819 lines
33 KiB
Markdown
819 lines
33 KiB
Markdown
---
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title: Untitled
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date: 2025-02-11 11:30:34
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excerpt:
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tags:
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rating: ⭐
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---
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# FSortedLightSetSceneInfo
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有序的光源集合相关定义：
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```c++
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/** Data for a simple dynamic light. */
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class FSimpleLightEntry
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{
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public:
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FVector3f Color;
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float Radius;
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float Exponent;
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float InverseExposureBlend = 0.0f;
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float VolumetricScatteringIntensity;
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bool bAffectTranslucency;
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};
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struct FSortedLightSceneInfo
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{
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union
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{
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struct
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{
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// Note: the order of these members controls the light sort order!
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// Currently bHandledByLumen is the MSB and LightType is LSB /** The type of light. */ uint32 LightType : LightType_NumBits;
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/** Whether the light has a texture profile. */
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uint32 bTextureProfile : 1;
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/** Whether the light uses a light function. */
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uint32 bLightFunction : 1;
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/** Whether the light uses lighting channels. */
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uint32 bUsesLightingChannels : 1;
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/** Whether the light casts shadows. */
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uint32 bShadowed : 1;
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/** Whether the light is NOT a simple light - they always support tiled/clustered but may want to be selected separately. */
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uint32 bIsNotSimpleLight : 1;
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/* We want to sort the lights that write into the packed shadow mask (when enabled) to the front of the list so we don't waste slots in the packed shadow mask. */
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uint32 bDoesNotWriteIntoPackedShadowMask : 1;
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/**
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* True if the light doesn't support clustered deferred, logic is inverted so that lights that DO support clustered deferred will sort first in list
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* Super-set of lights supporting tiled, so the tiled lights will end up in the first part of this range.
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*/
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uint32 bClusteredDeferredNotSupported : 1;
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/** Whether the light should be handled by Lumen's Final Gather, these will be sorted to the end so they can be skipped */
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uint32 bHandledByLumen : 1;
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} Fields;
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/** Sort key bits packed into an integer. */
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int32 Packed;
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} SortKey;
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const FLightSceneInfo* LightSceneInfo;
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int32 SimpleLightIndex;
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/** Initialization constructor. */
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explicit FSortedLightSceneInfo(const FLightSceneInfo* InLightSceneInfo)
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: LightSceneInfo(InLightSceneInfo),
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SimpleLightIndex(-1)
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{
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SortKey.Packed = 0;
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SortKey.Fields.bIsNotSimpleLight = 1;
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}
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explicit FSortedLightSceneInfo(int32 InSimpleLightIndex)
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: LightSceneInfo(nullptr),
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SimpleLightIndex(InSimpleLightIndex)
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{
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SortKey.Packed = 0;
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SortKey.Fields.bIsNotSimpleLight = 0;
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}};
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/**
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* Stores info about sorted lights and ranges.
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* The sort-key in FSortedLightSceneInfo gives rise to the following order:
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* [SimpleLights,Clustered,UnbatchedLights,LumenLights] * Note that some shadowed lights can be included in the clustered pass when virtual shadow maps and one pass projection are used. */struct FSortedLightSetSceneInfo
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{
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int32 SimpleLightsEnd;
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int32 ClusteredSupportedEnd;
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/** First light with shadow map or */
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int32 UnbatchedLightStart;
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int32 LumenLightStart;
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FSimpleLightArray SimpleLights;
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TArray<FSortedLightSceneInfo, SceneRenderingAllocator> SortedLights;
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};
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```
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## 开始获取有序光源集合
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UE的光源分配由`FDeferredShadingSceneRenderer::Render`内的`bComputeLightGrid`变量决定的，bComputeLightGrid的赋值逻辑如下：
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```c++
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void FDeferredShadingSceneRenderer::Render(FRHICommandListImmediate& RHICmdList) {
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...
