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03-UnrealEngine/卡通渲染相关资料/渲染功能/ToonReflection&GI控制/ToonReflection.md

@@ -46,7 +46,246 @@ rating: ⭐
 	3. 结果赋予给FRDGTextureRef ReflectionsColor。
 - 执行完上述反射方法后，最后执行`AddSkyReflectionPass()`
 
-`FReflectionEnvironmentSkyLightingPS`位于/Engine/Private/ReflectionEnvironmentPixelShader.usf的ReflectionEnvironmentSkyLighting()。
+FReflectionEnvironmentSkyLightingPS位于/Engine/Private/ReflectionEnvironmentPixelShader.usf的`ReflectionEnvironmentSkyLighting()`。
 
+### ReflectionEnvironmentSkyLighting
+```c++
+void ReflectionEnvironmentSkyLighting(
+	in float4 SvPosition : SV_Position,
+	out float4 OutColor : SV_Target0
+#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
+	, out float3 OutOpaqueRoughRefractionSceneColor : SV_Target1
+	, out float3 OutSubSurfaceSceneColor : SV_Target2
+#endif
+	)
+{
+	ResolvedView = ResolveView();
+	//计算获去BufferUV、ScreenPosition
+	uint2 PixelPos = SvPosition.xy;
+	float2 BufferUV = SvPositionToBufferUV(SvPosition);
+	float2 ScreenPosition = SvPositionToScreenPosition(SvPosition).xy;
+	
+	OutColor = 0.0f;
+#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
+	OutOpaqueRoughRefractionSceneColor = 0.0f;
+	OutSubSurfaceSceneColor = 0.0f;
+#endif
+
+#if STRATA_ENABLED
+...
+...
+#else // STRATA_ENABLED
+
+	// Sample scene textures.
+	FGBufferData GBuffer = GetGBufferDataFromSceneTextures(BufferUV);
+
+	uint ShadingModelID = GBuffer.ShadingModelID;
+	const bool bUnlitMaterial = ShadingModelID == SHADINGMODELID_UNLIT;
+
+	float3 DiffuseColor = GBuffer.DiffuseColor;
+	float3 SpecularColor = GBuffer.SpecularColor;
+	RemapClearCoatDiffuseAndSpecularColor(GBuffer, ScreenPosition, DiffuseColor, SpecularColor);//针对清漆材质进行Diffuse颜色与Specular颜色重新映射
+
+	// Sample the ambient occlusion that is dynamically generated every frame.
+	float AmbientOcclusion = AmbientOcclusionTexture.SampleLevel(AmbientOcclusionSampler, BufferUV, 0).r;
+
+	float3 BentNormal = GBuffer.WorldNormal;
+#if APPLY_SKY_SHADOWING
+	{
+		BentNormal = UpsampleDFAO(BufferUV, GBuffer.Depth, GBuffer.WorldNormal);
+	}
+#endif
+
+#if ENABLE_DYNAMIC_SKY_LIGHT
+	BRANCH
+	if (!bUnlitMaterial) // Only light pixels marked as lit //Unlit材质不会计算动态天光GI的效果。
+	{
+		float3 TranslatedWorldPosition = mul(float4(GetScreenPositionForProjectionType(ScreenPosition, GBuffer.Depth), GBuffer.Depth, 1), View.ScreenToTranslatedWorld).xyz;
+		const float CloudVolumetricAOShadow = GetCloudVolumetricAOShadow(TranslatedWorldPosition);//从体积云 VolumetricCloudShadowMapTexture中取得ShadowFrontDepthKm、MaxOpticalDepth，MeanExtinction，最终计算出体积云阴影。UE5.3该函数没有启用。
+
+		float3 SkyLighting = CloudVolumetricAOShadow * SkyLightDiffuse(GBuffer, AmbientOcclusion, BufferUV, ScreenPosition, BentNormal, DiffuseColor);
+
+		FLightAccumulator LightAccumulator = (FLightAccumulator)0;
+		const bool bNeedsSeparateSubsurfaceLightAccumulation = UseSubsurfaceProfile(ShadingModelID);
+		LightAccumulator_Add(LightAccumulator, SkyLighting, SkyLighting, 1.0f, bNeedsSeparateSubsurfaceLightAccumulation);
+		OutColor = LightAccumulator_GetResult(LightAccumulator);
+	}
