UE4 随笔记录1

迈不过友情╰ 2023-01-18 06:54 92阅读 0赞

1、蓝图材质转换HLSL代码

*  在蓝图中创建Post Process Material，然后创建SceneTexture，ID选择CustomStencil，如下图：
    
     *  ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoMTUyODUxMTg1ODY_size_16_color_FFFFFF_t_70][]
 *  在材质编辑器下，点击Window->Shader Code->HLSL Code,copy对应代码，保存生成custom.hsls文件（名称随便命名，目的方便描述该文件）。
    
     *  HLSL code 是基于MaterialTemplate.ush(Engine/Shader/Private)进行生成。
     *  如何生成？目前没有深入研究，待后续更新（如果用到）。
 *  对比MaterialTemplate.ush和custom.hsls文件。在VSCode中，左侧目录同时选中两个文件，右键，有compare功能，进行对比哪些是custom.hsls新增的。
    
     *  实际对比，发现有大量的不同出现，然而我们在材质蓝图中，仅仅增加了一个SceneTexture函数，不应该有很多变化。没有深入分析原因，后面用到再研究。
     *  本次研究的重点是如何获得SceneTexture，测试的ID是CustomStencil。而不是Post Process Material如何被使用，因此下面内容会围绕本次重点展开。
     *  在custom.hsls中找出Emissive Color赋值出现的位置：
        
         *  void CalcPixelMaterialInputs(in out FMaterialPixelParameters Parameters, in out FPixelMaterialInputs PixelMaterialInputs)
            
             *  不研究CalcPixelMaterialInputs如何被使用，只研究里面的内容。
         *  EmissiveColor是有两个数值差值的出来。
            
             *  Local0是和SceneTexture相关，深入研究
             *  Material.VectorExpression\[1\].rgb，不是重点，没有深入研究。
         *  关键部分代码
         *      MaterialFloat4 Local0 = SceneTextureLookup(GetDefaultSceneTextureUV(Parameters, 25), 25, false);
                MaterialFloat3 Local1 = erp(Local0.rgba.rgb,Material.VectorExpressions[1].rgb,MaterialFloat(Material.ScalarExpressions[0].x));
                PixelMaterialInputs.EmissiveColor = Local1;
 *  SceneTextureLookup函数介绍
 *      /** Applies an offset to the scene texture lookup and decodes the HDR linear space color. */
        float4 SceneTextureLookup(float2 UV, int SceneTextureIndex, bool bFiltered)
        {
        #if SCENE_TEXTURES_DISABLED
            return float4(0.0f, 0.0f, 0.0f, 0.0f);
        #endif
        
            FScreenSpaceData ScreenSpaceData = GetScreenSpaceData(UV, false);
            switch(SceneTextureIndex)
            {
                // order needs to match to ESceneTextureId
        