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bool bComputeLightGrid = false;
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if (RendererOutput == ERendererOutput::FinalSceneColor)
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{
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if (bUseVirtualTexturing)
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{
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// Note, should happen after the GPU-Scene update to ensure rendering to runtime virtual textures is using the correctly updated scene
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FVirtualTextureSystem::Get().EndUpdate(GraphBuilder, MoveTemp(VirtualTextureUpdater), FeatureLevel);
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}
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#if RHI_RAYTRACING
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GatherRayTracingWorldInstancesForView(GraphBuilder, ReferenceView, RayTracingScene, InitViewTaskDatas.RayTracingRelevantPrimitives);
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#endif // RHI_RAYTRACING
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bool bAnyLumenEnabled = false;
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{
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if (bUseGBuffer)
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{
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bComputeLightGrid = bRenderDeferredLighting;
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}
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else
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{
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bComputeLightGrid = ViewFamily.EngineShowFlags.Lighting;
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}
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for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)
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{
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FViewInfo& View = Views[ViewIndex];
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bAnyLumenEnabled = bAnyLumenEnabled
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|| GetViewPipelineState(View).DiffuseIndirectMethod == EDiffuseIndirectMethod::Lumen
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|| GetViewPipelineState(View).ReflectionsMethod == EReflectionsMethod::Lumen;
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}
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bComputeLightGrid |= (
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ShouldRenderVolumetricFog() ||
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VolumetricCloudWantsToSampleLocalLights(Scene, ViewFamily.EngineShowFlags) ||
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ViewFamily.ViewMode != VMI_Lit ||
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bAnyLumenEnabled ||
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VirtualShadowMapArray.IsEnabled() ||
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ShouldVisualizeLightGrid());
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}
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}
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...
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}
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```
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获取有序的光源集合
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```c++
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void FDeferredShadingSceneRenderer::Render(FRHICommandListImmediate& RHICmdList) {
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...
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// 有序的光源集合.
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FSortedLightSetSceneInfo& SortedLightSet = *GraphBuilder.AllocObject<FSortedLightSetSceneInfo>();
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{
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RDG_CSV_STAT_EXCLUSIVE_SCOPE(GraphBuilder, SortLights);
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RDG_GPU_STAT_SCOPE(GraphBuilder, SortLights);
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ComputeLightGridOutput = GatherLightsAndComputeLightGrid(GraphBuilder, bComputeLightGrid, SortedLightSet);
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}
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...
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}
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```
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PS. 简单光源都可以被分块或分簇渲染，但对于非简单光源，只有满足以下条件的光源才可被分块或分簇渲染：
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- 没有使用光源的附加特性（TextureProfile、LightFunction、LightingChannel）。
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- 没有开启阴影。
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- 非平行光或矩形光。
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另外，是否支持分块渲染，还需要光源场景代理的`IsTiledDeferredLightingSupported`返回true，长度为0的点光源才支持分块渲染。
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## GatherLightsAndComputeLightGrid
