自学教程：C++ IsFeatureLevelSupported函数代码示例

	static bool ShouldCache(EShaderPlatform Platform)	{		if(!IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM5))		{			if(MSAASampleCount > 1)			{				return false;			}		}		return IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4);	}

	static bool ShouldCache(EShaderPlatform Platform,const FMaterial* Material,const FVertexFactoryType* VertexFactoryType)	{		// Only the local vertex factory supports the position-only stream		if (bUsePositionOnlyStream)		{			return VertexFactoryType->SupportsPositionOnly() && Material->IsSpecialEngineMaterial() 				&& IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM3);		}		// Only compile for the default material and masked materials		return (Material->IsSpecialEngineMaterial() || Material->IsMasked() || Material->MaterialModifiesMeshPosition())			 && IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM3);	}

	static bool ShouldCache(EShaderPlatform Platform)	{		if( IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM5) )		{			return true;		}		else if( IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4) )		{			return NumSamples <= 16;		}		else		{			return NumSamples <= 7;		}	}

	static bool ShouldCache(EShaderPlatform Platform,const FMaterial* Material,const FVertexFactoryType* VertexFactoryType)	{		return IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM5) 			&& DoesPlatformSupportDistanceFieldGI(Platform)			&& (FCString::Strstr(VertexFactoryType->GetName(), TEXT("LocalVertexFactory")) != NULL				|| FCString::Strstr(VertexFactoryType->GetName(), TEXT("InstancedStaticMeshVertexFactory")) != NULL);	}

	/**	  * Makes sure only shaders for materials that are explicitly flagged	  * as 'UsedAsDeferredDecal' in the Material Editor gets compiled into	  * the shader cache.	  */	static bool ShouldCache(EShaderPlatform Platform, const FMaterial* Material)	{		if (!Material->IsUsedWithDeferredDecal())		{			return false;		}		return IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4);	}

	static bool ShouldCache(EShaderPlatform Platform,const FMaterial* Material,const FVertexFactoryType* VertexFactoryType)	{		//Only compile the velocity shaders for the default material or if it's masked,		return ((Material->IsSpecialEngineMaterial() || Material->IsMasked() 			//or if the material is opaque and two-sided,			|| (Material->IsTwoSided() && !IsTranslucentBlendMode(Material->GetBlendMode()))			// or if the material modifies meshes			|| Material->MaterialMayModifyMeshPosition()))			&& IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4) && !FVelocityRendering::OutputsToGBuffer();	}

    static bool ShouldCache(EShaderPlatform Platform)    {        // Always allow simple bilinear upscale. (Provides upscaling for ES2 emulation)        if (Method == 1)        {            return true;        }        return IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4);    }

	static void ModifyCompilationEnvironment(EShaderPlatform Platform, FShaderCompilerEnvironment& OutEnvironment)	{		FGlobalShader::ModifyCompilationEnvironment(Platform, OutEnvironment);		if( !IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM5) )		{			//Need to hack in exposure scale for < SM5			OutEnvironment.SetDefine(TEXT("NO_EYEADAPTATION_EXPOSURE_FIX"), 1);		}	}

/** Updates the downsized depth buffer with the current full resolution depth buffer. */void FDeferredShadingSceneRenderer::UpdateDownsampledDepthSurface(){	if (GSceneRenderTargets.UseDownsizedOcclusionQueries() && IsFeatureLevelSupported(GRHIShaderPlatform, ERHIFeatureLevel::SM3))	{		RHISetRenderTarget(NULL, GSceneRenderTargets.GetSmallDepthSurface());		SCOPED_DRAW_EVENT(DownsampleDepth, DEC_SCENE_ITEMS);		for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)		{			const FViewInfo& View = Views[ViewIndex];			// Set shaders and texture			TShaderMapRef<FScreenVS> ScreenVertexShader(GetGlobalShaderMap());			TShaderMapRef<FDownsampleSceneDepthPS> PixelShader(GetGlobalShaderMap());			extern TGlobalResource<FFilterVertexDeclaration> GFilterVertexDeclaration;			SetGlobalBoundShaderState(DownsampleDepthBoundShaderState, GFilterVertexDeclaration.VertexDeclarationRHI, *ScreenVertexShader, *PixelShader);			RHISetBlendState(TStaticBlendState<CW_NONE>::GetRHI());			RHISetRasterizerState(TStaticRasterizerState<FM_Solid,CM_None>::GetRHI());			RHISetDepthStencilState(TStaticDepthStencilState<true,CF_Always>::GetRHI());			PixelShader->SetParameters(View);			const uint32 DownsampledX = FMath::Trunc(View.ViewRect.Min.X / GSceneRenderTargets.GetSmallColorDepthDownsampleFactor());			const uint32 DownsampledY = FMath::Trunc(View.ViewRect.Min.Y / GSceneRenderTargets.GetSmallColorDepthDownsampleFactor());			const uint32 DownsampledSizeX = FMath::Trunc(View.ViewRect.Width() / GSceneRenderTargets.GetSmallColorDepthDownsampleFactor());			const uint32 DownsampledSizeY = FMath::Trunc(View.ViewRect.Height() / GSceneRenderTargets.GetSmallColorDepthDownsampleFactor());			RHISetViewport(DownsampledX, DownsampledY, 0.0f, DownsampledX + DownsampledSizeX, DownsampledY + DownsampledSizeY, 1.0f);			DrawRectangle(				0, 0,				DownsampledSizeX, DownsampledSizeY,				View.ViewRect.Min.X, View.ViewRect.Min.Y,				View.ViewRect.Width(), View.ViewRect.Height(),				FIntPoint(DownsampledSizeX, DownsampledSizeY),				GSceneRenderTargets.GetBufferSizeXY(),				EDRF_UseTriangleOptimization);		}	}}