                case PPI_SceneColor:
                    return float4(CalcSceneColor(UV), 0);
                case PPI_SceneDepth:
                    return ScreenSpaceData.GBuffer.Depth;
                case PPI_DiffuseColor:
                    return float4(ScreenSpaceData.GBuffer.DiffuseColor, 0);
                case PPI_SpecularColor:
                    return float4(ScreenSpaceData.GBuffer.SpecularColor, 0);
                case PPI_SubsurfaceColor:
                    return IsSubsurfaceModel(ScreenSpaceData.GBuffer.ShadingModelID) ? float4( ExtractSubsurfaceColor(ScreenSpaceData.GBuffer), ScreenSpaceData.GBuffer.CustomData.a ) : ScreenSpaceData.GBuffer.CustomData;
                case PPI_BaseColor:
                    return float4(ScreenSpaceData.GBuffer.BaseColor, 0);
                case PPI_Specular:
                    return ScreenSpaceData.GBuffer.Specular;
                case PPI_Metallic:
                    return ScreenSpaceData.GBuffer.Metallic;
                case PPI_WorldNormal:
                    return float4(ScreenSpaceData.GBuffer.WorldNormal, 0);
                case PPI_SeparateTranslucency:
                    return float4(1, 1, 1, 1);    // todo
                case PPI_Opacity:
                    return ScreenSpaceData.GBuffer.CustomData.a;
                case PPI_Roughness:
                    return ScreenSpaceData.GBuffer.Roughness;
                case PPI_MaterialAO:
                    return ScreenSpaceData.GBuffer.GBufferAO;
                case PPI_CustomDepth:
                    return ScreenSpaceData.GBuffer.CustomDepth;
        #if POST_PROCESS_MATERIAL
                case PPI_PostProcessInput0:
                    return Texture2DSample(PostProcessInput_0_Texture, bFiltered ? PostProcessInput_BilinearSampler : PostProcessInput_0_SharedSampler, UV);
                case PPI_PostProcessInput1:
                    return Texture2DSample(PostProcessInput_1_Texture, bFiltered ? PostProcessInput_BilinearSampler : PostProcessInput_1_SharedSampler, UV);
                case PPI_PostProcessInput2:
                    return Texture2DSample(PostProcessInput_2_Texture, bFiltered ? PostProcessInput_BilinearSampler : PostProcessInput_2_SharedSampler, UV);
                case PPI_PostProcessInput3:
                    return Texture2DSample(PostProcessInput_3_Texture, bFiltered ? PostProcessInput_BilinearSampler : PostProcessInput_3_SharedSampler, UV);
                case PPI_PostProcessInput4:
                    return Texture2DSample(PostProcessInput_4_Texture, bFiltered ? PostProcessInput_BilinearSampler : PostProcessInput_4_SharedSampler, UV);
        #endif // __POST_PROCESS_COMMON__
                case PPI_DecalMask:
                    return 0;  // material compiler will return an error
                case PPI_ShadingModelColor:
                    return float4(GetShadingModelColor(ScreenSpaceData.GBuffer.ShadingModelID), 1);
                case PPI_ShadingModelID:
                    return float4(ScreenSpaceData.GBuffer.ShadingModelID, 0, 0, 0);
                case PPI_AmbientOcclusion:
                    return ScreenSpaceData.AmbientOcclusion;
                case PPI_CustomStencil:
                    return ScreenSpaceData.GBuffer.CustomStencil;
                case PPI_StoredBaseColor:
                    return float4(ScreenSpaceData.GBuffer.StoredBaseColor, 0);
                case PPI_StoredSpecular:
                    return float4(ScreenSpaceData.GBuffer.StoredSpecular.rrr, 0);
        #if POST_PROCESS_MATERIAL
                case PPI_Velocity:
                    return float4(PostProcessVelocityLookup(ConvertToDeviceZ(ScreenSpaceData.GBuffer.Depth), UV), 0, 0);
        #endif
                case PPI_WorldTangent:
                    return float4(ScreenSpaceData.GBuffer.WorldTangent, 0);
                case PPI_Anisotropy:
                    return ScreenSpaceData.GBuffer.Anisotropy;
                default:
                    return float4(0, 0, 0, 0);
            }
        }
    
    GetScreenSpaceData 在DeferredShadingCommon.ush文件中。

// @param UV - UV space in the GBuffer textures (BufferSize resolution)
    FScreenSpaceData GetScreenSpaceData(float2 UV, bool bGetNormalizedNormal = true)
    {
    	FScreenSpaceData Out;
    
    	Out.GBuffer = GetGBufferData(UV, bGetNormalizedNormal);
    	float4 ScreenSpaceAO = Texture2DSampleLevel(SceneTexturesStruct.ScreenSpaceAOTexture, SceneTexturesStruct.ScreenSpaceAOTextureSampler, UV, 0);
    