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```c++
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FComputeLightGridOutput FDeferredShadingSceneRenderer::GatherLightsAndComputeLightGrid(FRDGBuilder& GraphBuilder, bool bNeedLightGrid, FSortedLightSetSceneInfo& SortedLightSet)
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{
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SCOPED_NAMED_EVENT(GatherLightsAndComputeLightGrid, FColor::Emerald);
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FComputeLightGridOutput Result = {};
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bool bShadowedLightsInClustered = ShouldUseClusteredDeferredShading()
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&& CVarVirtualShadowOnePassProjection.GetValueOnRenderThread()
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&& VirtualShadowMapArray.IsEnabled();
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const bool bUseLumenDirectLighting = ShouldRenderLumenDirectLighting(Scene, Views[0]);
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GatherAndSortLights(SortedLightSet, bShadowedLightsInClustered, bUseLumenDirectLighting);
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if (!bNeedLightGrid)
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{
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SetDummyForwardLightUniformBufferOnViews(GraphBuilder, ShaderPlatform, Views);
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return Result;
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}
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bool bAnyViewUsesForwardLighting = false;
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bool bAnyViewUsesLumen = false;
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for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)
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{
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const FViewInfo& View = Views[ViewIndex];
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bAnyViewUsesForwardLighting |= View.bTranslucentSurfaceLighting || ShouldRenderVolumetricFog() || View.bHasSingleLayerWaterMaterial || VolumetricCloudWantsToSampleLocalLights(Scene, ViewFamily.EngineShowFlags) || ShouldVisualizeLightGrid();
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bAnyViewUsesLumen |= GetViewPipelineState(View).DiffuseIndirectMethod == EDiffuseIndirectMethod::Lumen || GetViewPipelineState(View).ReflectionsMethod == EReflectionsMethod::Lumen;
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}
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const bool bCullLightsToGrid = GLightCullingQuality
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&& (IsForwardShadingEnabled(ShaderPlatform) || bAnyViewUsesForwardLighting || IsRayTracingEnabled() || ShouldUseClusteredDeferredShading() ||
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bAnyViewUsesLumen || ViewFamily.EngineShowFlags.VisualizeMeshDistanceFields || VirtualShadowMapArray.IsEnabled());
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// Store this flag if lights are injected in the grids, check with 'AreLightsInLightGrid()'
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bAreLightsInLightGrid = bCullLightsToGrid;
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Result = ComputeLightGrid(GraphBuilder, bCullLightsToGrid, SortedLightSet);
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return Result;
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}
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```
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- GatherAndSortLights：收集与排序当前场景中所有的可见光源（当前View）。
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- ComputeLightGrid：是在锥体空间（frustum space）裁剪局部光源和反射探针到3D格子中，构建每个视图相关的光源列表和格子。
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# RenderLights() -> RenderLight()
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## InternalRenderLight()
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## DeferredLightVertexShaders
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```c++
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// 输入参数.
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struct FInputParams
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{
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float2 PixelPos;
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float4 ScreenPosition;
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float2 ScreenUV;
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float3 ScreenVector;
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};
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// 派生参数.
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struct FDerivedParams
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{
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float3 CameraVector;
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float3 WorldPosition;
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};
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// 获取派生参数.
