在shader文件中添加第二个颜色变量

UE4 ue4 render shader
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  1. 在shader文件中添加第二个颜色变量
    1. MyShader.usf
    2. MyShaderTest.h
    3. MyShaderTest.cpp
      1. DrawTestShaderRenderTarget
      2. FMyShaderTest
      3. VS 和 PS
      4. DrawTestShaderRenderTarget_RenderThread

在shader文件中添加第二个颜色变量

https://zhuanlan.zhihu.com/p/36635394
https://zhuanlan.zhihu.com/p/36695496
在看了shader编程的第二第三章后,觉的似懂非懂。再上面添加点东西,便于很深入的理解

MyShader.usf

  • 我们从目标要求开始,这里我想要使得输出颜色变为两个颜色的和，比如可以让颜色变成R+G,R+B等等
  • 这里我们现在usf文件中做如下添加和修改
// MyShader.usf
#include "/Engine/Public/Platform.ush"

float4 SimpleColor;
// 增加一个颜色采样的变量
float4 SimpleColor2;
void MainVS(
 in float4 InPosition : ATTRIBUTE0,
 out float4 OutPosition : SV_POSITION
 )
{
 // screenspace position from vb
    OutPosition = InPosition;
}

void MainPS(
    out float4 OutColor : SV_Target0
    )
{
    // 输出颜色变为两种颜色的叠加
    OutColor = (SimpleColor + SimpleColor2);
}

MyShaderTest.h

  • 因为添加了一个颜色变量，我们得将相关数据传进去。首先想到的是在蓝图中增加一个引脚
// MyShaderTest.h
#pragma once

#include "CoreMinimal.h"
#include "UObject/ObjectMacros.h"
#include "Classes/Kismet/BlueprintFunctionLibrary.h"
#include "MyShaderTest.generated.h"

UCLASS(MinimalAPI, meta = (ScriptName = "TestShaderLibrary"))
class UTestShaderBlueprintLibrary : public UBlueprintFunctionLibrary
{
    GENERATED_UCLASS_BODY()

        UFUNCTION(BlueprintCallable, Category = "ShaderTestPlugin", meta = (WorldContext = "WorldContextObject"))
        // 在这里增加一个FLinearColor的形参就是增加一个引脚
        static void DrawTestShaderRenderTarget(class UTextureRenderTarget2D* OutputRenderTarget, AActor* AC, FLinearColor MyColor,FLinearColor MyColor2);
};

MyShaderTest.cpp

DrawTestShaderRenderTarget

  • 为此我们需要进入cpp文件中,添加相应的形参。这个函数是在逻辑线程中调用。
  • ENQUEUE_RENDER_COMMAND向渲染线程压入一个渲染命令， 调用DrawTestShaderRenderTarget_RenderThread
  • 我们需要在lambda表达式中增加我们需要传的变量给渲染线程。

    DrawTestShaderRenderTarget中主要是对数据的获取和传递,一般不需要修改东西，只需要增加你要传递的各类数据。

// MyShaderTest.cpp
void UTestShaderBlueprintLibrary::DrawTestShaderRenderTarget(
    UTextureRenderTarget2D* OutputRenderTarget,
    AActor* Ac,
    FLinearColor MyColor,
    FLinearColor MyColor2
)
{
    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,MyColor2, TextureRenderTargetName](FRHICommandListImmediate& RHICmdList)
    {
        DrawTestShaderRenderTarget_RenderThread(RHICmdList, TextureRenderTargetResource, FeatureLevel, TextureRenderTargetName, MyColor,MyColor2);
    }
    );

}

FMyShaderTest

  • 因为给DrawTestShaderRenderTarget_RenderThread添加了一个数据，所以需要修改其函数，但是这个比较复杂我们先看简单的。
  • 渲染管线中VS和PS是一定要自己配置的,所以创建自定义的VS和PS,需要从FGlobalShader继承。然后需要使用
IMPLEMENT_SHADER_TYPE(, FShaderTestVS, TEXT("/Plugin/ShadertestPlugin/Private/MyShader.usf"), TEXT("MainVS"), SF_Vertex)
IMPLEMENT_SHADER_TYPE(, FShaderTestPS, TEXT("/Plugin/ShadertestPlugin/Private/MyShader.usf"), TEXT("MainPS"), SF_Pixel)

这个语句来使相关类和Vertex Shader或Pixel Shader文件绑定，这样渲染管线中将会使用我们自定义的定点着色器和像素着色器

  • 因为在VS和PS中有些配置是一样的,所以我们可以先从FGlobalShader派生一个FMyShaderTest的类,然后再从FMyShaderTest派生出我们的FShaderTestVS和FShaderTestPS。
// MyShaderTest.cpp
class FMyShaderTest : public FGlobalShader
{
public:

