UE4 にグローバル シェーダーを追加してみよう

// MyTest.usf 

// Simple pass-through vertex shader

void MainVS(
	in float4 InPosition :ATTRIBUTE0,
	out float4 Output :SV_POSITION
)
{
	Output = InPosition;
}

// Simple solid color pixel shader
float4 MyColor;
float4 MainPS() :SV_Target0
{
	return MyColor;
}

// This can go on a header or cpp file
class FMyTestVS : public FGlobalShader
{
	DECLARE_EXPORTED_SHADER_TYPE(FMyTestVS, Global, /*MYMODULE_API*/);
 
	FMyTestVS() { }
	FMyTestVS(const ShaderMetaType::CompiledShaderInitializerType& Initializer)
		:FGlobalShader(Initializer)
	{
	}
 
	static bool ShouldCache(EShaderPlatform Platform)
	{
		return true;
	}
};

// This needs to go on a cpp file
IMPLEMENT_SHADER_TYPE(, FMyTestVS, TEXT("MyTest"), TEXT("MainVS"), SF_Vertex);

class FMyTestPS : public FGlobalShader
{
	DECLARE_EXPORTED_SHADER_TYPE(FMyTestPS, Global, /*MYMODULE_API*/);
 
	FShaderParameter MyColorParameter;
 
	FMyTestPS() { }
	FMyTestPS(const ShaderMetaType::CompiledShaderInitializerType& Initializer)
		:FGlobalShader(Initializer)
	{
		MyColorParameter.Bind(Initializer.ParameterMap, TEXT("MyColor"), SPF_Mandatory);
	}
 
	static void ModifyCompilationEnvironment(EShaderPlatform Platform, FShaderCompilerEnvironment& OutEnvironment)
	{
		FGlobalShader::ModifyCompilationEnvironment(Platform, OutEnvironment);
		// Add your own defines for the shader code
		OutEnvironment.SetDefine(TEXT("MY_DEFINE"), 1);
	}
 
	static bool ShouldCache(EShaderPlatform Platform)
	{
		// Could skip compiling for Platform == SP_METAL for example
		return true;
	}
 
	// FShader interface.
	virtual bool Serialize(FArchive& Ar) override
	{
		bool bShaderHasOutdatedParameters = FGlobalShader::Serialize(Ar);
		Ar << MyColorParameter;
		return bShaderHasOutdatedParameters;
	}
 
	void SetColor(FRHICommandList& RHICmdList, const FLinearColor& Color)
	{
		SetShaderValue(RHICmdList, GetPixelShader(), MyColorParameter, Color);
	}
};

// Same source file as before, different entry point
IMPLEMENT_SHADER_TYPE(, FMyTestPS, TEXT("MyTest"), TEXT("MainPS"), SF_Pixel);

void RenderMyTest(FRHICommandList& RHICmdList, ERHIFeatureLevel::Type FeatureLevel, const FLinearColor& Color)
{
	// Get the collection of Global Shaders
	auto ShaderMap = GetGlobalShaderMap(FeatureLevel);

	// Get the actual shader instances off the ShaderMap
	TShaderMapRef MyVS(ShaderMap);
	TShaderMapRef MyPS(ShaderMap);

	// Declare a bound shader state using those shaders and apply it to the command list
	static FGlobalBoundShaderState MyTestBoundShaderState;
	SetGlobalBoundShaderState(RHICmdList, FeatureLevel, MyTestBoundShaderState, GetVertexDeclarationFVector4(), *MyVS, *MyPS);

	// Call our function to set up parameters
	MyPS->SetColor(RHICmdList, Color);
 
	// Setup the GPU in prep for drawing a solid quad
	RHICmdList.SetRasterizerState(TStaticRasterizerState<fm_solid, cm_none="">::GetRHI());
	RHICmdList.SetBlendState(TStaticBlendState<>::GetRHI());
	RHICmdList.SetDepthStencilState(TStaticDepthStencilState<false, cf_always="">::GetRHI(), 0);
 
	// Setup the vertices
	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);

	// Draw the quad
	DrawPrimitiveUP(RHICmdList, PT_TriangleStrip, 2, Vertices, sizeof(Vertices[0]));
}
</false,></fm_solid,>

static TAutoConsoleVariable CVarMyTest(
	TEXT("r.MyTest"),
	0,
	TEXT("Test My Global Shader, set it to 0 to disable, or to 1, 2 or 3 for fun!"),
	ECVF_RenderThreadSafe
);
 
void FDeferredShadingSceneRenderer::RenderFinish(FRHICommandListImmediate& RHICmdList)
{
	[...]
	// ***
	// Inserted code, just before finishing rendering, so we can overwrite the screen’s contents!
	int32 MyTestValue = CVarMyTest.GetValueOnAnyThread();
	if (MyTestValue != 0)
	{
		FLinearColor Color(MyTestValue == 1, MyTestValue == 2, MyTestValue == 3, 1);
		RenderMyTest(RHICmdList, FeatureLevel, Color);
	}
	// End Inserted code
	// ***
	FSceneRenderer::RenderFinish(RHICmdList);
	[...]
}