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FDerivedParams GetDerivedParams(in FInputParams Input, in float SceneDepth)
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{
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FDerivedParams Out;
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#if LIGHT_SOURCE_SHAPE > 0
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// With a perspective projection, the clip space position is NDC * Clip.w
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// With an orthographic projection, clip space is the same as NDC
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float2 ClipPosition = Input.ScreenPosition.xy / Input.ScreenPosition.w * (View.ViewToClip[3][3] < 1.0f ? SceneDepth : 1.0f);
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Out.WorldPosition = mul(float4(ClipPosition, SceneDepth, 1), View.ScreenToWorld).xyz;
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Out.CameraVector = normalize(Out.WorldPosition - View.WorldCameraOrigin);
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#else
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Out.WorldPosition = Input.ScreenVector * SceneDepth + View.WorldCameraOrigin;
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Out.CameraVector = normalize(Input.ScreenVector);
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#endif
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return Out;
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}
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Texture2D<uint> LightingChannelsTexture;
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uint GetLightingChannelMask(float2 UV)
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{
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uint2 IntegerUV = UV * View.BufferSizeAndInvSize.xy;
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return LightingChannelsTexture.Load(uint3(IntegerUV, 0)).x;
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}
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float GetExposure()
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{
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return View.PreExposure;
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}
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```
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向往文章中的SetupLightDataForStandardDeferred()变为InitDeferredLightFromUniforms()。位于LightDataUniform.ush。
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```c++
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FDeferredLightData InitDeferredLightFromUniforms(uint InLightType)
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{
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const bool bIsRadial = InLightType != LIGHT_TYPE_DIRECTIONAL;
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FDeferredLightData Out;
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Out.TranslatedWorldPosition = GetDeferredLightTranslatedWorldPosition();
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Out.InvRadius = DeferredLightUniforms.InvRadius;
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Out.Color = DeferredLightUniforms.Color;
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Out.FalloffExponent = DeferredLightUniforms.FalloffExponent;
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Out.Direction = DeferredLightUniforms.Direction;
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Out.Tangent = DeferredLightUniforms.Tangent;
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Out.SpotAngles = DeferredLightUniforms.SpotAngles;
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Out.SourceRadius = DeferredLightUniforms.SourceRadius;
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Out.SourceLength = bIsRadial ? DeferredLightUniforms.SourceLength : 0;
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Out.SoftSourceRadius = DeferredLightUniforms.SoftSourceRadius;
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Out.SpecularScale = DeferredLightUniforms.SpecularScale;
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Out.ContactShadowLength = abs(DeferredLightUniforms.ContactShadowLength);
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Out.ContactShadowLengthInWS = DeferredLightUniforms.ContactShadowLength < 0.0f;
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Out.ContactShadowCastingIntensity = DeferredLightUniforms.ContactShadowCastingIntensity;
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Out.ContactShadowNonCastingIntensity = DeferredLightUniforms.ContactShadowNonCastingIntensity;
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Out.DistanceFadeMAD = DeferredLightUniforms.DistanceFadeMAD;
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Out.ShadowMapChannelMask = DeferredLightUniforms.ShadowMapChannelMask;
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Out.ShadowedBits = DeferredLightUniforms.ShadowedBits;
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Out.bInverseSquared = bIsRadial && DeferredLightUniforms.FalloffExponent == 0; // Directional lights don't use 'inverse squared attenuation'
