BoundShaderState.PixelShaderRHI = GETSAFERHISHADER_PIXEL(*PixelShader);
SetGraphicsPipelineState(RHICmdList, GraphicsPSOInit);

//RHICmdList.SetViewport(0, 0, 0.0f, DrawTargetResolution.X, DrawTargetResolution.Y, 1.0f);
PixelShader->SetParameters(RHICmdList, MyColor);

// Draw grid.
//uint32 PrimitiveCount = 2;
//RHICmdList.DrawPrimitive(PT_TriangleList, 0, PrimitiveCount, 1);
FVector4 Vertices[4];
Vertices[0].Set(-1.0f, 1.0f, 0, 1.0f);
Vertices[1].Set(1.0f, 1.0f, 0, 1.0f);
Vertices[2].Set(-1.0f, -1.0f, 0, 1.0f);
Vertices[3].Set(1.0f, -1.0f, 0, 1.0f);
static const uint16 Indices[6] =
{
      0, 1, 2,
      2, 1, 3
};
//DrawPrimitiveUP(RHICmdList, PT_TriangleStrip, 2, Vertices, sizeof(Vertices[0]));
DrawIndexedPrimitiveUP(
      RHICmdList,
      PT_TriangleList,
      0,
      ARRAY_COUNT(Vertices),
      2,
      Indices,
      sizeof(Indices[0]),
      Vertices,
      sizeof(Vertices[0])
);

// Resolve render target.
RHICmdList.CopyToResolveTarget(
      OutputRenderTargetResource->GetRenderTargetTexture(),
      OutputRenderTargetResource->TextureRHI,
      false, FResolveParams());
}

void UTestShaderBlueprintLibrary::DrawTestShaderRenderTarget(
UTextureRenderTarget2D* OutputRenderTarget,
AActor* Ac,
FLinearColor MyColor
)
{
check(IsInGameThread());

if (!OutputRenderTarget)
{
      return;
}

FTextureRenderTargetResource* TextureRenderTargetResource = OutputRenderTarget->GameThread_GetRenderTargetResource();
UWorld* World = Ac->GetWorld();
ERHIFeatureLevel::Type FeatureLevel = World->Scene->GetFeatureLevel();
FName TextureRenderTargetName = OutputRenderTarget->GetFName();
ENQUEUE_RENDER_COMMAND(CaptureCommand)(
      [TextureRenderTargetResource, FeatureLevel, MyColor, TextureRenderTargetName](FRHICommandListImmediate& RHICmdList)
      {
         DrawTestShaderRenderTarget_RenderThread(RHICmdList,TextureRenderTargetResource, FeatureLevel, TextureRenderTargetName, MyColor);
      }
);

}

#undef LOCTEXT_NAMESPACE
稍后我会一行行解释这些代码的意思。然后我们要修改下c#文件
完成这些后再generate一下工程，然后就可以打开项目了。我们新建如下资源：

打开BP_Shader_Test蓝图做如下设置
新建一个颜色变量，然后再beginplay函数先清空一下我们的那张ShaderTestRT渲染目标，然后把我们这个shadertestrt渲染目标给我们的DrawTestShaderRenderTarget函数。还需要注意设置input，这样actor才能接收到我们的input事件。
做完这些之后再建一个材质，把RT拖到材质里（这里只是想让我们的shader效果被看到，我们的shader已经可以运作了）
这个操作其实已经是多pass了！！！然后把BP_Shader_Test拖到场景里，你按下1 2 3 就能看到如下效果了：
SUMMARY AND OUTLOOK：
虽然是一个简单的例子，但是终于可以在Unreal中使用自己的着色器了。
Enjoy it
NEXT：

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虚幻4渲染编程（Shader篇）【第二卷：不用虚幻4Shader管线使用自己的shader】

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