+
+#endif // ENABLE_DYNAMIC_SKY_LIGHT 
+
+	BRANCH
+	if (!bUnlitMaterial && ShadingModelID != SHADINGMODELID_HAIR)//
+	{
+		OutColor.xyz += ReflectionEnvironment(GBuffer, AmbientOcclusion, BufferUV, ScreenPosition, SvPosition, BentNormal, SpecularColor, ShadingModelID);
+	}
+
+#endif // STRATA_ENABLED
+}
+
+
+```
+
+### SkyLightDiffuse
+1. 计算float3 SkyLightingNormal、FSkyLightVisibilityData SkyVisData。
+2. 计算Normal、ViewVector、NoV。
+3. 针对制定ShadingModel进行额外计算：
+	1. SHADINGMODELID_TWOSIDED_FOLIAGE：使用Normal反向量取得SkySHDiffuse，在乘以SubsurfaceColor、SkyVisData.SkyDiffuseLookUpMul后累加到结果上。
+	2. SHADINGMODELID_SUBSURFACE、SHADINGMODELID_PREINTEGRATED_SKIN：从GBuffer中提取SubsurfaceColor并累加到结果上。
+	3. SHADINGMODELID_CLOTH：从GBuffer中提取ClothFuzz(SubsurfaceColor)乘以CustomData.a，并累加到结果上。
+	4. SHADINGMODELID_HAIR：
+		1. DiffuseColor = EvaluateEnvHair(GBuffer, V, N, L);
+		2. SkyVisData.SkyDiffuseLookUpNormal = L;
+		3. DiffuseWeight = 1.0f;
+4. 调用GetSkySHDiffuse()计算天光光照效果。GetSkySHDiffuse()本质是采样球谐贴图，来获得天光GI结果。
+
+### ReflectionEnvironment
+```c++
+float3 ReflectionEnvironment(FGBufferData GBuffer, float AmbientOcclusion, float2 BufferUV, float2 ScreenPosition, float4 SvPosition, float3 BentNormal, float3 SpecularColor, uint ShadingModelID)
+{
+	float4 Color = float4(0, 0, 0, 1);
+
+	float IndirectIrradiance = GBuffer.IndirectIrradiance;
+	
+#if ENABLE_SKY_LIGHT && ALLOW_STATIC_LIGHTING
+	BRANCH
+	// Add in diffuse contribution from dynamic skylights so reflection captures will have something to mix with
+	if (ReflectionStruct.SkyLightParameters.y > 0 && ReflectionStruct.SkyLightParameters.z > 0)
+	{
+		//如果开启天光、并且开启静态关照。会在这里采样SkySH，以此累加间接照明。
+		IndirectIrradiance += GetDynamicSkyIndirectIrradiance(BentNormal, GBuffer.WorldNormal);
+	}
+#endif
+
+	//计算反射Vector、WorldNormal、ViewVector
+	float3 TranslatedWorldPosition = mul(float4(GetScreenPositionForProjectionType(ScreenPosition, GBuffer.Depth), GBuffer.Depth, 1), View.ScreenToTranslatedWorld).xyz;
+	float3 CameraToPixel = normalize(TranslatedWorldPosition - View.TranslatedWorldCameraOrigin);
+	float3 ReflectionVector = reflect(CameraToPixel, GBuffer.WorldNormal);
+    float3 V = -CameraToPixel;
+	float3 N = GBuffer.WorldNormal;
+
+	const float3 SavedTopLayerNormal = N;
+
+#if SUPPORTS_ANISOTROPIC_MATERIALS
+	ModifyGGXAnisotropicNormalRoughness(GBuffer.WorldTangent, GBuffer.Anisotropy, GBuffer.Roughness, N, V);
+#endif
+
+	float3 R = 2 * dot( V, N ) * N - V;
+	float NoV = saturate( dot( N, V ) );
+
+	// Point lobe in off-specular peak direction
+	R = GetOffSpecularPeakReflectionDir(N, R, GBuffer.Roughness);
+
+	// 采样 SSR, planar reflections, RT reflections or Lumen 反射结果。
+	float4 ReflectionInput = Texture2DSample(ReflectionTexture, ReflectionTextureSampler, BufferUV);
+	Color = CompositeReflections(ReflectionInput, BufferUV, GBuffer.Roughness, ShadingModelID);//Color = float4(ReflectionInput.rgb, 1 - ReflectionInput.a)
+
+#if RAY_TRACED_REFLECTIONS
+	float4 SavedColor = Color;	// When a clear coat material is encountered, we save the reflection buffer color for it to not be affected by operations.