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Out.bRadialLight = bIsRadial;
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Out.bSpotLight = InLightType == LIGHT_TYPE_SPOT;
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Out.bRectLight = InLightType == LIGHT_TYPE_RECT;
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Out.RectLightData.BarnCosAngle = DeferredLightUniforms.RectLightBarnCosAngle;
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Out.RectLightData.BarnLength = DeferredLightUniforms.RectLightBarnLength;
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Out.RectLightData.AtlasData.AtlasMaxLevel = DeferredLightUniforms.RectLightAtlasMaxLevel;
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Out.RectLightData.AtlasData.AtlasUVOffset = DeferredLightUniforms.RectLightAtlasUVOffset;
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Out.RectLightData.AtlasData.AtlasUVScale = DeferredLightUniforms.RectLightAtlasUVScale;
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Out.HairTransmittance = InitHairTransmittanceData();
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return Out;
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}
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```
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### DeferredLightPixelMain
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```c++
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void DeferredLightPixelMain(
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#if LIGHT_SOURCE_SHAPE > 0
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float4 InScreenPosition : TEXCOORD0,
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#else
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float2 ScreenUV : TEXCOORD0,
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float3 ScreenVector : TEXCOORD1,
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#endif
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float4 SVPos : SV_POSITION,
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out float4 OutColor : SV_Target0
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#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
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, out float3 OutOpaqueRoughRefractionSceneColor : SV_Target1
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, out float3 OutSubSurfaceSceneColor : SV_Target2
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#endif
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)
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{
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const float2 PixelPos = SVPos.xy;
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OutColor = 0;
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#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
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OutOpaqueRoughRefractionSceneColor = 0;
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OutSubSurfaceSceneColor = 0;
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#endif
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// Convert input data (directional/local light)
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// 计算屏幕UV
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FInputParams InputParams = (FInputParams)0;
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InputParams.PixelPos = SVPos.xy;
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#if LIGHT_SOURCE_SHAPE > 0
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InputParams.ScreenPosition = InScreenPosition;
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InputParams.ScreenUV = InScreenPosition.xy / InScreenPosition.w * View.ScreenPositionScaleBias.xy + View.ScreenPositionScaleBias.wz;
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InputParams.ScreenVector = 0;
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#else
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InputParams.ScreenPosition = 0;
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InputParams.ScreenUV = ScreenUV;
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InputParams.ScreenVector = ScreenVector;
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#endif
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#if STRATA_ENABLED
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FStrataAddressing StrataAddressing = GetStrataPixelDataByteOffset(PixelPos, uint2(View.BufferSizeAndInvSize.xy), Strata.MaxBytesPerPixel);
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FStrataPixelHeader StrataPixelHeader = UnpackStrataHeaderIn(Strata.MaterialTextureArray, StrataAddressing, Strata.TopLayerTexture);
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BRANCH
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if (StrataPixelHeader.BSDFCount > 0 // This test is also enough to exclude sky pixels
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#if USE_LIGHTING_CHANNELS
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//灯光通道逻辑