    FMyShaderTest() {}

    FMyShaderTest(const ShaderMetaType::CompiledShaderInitializerType& Initializer)
        : FGlobalShader(Initializer)
    {
        SimpleColorVal.Bind(Initializer.ParameterMap, TEXT("SimpleColor"));
        SimpleColorVal2.Bind(Initializer.ParameterMap, TEXT("SimpleColor2"));
    }

    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("TEST_MICRO"), 1);
    }

    void SetParameters(
        FRHICommandListImmediate& RHICmdList,
        const FLinearColor &MyColor,
        const FLinearColor &MyColor2
    )
    {
        SetShaderValue(RHICmdList, GetPixelShader(), SimpleColorVal, MyColor);
        SetShaderValue(RHICmdList, GetPixelShader(), SimpleColorVal2, MyColor2);
    }

    virtual bool Serialize(FArchive& Ar) override
    {
        bool bShaderHasOutdatedParameters = FGlobalShader::Serialize(Ar);
        Ar << SimpleColorVal;
        Ar << SimpleColorVal2;
        return bShaderHasOutdatedParameters;
    }

private:

    FShaderParameter SimpleColorVal;
    FShaderParameter SimpleColorVal2;

};

其中

// MyShaderTest.cpp
SimpleColorVal.Bind(Initializer.ParameterMap, TEXT("SimpleColor"));
SimpleColorVal2.Bind(Initializer.ParameterMap, TEXT("SimpleColor2"));
// MyShader.usf
float4 SimpleColor;
float4 SimpleColor2;
  • 这是将FMyShaderTest中的私有变量与MyShader.usf中变量进行绑定。

  • 但是我们注意到我们还没有将颜色输入到FMyShaderTest中的私有变量。因此我们需要写一个函数用于把我们的颜色信息传到shader里。。

    // MyShaderTest.cpp
void SetParameters(
  FRHICommandListImmediate& RHICmdList,
  const FLinearColor &MyColor,
  const FLinearColor &MyColor2
)
{
  SetShaderValue(RHICmdList, GetPixelShader(), SimpleColorVal, MyColor);
  SetShaderValue(RHICmdList, GetPixelShader(), SimpleColorVal2, MyColor2);
}

  • 因为这些参数在PS中使用到，所以此处使用GetPixelShader()参数

    virtual bool Serialize(FArchive& Ar) override
    {
        bool bShaderHasOutdatedParameters = FGlobalShader::Serialize(Ar);
        Ar << SimpleColorVal;
        Ar << SimpleColorVal2;
        return bShaderHasOutdatedParameters;
    }
  • 虚幻序列化，用于读取磁盘上的渲染数据，这里需要将我们所需要的SimpleColorVal，SimpleColorVal2;
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("TEST_MICRO"), 1);
}
  • 剩下这些可以暂时不用管。

    VS 和 PS

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("/Plugin/ShadertestPlugin/Private/MyShader.usf"), TEXT("MainVS"), SF_Vertex)
IMPLEMENT_SHADER_TYPE(, FShaderTestPS, TEXT("/Plugin/ShadertestPlugin/Private/MyShader.usf"), TEXT("MainPS"), SF_Pixel)
  • 这里从FMyShaderTest派生两个类分别利用IMPLEMENT_SHADER_TYPE宏指定为VS和PS
DECLARE_SHADER_TYPE(FShaderTestVS, Global);
  • 该宏用于把该Shader加入全局shadermap中，在运行前会将shadermap中的所以shader进行编译。

DrawTestShaderRenderTarget_RenderThread

static void DrawTestShaderRenderTarget_RenderThread(
    FRHICommandListImmediate& RHICmdList,
    FTextureRenderTargetResource* OutputRenderTargetResource,
    ERHIFeatureLevel::Type FeatureLevel,
    FName TextureRenderTargetName,
    FLinearColor MyColor,
    FLinearColor MyColor2
)
{
    check(IsInRenderingThread());

#if WANTS_DRAW_MESH_EVENTS  
    FString EventName;
    TextureRenderTargetName.ToString(EventName);
    SCOPED_DRAW_EVENTF(RHICmdList, SceneCapture, TEXT("ShaderTest %s"), *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,MyColor2);

    // 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());
}
  • 这是渲染线程中执行的函数
  • 这里只要在形参中添加MyColor2，以及SetParameters中添加MyColor2

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