+#endif
+	if(GBuffer.ShadingModelID == SHADINGMODELID_CLEAR_COAT )
+	{
+#if RAY_TRACED_REFLECTIONS
+		Color = float4(0, 0, 0, 1); // Clear coat reflection is expected to be computed on a black background
+#endif
+		const float ClearCoat = GBuffer.CustomData.x;
+		Color = lerp( Color, float4(0,0,0,1), ClearCoat );
+
+#if CLEAR_COAT_BOTTOM_NORMAL
+		const float2 oct1 = ((float2(GBuffer.CustomData.a, GBuffer.CustomData.z) * 4) - (512.0/255.0)) + UnitVectorToOctahedron(GBuffer.WorldNormal);
+		const float3 ClearCoatUnderNormal = OctahedronToUnitVector(oct1);
+
+		const float3 BottomEffectiveNormal = ClearCoatUnderNormal;			
+		R = 2 * dot( V, ClearCoatUnderNormal ) * ClearCoatUnderNormal - V;
+#endif
+	}
+
+	float AO = GBuffer.GBufferAO * AmbientOcclusion;//AmbientOcclusion为SSAO或者RTAO或者DFAO或者Lumen……
+	float RoughnessSq = GBuffer.Roughness * GBuffer.Roughness;
+	float SpecularOcclusion = GetSpecularOcclusion(NoV, RoughnessSq, AO);
+	Color.a *= SpecularOcclusion;
+
+#if FEATURE_LEVEL >= FEATURE_LEVEL_SM5
+	float2 LocalPosition = SvPosition.xy - View.ViewRectMin.xy;
+
+	uint GridIndex = ComputeLightGridCellIndex(uint2(LocalPosition.x, LocalPosition.y), GBuffer.Depth);
+	uint NumCulledEntryIndex = (ForwardLightData.NumGridCells + GridIndex) * NUM_CULLED_LIGHTS_GRID_STRIDE;
+	uint NumCulledReflectionCaptures = min(ForwardLightData.NumCulledLightsGrid[NumCulledEntryIndex + 0], ForwardLightData.NumReflectionCaptures);
+	uint DataStartIndex = ForwardLightData.NumCulledLightsGrid[NumCulledEntryIndex + 1];
+#else
+	uint DataStartIndex = 0;
+	uint NumCulledReflectionCaptures = 0;
+#endif
+
+	const FBxDFEnergyTerms EnergyTerms = ComputeGGXSpecEnergyTerms(GBuffer.Roughness, NoV, GBuffer.SpecularColor);
+
+	//常规反射 或 底层清漆 光照计算
+	//Top of regular reflection or bottom layer of clear coat.
+	Color.rgb += View.PreExposure * GatherRadiance(Color.a, TranslatedWorldPosition, R, GBuffer.Roughness, BentNormal, IndirectIrradiance, GBuffer.ShadingModelID, NumCulledReflectionCaptures, DataStartIndex);
+
+	BRANCH
+	if( GBuffer.ShadingModelID == SHADINGMODELID_CLEAR_COAT)
+	{
+		const float ClearCoat			= GBuffer.CustomData.x;
+		const float ClearCoatRoughness	= GBuffer.CustomData.y;
+
+		// Restore saved values needed for the top layer.
+		GBuffer.WorldNormal = SavedTopLayerNormal;
+		// Recompute some values unaffected by anistropy for the top layer
+		N = GBuffer.WorldNormal;
+		R = 2 * dot(V, N) * N - V;
+		NoV = saturate(dot(N, V));
+		R = GetOffSpecularPeakReflectionDir(N, R, ClearCoatRoughness);
+
+		// TODO EnvBRDF should have a mask param
+		#if USE_ENERGY_CONSERVATION
+		Color.rgb *= EnergyTerms.E * (1 - ClearCoat);
+		#else
+		// Hack: Ensures when clear coat is >0, grazing angle does not get too much energy, 
+		//       but preserve response at normal incidence 
+		float2 AB = PreIntegratedGF.SampleLevel(PreIntegratedGFSampler, float2(NoV, GBuffer.Roughness), 0).rg;
+		Color.rgb *= SpecularColor * AB.x + AB.y * saturate(50 * SpecularColor.g) * (1 - ClearCoat);
+		#endif
+
+		// F_Schlick
+		const float CoatF0 = 0.04f;
+		#if USE_ENERGY_CONSERVATION
+		float F = ComputeGGXSpecEnergyTerms(ClearCoatRoughness, NoV, CoatF0).E.x;
+		#else
+		float F = EnvBRDF(CoatF0, ClearCoatRoughness, NoV).x;
+		#endif
+
+		F *= ClearCoat;
+			
+		float LayerAttenuation = (1 - F);		
+		Color.rgb *= LayerAttenuation;
+		Color.a = F;
+		
+#if !RAY_TRACED_REFLECTIONS	
+		Color.rgb += ReflectionInput.rgb * F;
+		Color.a *= 1 - ReflectionInput.a;
+#endif
+			
+		Color.a *= SpecularOcclusion;
+
+		float3 TopLayerR = 2 * dot( V, N ) * N - V;
+		Color.rgb += View.PreExposure * GatherRadiance(Color.a, TranslatedWorldPosition, TopLayerR, ClearCoatRoughness, BentNormal, IndirectIrradiance, GBuffer.ShadingModelID, NumCulledReflectionCaptures, DataStartIndex);
+
+	#if RAY_TRACED_REFLECTIONS
+		Color.rgb = SavedColor.rgb +  Color.rgb * SavedColor.a; // Compose default clear coat reflection over regular refelction (using Premultiplied alpha where SaveColor.a=transmittance)
+	#endif
+	}
+	else
+	{
+		#if USE_ENERGY_CONSERVATION
+		Color.rgb *= EnergyTerms.E;
+		#else
+		Color.rgb *= EnvBRDF( SpecularColor, GBuffer.Roughness, NoV );
+		#endif
+	}
+
+	// Transform NaNs to black, transform negative colors to black.
+	return -min(-Color.rgb, 0.0);
+}
+```
 ## DiffuseIndirectComposite
 位于IndirectLightRendering.cpp的`RenderDiffuseIndirectAndAmbientOcclusion()`