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&& (GetLightingChannelMask(InputParams.ScreenUV) & DeferredLightUniforms.LightingChannelMask)
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#endif
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)
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{
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//通过SceneDepth获取的CameraVector以及当前像素的世界坐标
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const float SceneDepth = CalcSceneDepth(InputParams.ScreenUV);
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const FDerivedParams DerivedParams = GetDerivedParams(InputParams, SceneDepth);
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//设置获取光源各种信息
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FDeferredLightData LightData = InitDeferredLightFromUniforms(CURRENT_LIGHT_TYPE);
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UpdateLightDataColor(LightData, InputParams, DerivedParams);//根据当前世界坐标计算LightData.Color *= 大气&云&阴影的衰减值 * IES灯亮度（非IES灯数值为1）
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float3 V =-DerivedParams.CameraVector;
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float3 L = LightData.Direction; // Already normalized
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float3 ToLight = L;
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float LightMask = 1;
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if (LightData.bRadialLight)
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{
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LightMask = GetLocalLightAttenuation(DerivedParams.TranslatedWorldPosition, LightData, ToLight, L);
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}
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if (LightMask > 0)
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{
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FShadowTerms ShadowTerms = { StrataGetAO(StrataPixelHeader), 1.0, 1.0, InitHairTransmittanceData() };
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float4 LightAttenuation = GetLightAttenuationFromShadow(InputParams, SceneDepth);
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float Dither = InterleavedGradientNoise(InputParams.PixelPos, View.StateFrameIndexMod8);
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const uint FakeShadingModelID = 0;
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const float FakeContactShadowOpacity = 1.0f;
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float4 PrecomputedShadowFactors = StrataReadPrecomputedShadowFactors(StrataPixelHeader, PixelPos, SceneTexturesStruct.GBufferETexture);
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GetShadowTerms(SceneDepth, PrecomputedShadowFactors, FakeShadingModelID, FakeContactShadowOpacity,
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LightData, DerivedParams.TranslatedWorldPosition, L, LightAttenuation, Dither, ShadowTerms);
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FStrataDeferredLighting StrataLighting = StrataDeferredLighting(
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LightData,
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V,
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L,
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ToLight,
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LightMask,
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ShadowTerms,
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Strata.MaterialTextureArray,
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StrataAddressing,
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StrataPixelHeader);
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OutColor += StrataLighting.SceneColor;
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#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
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OutOpaqueRoughRefractionSceneColor += StrataLighting.OpaqueRoughRefractionSceneColor;
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OutSubSurfaceSceneColor += StrataLighting.SubSurfaceSceneColor;
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#endif
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}
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}
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#else // STRATA_ENABLED
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//取得屏幕空间数据（FGbufferData、AO）
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FScreenSpaceData ScreenSpaceData = GetScreenSpaceData(InputParams.ScreenUV);
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// Only light pixels marked as using deferred shading
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BRANCH if (ScreenSpaceData.GBuffer.ShadingModelID > 0
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#if USE_LIGHTING_CHANNELS
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&& (GetLightingChannelMask(InputParams.ScreenUV) & DeferredLightUniforms.LightingChannelMask)
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#endif
|
