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03-UnrealEngine/Rendering/RenderingPipeline/UE4 BasePassPixelShader.usf学习笔记.md

@@ -111,3 +111,61 @@ const float3 WaterDiffuseIndirectIlluminance = DiffuseIndirectLighting * PI;// D
 8. Out.MRT[0].rgb  *= ViewPreExposure;
 
 ### 1553：FinalizeVirtualTextureFeedback
+
+# UE5
+
+## Lumen相关
+- GetSkyLighting()
+	- Lumen
+		- GetTranslucencyGIVolumeLighting()
+	- SkyLighting
+		- GetEffectiveSkySHDiffuse()
+			- GetVolumetricLightmapSkyBentNormal()
+			- GetSkyBentNormalAndOcclusion()
+
+**GetSkyLighting()** 演示了采样SkyLight与Lumen的方法。
+
+### SkyLighting
+GetEffectiveSkySHDiffuse()是一个宏，会根据平台指向下面2个函数：
+```c++
+/**   
+ * Computes sky diffuse lighting from the SH irradiance map.    
+ * This has the SH basis evaluation and diffuse convolution weights combined for minimal ALU's - see "Stupid Spherical Harmonics (SH) Tricks"   
+ */  
+float3 GetSkySHDiffuse(float3 Normal)  
+{  
+    float4 NormalVector = float4(Normal, 1.0f);   
+    float3 Intermediate0, Intermediate1, Intermediate2;  
+    Intermediate0.x = dot(SkyIrradianceEnvironmentMap[0], NormalVector);  
+    Intermediate0.y = dot(SkyIrradianceEnvironmentMap[1], NormalVector);  
+    Intermediate0.z = dot(SkyIrradianceEnvironmentMap[2], NormalVector);  
+  
+    float4 vB = NormalVector.xyzz * NormalVector.yzzx;  
+    Intermediate1.x = dot(SkyIrradianceEnvironmentMap[3], vB);  
+    Intermediate1.y = dot(SkyIrradianceEnvironmentMap[4], vB);  
+    Intermediate1.z = dot(SkyIrradianceEnvironmentMap[5], vB);  
+  
+    float vC = NormalVector.x * NormalVector.x - NormalVector.y * NormalVector.y;  
+    Intermediate2 = SkyIrradianceEnvironmentMap[6].xyz * vC;  
+  
+    // max to not get negative colors  
+    return max(0, Intermediate0 + Intermediate1 + Intermediate2);  
+}  
+  
+/**  
+* Computes sky diffuse lighting from the SH irradiance map.  
+* This has the SH basis evaluation and diffuse convolution weights combined for minimal ALU's - see "Stupid Spherical Harmonics (SH) Tricks"  
+* Only does the first 3 components for speed.  
+*/  
+float3 GetSkySHDiffuseSimple(float3 Normal)  
+{  
+    float4 NormalVector = float4(Normal, 1);  
+  
+    float3 Intermediate0;  
+    Intermediate0.x = dot(SkyIrradianceEnvironmentMap[0], NormalVector);  
+    Intermediate0.y = dot(SkyIrradianceEnvironmentMap[1], NormalVector);  
+    Intermediate0.z = dot(SkyIrradianceEnvironmentMap[2], NormalVector);        
+    // max to not get negative colors  
+    return max(0, Intermediate0);  
+}
+```