	static bool ShouldCache(EShaderPlatform Platform)	{		return IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4);	}

 //@todo-rco: Remove this when reenabling for OpenGL static bool ShouldCache( EShaderPlatform Platform )		{     return IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM5) && !IsOpenGLPlatform(Platform); }

bool FGPUSkinPassthroughVertexFactory::ShouldCache(EShaderPlatform Platform, const class FMaterial* Material, const class FShaderType* ShaderType){	// Passhrough is only valid on platforms with Compute Shader support	return GEnableGPUSkinCache && IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM5) && Super::ShouldCache(Platform, Material, ShaderType);}

	static bool ShouldCache(EShaderPlatform Platform)	{		return bEnablePlanarReflectionPrefilter ? IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4) : true;	}

/** * Renders the view family. */void FDeferredShadingSceneRenderer::Render(){	if(!ViewFamily.EngineShowFlags.Rendering)	{		return;	}	SCOPED_DRAW_EVENT(Scene,DEC_SCENE_ITEMS);	// Initialize global system textures (pass-through if already initialized).	GSystemTextures.InitializeTextures();	// Allocate the maximum scene render target space for the current view family.	GSceneRenderTargets.Allocate(ViewFamily);	// Find the visible primitives.	InitViews();	const bool bIsWireframe = ViewFamily.EngineShowFlags.Wireframe;	static const auto ClearMethodCVar = IConsoleManager::Get().FindTConsoleVariableDataInt(TEXT("r.ClearSceneMethod"));	bool bRequiresRHIClear = true;	bool bRequiresFarZQuadClear = false;	if (ClearMethodCVar)	{		switch (ClearMethodCVar->GetValueOnRenderThread())		{		case 0: // No clear			{				bRequiresRHIClear = false;				bRequiresFarZQuadClear = false;				break;			}				case 1: // RHIClear			{				bRequiresRHIClear = true;				bRequiresFarZQuadClear = false;				break;			}		case 2: // Clear using far-z quad			{				bRequiresFarZQuadClear = true;				bRequiresRHIClear = false;				break;			}		}	}	// Always perform a full buffer clear for wireframe, shader complexity view mode, and stationary light overlap viewmode.	if (bIsWireframe || ViewFamily.EngineShowFlags.ShaderComplexity || ViewFamily.EngineShowFlags.StationaryLightOverlap)	{		bRequiresRHIClear = true;	}	// force using occ queries for wireframe if rendering is parented or frozen in the first view	check(Views.Num());	#if (UE_BUILD_SHIPPING || UE_BUILD_TEST)		const bool bIsViewFrozen = false;		const bool bHasViewParent = false;	#else		const bool bIsViewFrozen = Views[0].State && ((FSceneViewState*)Views[0].State)->bIsFrozen;		const bool bHasViewParent = Views[0].State && ((FSceneViewState*)Views[0].State)->HasViewParent();	#endif	const bool bIsOcclusionTesting = DoOcclusionQueries() && (!bIsWireframe || bIsViewFrozen || bHasViewParent);	// Dynamic vertex and index buffers need to be committed before rendering.	FGlobalDynamicVertexBuffer::Get().Commit();	FGlobalDynamicIndexBuffer::Get().Commit();	// Notify the FX system that the scene is about to be rendered.	if (Scene->FXSystem)	{		Scene->FXSystem->PreRender();	}	// Draw the scene pre-pass / early z pass, populating the scene depth buffer and HiZ	RenderPrePass();		// Clear scene color buffer if necessary.	if ( bRequiresRHIClear )	{		ClearView();		// Only clear once.		bRequiresRHIClear = false;	}	// Clear LPVs for all views	if ( IsFeatureLevelSupported(GRHIShaderPlatform, ERHIFeatureLevel::SM5) )	{		ClearLPVs();	}	// only temporarily available after early z pass and until base pass//.........这里部分代码省略.........

	/**	  * Only compile these shaders for post processing domain materials	  */	static bool ShouldCache(EShaderPlatform Platform, const FMaterial* Material)	{		return (Material->GetMaterialDomain() == MD_PostProcess) && IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM4);	}

	/**	  * Makes sure only shaders for materials that are explicitly flagged	  * as 'UsedAsLightFunction' in the Material Editor gets compiled into	  * the shader cache.	  */	static bool ShouldCache(EShaderPlatform Platform, const FMaterial* Material)	{		return Material->IsLightFunction() && IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM3);	}