    	Out.AmbientOcclusion = ScreenSpaceAO.r;
    
    	return Out;
    }

在相同文件内：

// @param UV - UV space in the GBuffer textures (BufferSize resolution)
    FGBufferData GetGBufferData(float2 UV, bool bGetNormalizedNormal = true)
    {
    #if 0 //METAL_MRT_PROFILE
    	// @todo metal mrt: The deferred renderer isn't keeping these in tiled memory all the time - we don't know when this makes sense
    	// versus just sampling a bound resolved texture
    	float4 GBufferA = FramebufferFetchMRT(1);
    	float4 GBufferB = FramebufferFetchMRT(2);
    	float4 GBufferC = FramebufferFetchMRT(3);
    	float4 GBufferD = FramebufferFetchMRT(4);
    	// @todo metal mrt: We can't framebuffer fetch the depth, can we jam it in somewhere?
    	float CustomNativeDepth = 0.5;
    	#if ALLOW_STATIC_LIGHTING
    		float4 GBufferE = FramebufferFetchMRT(5);
    	#else
    		float4 GBufferE = 1;
    	#endif
    #else	
    	float4 GBufferA = Texture2DSampleLevel(SceneTexturesStruct.GBufferATexture, SceneTexturesStruct.GBufferATextureSampler, UV, 0);
    	float4 GBufferB = Texture2DSampleLevel(SceneTexturesStruct.GBufferBTexture, SceneTexturesStruct.GBufferBTextureSampler, UV, 0);
    	float4 GBufferC = Texture2DSampleLevel(SceneTexturesStruct.GBufferCTexture, SceneTexturesStruct.GBufferCTextureSampler, UV, 0);
    	float4 GBufferD = Texture2DSampleLevel(SceneTexturesStruct.GBufferDTexture, SceneTexturesStruct.GBufferDTextureSampler, UV, 0);
    	float CustomNativeDepth = Texture2DSampleLevel(SceneTexturesStruct.CustomDepthTexture, SceneTexturesStruct.CustomDepthTextureSampler, UV, 0).r;
    
    #if FEATURE_LEVEL >= FEATURE_LEVEL_SM4
    	int2 IntUV = (int2)trunc(UV * View.BufferSizeAndInvSize.xy);
    	uint CustomStencil = SceneTexturesStruct.CustomStencilTexture.Load(int3(IntUV, 0)) STENCIL_COMPONENT_SWIZZLE;
    #else
    	uint CustomStencil = 0;
    #endif
    
    	#if ALLOW_STATIC_LIGHTING
    		float4 GBufferE = Texture2DSampleLevel(SceneTexturesStruct.GBufferETexture, SceneTexturesStruct.GBufferETextureSampler, UV, 0);
    	#else
    		float4 GBufferE = 1;
    	#endif
    
    	#if WRITES_VELOCITY_TO_GBUFFER
    		float4 GBufferVelocity = Texture2DSampleLevel(SceneTexturesStruct.GBufferVelocityTexture, SceneTexturesStruct.GBufferVelocityTextureSampler, UV, 0);
    	#else
    		float4 GBufferVelocity = 0;
    	#endif
    #endif
    
    	float SceneDepth = CalcSceneDepth(UV);
    	
    	return DecodeGBufferData(GBufferA, GBufferB, GBufferC, GBufferD, GBufferE, GBufferVelocity, CustomNativeDepth, CustomStencil, SceneDepth, bGetNormalizedNormal, CheckerFromSceneColorUV(UV));
    }

在相同文件里：

/** Populates FGBufferData */
    // @param bChecker High frequency Checkerboard pattern computed with one of the CheckerFrom.. functions, todo: profile if float 0/1 would be better (need to make sure it's 100% the same)
    FGBufferData DecodeGBufferData(
    	float4 InGBufferA,
    	float4 InGBufferB,
    	float4 InGBufferC,
    	float4 InGBufferD,
    	float4 InGBufferE,
    	float4 InGBufferVelocity,
    	float CustomNativeDepth,
    	uint CustomStencil,
    	float SceneDepth,
    	bool bGetNormalizedNormal,
    	bool bChecker)
    {
    	FGBufferData GBuffer;
    
    	GBuffer.WorldNormal = DecodeNormal( InGBufferA.xyz );
    	if(bGetNormalizedNormal)
    	{
    		GBuffer.WorldNormal = normalize(GBuffer.WorldNormal);
    	}
    
