vault backup: 2025-02-13 13:48:03

03-UnrealEngine/Rendering/RenderingPipeline/Lighting/Lighting.md

@@ -455,6 +455,61 @@ void DeferredLightPixelMain(
 #endif
 ```
 
+#### GetLightAttenuationFromShadow() => GetPerPixelLightAttenuation()
+原文：https://zhuanlan.zhihu.com/p/23216110797
+有提到阴影模糊问题。
+ FDeferredLightPS::FParameters GetDeferredLightPSParameters()可以看到该Sampler的模式是Point模式。
+```c++
+float4 GetPerPixelLightAttenuation(float2 UV)
+{
+	return DecodeLightAttenuation(Texture2DSampleLevel(LightAttenuationTexture, LightAttenuationTextureSampler, UV, 0));
+}
+```
+
+之后可以仿照GetPerPixelLightAttenuation写一个针对ToonShadow的函数：
+```c++
+//对卡通阴影进行降采样抗锯齿  
+float4 GetPerPixelLightAttenuationToonAA(float2 UV)  
+{  
+    int texture_x, texture_y;  
+    LightAttenuationTexture.GetDimensions(texture_x, texture_y);  
+
+    float2 texelSize = float2(1.0 / texture_x, 1.0 / texture_y);  
+
+    float2 sampleOffsets[4] = {  
+       float2(-1.5,  0.5),  
+       float2( 0.5,  0.5),  
+       float2(-1.5, -1.5),  
+       float2( 0.5, -1.5)  
+    };  
+
+    float4 shadowSum = float4(0,0,0,0);  
+    for (int i = 0; i < 4; i++)  
+    {  
+       float2 sampleUV = UV + sampleOffsets[i] * texelSize;  
+       shadowSum += DecodeLightAttenuation(Texture2DSampleLevel(LightAttenuationTexture, LightAttenuationTextureSampler_Toon, sampleUV, 0));  
+    }  
+    return shadowSum * 0.25;  
+}
+
+//获取卡通灯光衰减  
+float4 GetLightAttenuationFromShadowToonAA(in FInputParams InputParams, float SceneDepth, float3 TranslatedWorldPosition)  
+{  
+    float4 LightAttenuation = float4(1, 1, 1, 1);  
+
+#if USE_VIRTUAL_SHADOW_MAP_MASK  
+    if (VirtualShadowMapId != INDEX_NONE)  
+    {       
+	    float ShadowMask = GetVirtualShadowMapMaskForLight(ShadowMaskBits[InputParams.PixelPos], uint2(InputParams.PixelPos), SceneDepth, VirtualShadowMapId, TranslatedWorldPosition);       
+	    return ShadowMask.xxxx;  
+    }else  
+#endif  
+    {  
+	    return GetPerPixelLightAttenuationToonAA(InputParams.ScreenUV);  
+    }  
+}
+```
+
 ### GetDynamicLighting() => GetDynamicLightingSplit()
 ```c++
 FDeferredLightingSplit GetDynamicLightingSplit(
@@ -700,7 +755,7 @@ void GetShadowTerms(float SceneDepth, half4 PrecomputedShadowFactors, uint Shadi
 		}
 	}
 
-#if SUPPORT_CONTACT_SHADOWS
+#if SUPPORT_CONTACT_SHADOWS //接触阴影相关逻辑
 
 #if STRATA_ENABLED == 0
 	if (LightData.ShadowedBits < 2 && (ShadingModelID == SHADINGMODELID_HAIR))