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)
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{
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//通过SceneDepth获取的CameraVector以及当前像素的世界坐标
|
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const float SceneDepth = CalcSceneDepth(InputParams.ScreenUV);
|
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const FDerivedParams DerivedParams = GetDerivedParams(InputParams, SceneDepth);
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//设置获取光源各种信息
|
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FDeferredLightData LightData = InitDeferredLightFromUniforms(CURRENT_LIGHT_TYPE);
|
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UpdateLightDataColor(LightData, InputParams, DerivedParams);//根据当前世界坐标计算LightData.Color *= 大气&云&阴影的衰减值 * IES灯亮度（非IES灯数值为1）
|
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#if USE_HAIR_COMPLEX_TRANSMITTANCE
|
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//针对ShadingModel Hair（同时需要CustomData.a > 0)计算头发散射结果
|
||
if (ScreenSpaceData.GBuffer.ShadingModelID == SHADINGMODELID_HAIR && ShouldUseHairComplexTransmittance(ScreenSpaceData.GBuffer))
|
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{
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LightData.HairTransmittance = EvaluateDualScattering(ScreenSpaceData.GBuffer, DerivedParams.CameraVector, -DeferredLightUniforms.Direction);
|
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}
|
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#endif
|
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//计算当前像素的抖动值
|
||
float Dither = InterleavedGradientNoise(InputParams.PixelPos, View.StateFrameIndexMod8);
|
||
|
||
float SurfaceShadow = 1.0f;
|
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|
||
float4 LightAttenuation = GetLightAttenuationFromShadow(InputParams, SceneDepth);//根绝是否开启VSM 分别从VirtualShadowMap 或者 LightAttenuationTexture（上一阶段渲染的ShadowProjction） 获取灯光衰减值。
|
||
float4 Radiance = GetDynamicLighting(DerivedParams.TranslatedWorldPosition, DerivedParams.CameraVector, ScreenSpaceData.GBuffer, ScreenSpaceData.AmbientOcclusion, ScreenSpaceData.GBuffer.ShadingModelID, LightData, LightAttenuation, Dither, uint2(InputParams.PixelPos), SurfaceShadow);
|
||
|
||
OutColor += Radiance;
|
||
}
|
||
|
||
#endif // STRATA_ENABLED
|
||
|
||
// RGB:SceneColor Specular and Diffuse
|
||
// A:Non Specular SceneColor Luminance
|
||
// So we need PreExposure for both color and alpha
|
||
OutColor.rgba *= GetExposure();
|
||
#if STRATA_OPAQUE_ROUGH_REFRACTION_ENABLED
|
||
// Idem
|
||
OutOpaqueRoughRefractionSceneColor *= GetExposure();
|
||
OutSubSurfaceSceneColor *= GetExposure();
|
||
#endif
|
||
}
|
||
#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(
|
||
float3 TranslatedWorldPosition, float3 CameraVector, FGBufferData GBuffer, float AmbientOcclusion, uint ShadingModelID,
|
||
FDeferredLightData LightData, float4 LightAttenuation, float Dither, uint2 SVPos,
|
||
inout float SurfaceShadow)
|
||
{
|
||
FLightAccumulator LightAccumulator = AccumulateDynamicLighting(TranslatedWorldPosition, CameraVector, GBuffer, AmbientOcclusion, ShadingModelID, LightData, LightAttenuation, Dither, SVPos, SurfaceShadow);
|
||
return LightAccumulator_GetResultSplit(LightAccumulator);
|
||
}
|
||
```
|
||
|
||
LightAccumulator_GetResultSplit()：针对Subsurface，`RetDiffuse.a = In.ScatterableLightLuma;` 或者 `RetDiffuse.a = Luminance(In.ScatterableLight);`
|
||
```c++
|
||
FDeferredLightingSplit LightAccumulator_GetResultSplit(FLightAccumulator In)
|
||
{
|
||
float4 RetDiffuse;
|
||
float4 RetSpecular;
|
||
|
||
if (VISUALIZE_LIGHT_CULLING == 1)
|
||
{
|
||
// a soft gradient from dark red to bright white, can be changed to be different
|
||
RetDiffuse = 0.1f * float4(1.0f, 0.25f, 0.075f, 0) * In.EstimatedCost;
|
||
RetSpecular = 0.1f * float4(1.0f, 0.25f, 0.075f, 0) * In.EstimatedCost;
|
||
}
|
||
else
|
||
{
|
||
RetDiffuse = float4(In.TotalLightDiffuse, 0);
|
||
RetSpecular = float4(In.TotalLightSpecular, 0);
|
||
|
||
//针对Subsurface会额外对RetDiffuse的Alpha设置数值 ScatterableLight的亮度数值
|
||
if (SUBSURFACE_CHANNEL_MODE == 1 )
|
||
{
|
||
if (View.bCheckerboardSubsurfaceProfileRendering == 0)
|
||
{
|
||
// RGB accumulated RGB HDR color, A: specular luminance for screenspace subsurface scattering
|
||
RetDiffuse.a = In.ScatterableLightLuma;
|
||
}
|
||
}
|
||
else if (SUBSURFACE_CHANNEL_MODE == 2)
|
||
{
|
||
// RGB accumulated RGB HDR color, A: view independent (diffuse) luminance for screenspace subsurface scattering
|
||
// 3 add, 1 mul, 2 mad, can be optimized to use 2 less temporary during accumulation and remove the 3 add
|
||
RetDiffuse.a = Luminance(In.ScatterableLight);
|
||
// todo, need second MRT for SUBSURFACE_CHANNEL_MODE==2
|
||
}
|
||
}
|
||
|
||
FDeferredLightingSplit Ret;
|
||
Ret.DiffuseLighting = RetDiffuse;
|
||
Ret.SpecularLighting = RetSpecular;
|
||
|
||
return Ret;
|
||
}
|
||
```
|
||
#### AccumulateDynamicLighting
|
||
```c++
|
||
FLightAccumulator AccumulateDynamicLighting(
|
||
float3 TranslatedWorldPosition, half3 CameraVector, FGBufferData GBuffer, half AmbientOcclusion, uint ShadingModelID,