    	GBuffer.PerObjectGBufferData = InGBufferA.a;  
    	GBuffer.Metallic	= InGBufferB.r;
    	GBuffer.Specular	= InGBufferB.g;
    	GBuffer.Roughness	= InGBufferB.b;
    	// Note: must match GetShadingModelId standalone function logic
    	// Also Note: SimpleElementPixelShader directly sets SV_Target2 ( GBufferB ) to indicate unlit.
    	// An update there will be required if this layout changes.
    	GBuffer.ShadingModelID = DecodeShadingModelId(InGBufferB.a);
    	GBuffer.SelectiveOutputMask = DecodeSelectiveOutputMask(InGBufferB.a);
    
    	GBuffer.BaseColor = DecodeBaseColor(InGBufferC.rgb);
    
    #if ALLOW_STATIC_LIGHTING
    	GBuffer.GBufferAO = 1;
    	GBuffer.IndirectIrradiance = DecodeIndirectIrradiance(InGBufferC.a);
    #else
    	GBuffer.GBufferAO = InGBufferC.a;
    	GBuffer.IndirectIrradiance = 1;
    #endif
    
    	GBuffer.CustomData = !(GBuffer.SelectiveOutputMask & SKIP_CUSTOMDATA_MASK) ? InGBufferD : 0;
    
    	GBuffer.PrecomputedShadowFactors = !(GBuffer.SelectiveOutputMask & SKIP_PRECSHADOW_MASK) ? InGBufferE :  ((GBuffer.SelectiveOutputMask & ZERO_PRECSHADOW_MASK) ? 0 :  1);
    	GBuffer.CustomDepth = ConvertFromDeviceZ(CustomNativeDepth);
    	GBuffer.CustomStencil = CustomStencil;
    	GBuffer.Depth = SceneDepth;
    
    	GBuffer.StoredBaseColor = GBuffer.BaseColor;
    	GBuffer.StoredMetallic = GBuffer.Metallic;
    	GBuffer.StoredSpecular = GBuffer.Specular;
    
    	FLATTEN
    	if( GBuffer.ShadingModelID == SHADINGMODELID_EYE )
    	{
    		GBuffer.Metallic = 0.0;
    #if IRIS_NORMAL
    		GBuffer.Specular = 0.25;
    #endif
    	}
    
    	// derived from BaseColor, Metalness, Specular
    	{
    		GBuffer.SpecularColor = ComputeF0(GBuffer.Specular, GBuffer.BaseColor, GBuffer.Metallic);
    
    		if (UseSubsurfaceProfile(GBuffer.ShadingModelID))
    		{
    			AdjustBaseColorAndSpecularColorForSubsurfaceProfileLighting(GBuffer.BaseColor, GBuffer.SpecularColor, GBuffer.Specular, bChecker);
    		}
    
    		GBuffer.DiffuseColor = GBuffer.BaseColor - GBuffer.BaseColor * GBuffer.Metallic;
    
    		#if USE_DEVELOPMENT_SHADERS
    		{
    			// this feature is only needed for development/editor - we can compile it out for a shipping build (see r.CompileShadersForDevelopment cvar help)
    			GBuffer.DiffuseColor = GBuffer.DiffuseColor * View.DiffuseOverrideParameter.www + View.DiffuseOverrideParameter.xyz;
    			GBuffer.SpecularColor = GBuffer.SpecularColor * View.SpecularOverrideParameter.w + View.SpecularOverrideParameter.xyz;
    		}
    		#endif //USE_DEVELOPMENT_SHADERS
    	}
    
    	GBuffer.Velocity = !(GBuffer.SelectiveOutputMask & SKIP_VELOCITY_MASK) ? InGBufferVelocity : 0;
    
    	return GBuffer;
    }

回归到CustomStencil：

#if FEATURE_LEVEL >= FEATURE_LEVEL_SM4
    	int2 IntUV = (int2)trunc(UV * View.BufferSizeAndInvSize.xy);
    	uint CustomStencil = SceneTexturesStruct.CustomStencilTexture.Load(int3(IntUV, 0)) STENCIL_COMPONENT_SWIZZLE;
    #else
    	uint CustomStencil = 0;
    #endif

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