|
||
FDeferredLightData LightData, half4 LightAttenuation, float Dither, uint2 SVPos,
|
||
inout float SurfaceShadow)
|
||
{
|
||
FLightAccumulator LightAccumulator = (FLightAccumulator)0;
|
||
|
||
half3 V = -CameraVector;
|
||
half3 N = GBuffer.WorldNormal;
|
||
//针对开启CLEAR_COAT_BOTTOM_NORMAL的清漆ShadingModel进行Normal处理
|
||
BRANCH if( GBuffer.ShadingModelID == SHADINGMODELID_CLEAR_COAT && CLEAR_COAT_BOTTOM_NORMAL)
|
||
{
|
||
const float2 oct1 = ((float2(GBuffer.CustomData.a, GBuffer.CustomData.z) * 4) - (512.0/255.0)) + UnitVectorToOctahedron(GBuffer.WorldNormal);
|
||
N = OctahedronToUnitVector(oct1);
|
||
}
|
||
|
||
float3 L = LightData.Direction; // Already normalized
|
||
float3 ToLight = L;
|
||
float3 MaskedLightColor = LightData.Color;//灯光颜色
|
||
float LightMask = 1;
|
||
// 获取辐射光源的衰减值，衰减方法根据LightData.bInverseSquared，会分别使用新版衰减方法InverseSquared 或者 旧方法。如果是SpotLight与RectLight就乘以SpotLight、RectLight对应的形状衰减数值。
|
||
if (LightData.bRadialLight)
|
||
{
|
||
LightMask = GetLocalLightAttenuation( TranslatedWorldPosition, LightData, ToLight, L );
|
||
MaskedLightColor *= LightMask;
|
||
}
|
||
|
||
LightAccumulator.EstimatedCost += 0.3f; // running the PixelShader at all has a cost
|
||
|
||
BRANCH
|
||
if( LightMask > 0 )//如果不是完全死黑就计算阴影部分逻辑
|
||
{
|
||
FShadowTerms Shadow;
|
||
Shadow.SurfaceShadow = AmbientOcclusion;//GBuffer中的AO
|
||
Shadow.TransmissionShadow = 1;
|
||
Shadow.TransmissionThickness = 1;
|
||
Shadow.HairTransmittance.OpaqueVisibility = 1;
|
||
const float ContactShadowOpacity = GBuffer.CustomData.a;//TODO:修正ToonStandard对应的逻辑
|
||
//
|
||
GetShadowTerms(GBuffer.Depth, GBuffer.PrecomputedShadowFactors, GBuffer.ShadingModelID, ContactShadowOpacity,
|
||
LightData, TranslatedWorldPosition, L, LightAttenuation, Dither, Shadow);
|
||
SurfaceShadow = Shadow.SurfaceShadow;
|
||
|
||
LightAccumulator.EstimatedCost += 0.3f; // add the cost of getting the shadow terms
|
||
|
||
#if SHADING_PATH_MOBILE
|
||
const bool bNeedsSeparateSubsurfaceLightAccumulation = UseSubsurfaceProfile(GBuffer.ShadingModelID);
|
||
|
||
FDirectLighting Lighting = (FDirectLighting)0;
|
||
|
||
half NoL = max(0, dot(GBuffer.WorldNormal, L));
|
||
#if TRANSLUCENCY_NON_DIRECTIONAL
|
||
NoL = 1.0f;
|
||
#endif
|
||
Lighting = EvaluateBxDF(GBuffer, N, V, L, NoL, Shadow);
|
||
|
||
Lighting.Specular *= LightData.SpecularScale;
|
||
|
||
LightAccumulator_AddSplit( LightAccumulator, Lighting.Diffuse, Lighting.Specular, Lighting.Diffuse, MaskedLightColor * Shadow.SurfaceShadow, bNeedsSeparateSubsurfaceLightAccumulation );
|
||
LightAccumulator_AddSplit( LightAccumulator, Lighting.Transmission, 0.0f, Lighting.Transmission, MaskedLightColor * Shadow.TransmissionShadow, bNeedsSeparateSubsurfaceLightAccumulation );
|
||
#else // SHADING_PATH_MOBILE
|
||
BRANCH
|
||
if( Shadow.SurfaceShadow + Shadow.TransmissionShadow > 0 )
|
||
{
|
||
const bool bNeedsSeparateSubsurfaceLightAccumulation = UseSubsurfaceProfile(GBuffer.ShadingModelID);//判断是否需要SubsurfaceProfile计算
|
||
|
||
#if NON_DIRECTIONAL_DIRECT_LIGHTING
|
||
float Lighting;
|
||
|
||
if( LightData.bRectLight )
|
||
{
|
||
FRect Rect = GetRect( ToLight, LightData );
|
||
|
||
Lighting = IntegrateLight( Rect );
|
||
}
|
||
else
|
||
{
|
||
FCapsuleLight Capsule = GetCapsule( ToLight, LightData );
|
||
|
||
Lighting = IntegrateLight( Capsule, LightData.bInverseSquared );
|
||
}
|
||
|
||
float3 LightingDiffuse = Diffuse_Lambert( GBuffer.DiffuseColor ) * Lighting;
|
||
LightAccumulator_AddSplit(LightAccumulator, LightingDiffuse, 0.0f, 0, MaskedLightColor * Shadow.SurfaceShadow, bNeedsSeparateSubsurfaceLightAccumulation);
|
||
#else
|
||
FDirectLighting Lighting;
|
||
|
||
if (LightData.bRectLight)
|
||
{
|
||
FRect Rect = GetRect( ToLight, LightData );
|
||
const FRectTexture SourceTexture = ConvertToRectTexture(LightData);
|
||
|
||
#if REFERENCE_QUALITY
|
||
Lighting = IntegrateBxDF( GBuffer, N, V, Rect, Shadow, SourceTexture, SVPos );
|
||
#else
|
||
Lighting = IntegrateBxDF( GBuffer, N, V, Rect, Shadow, SourceTexture);
|
||
#endif
|
||
}
|
||
else
|
||
{
|
||
FCapsuleLight Capsule = GetCapsule( ToLight, LightData );
|
||
|
||
#if REFERENCE_QUALITY
|
||
Lighting = IntegrateBxDF( GBuffer, N, V, Capsule, Shadow, SVPos );
|
||
#else
|
||
Lighting = IntegrateBxDF( GBuffer, N, V, Capsule, Shadow, LightData.bInverseSquared );
|
||
#endif
|
||
}
|
||
|
||
Lighting.Specular *= LightData.SpecularScale;
|
||
|
||
LightAccumulator_AddSplit( LightAccumulator, Lighting.Diffuse, Lighting.Specular, Lighting.Diffuse, MaskedLightColor * Shadow.SurfaceShadow, bNeedsSeparateSubsurfaceLightAccumulation );
|
||
LightAccumulator_AddSplit( LightAccumulator, Lighting.Transmission, 0.0f, Lighting.Transmission, MaskedLightColor * Shadow.TransmissionShadow, bNeedsSeparateSubsurfaceLightAccumulation );
|
||
|
||
LightAccumulator.EstimatedCost += 0.4f; // add the cost of the lighting computations (should sum up to 1 form one light)
|
||
#endif
|
||
}
|
||
#endif // SHADING_PATH_MOBILE
|
||
}
|
||
return LightAccumulator;
|
||
}
|
||
```
|
||
|
||
光源新衰减公式，相关计算位于`GetLocalLightAttenuation()`：
|
||
$$Falloff = \frac{saturate(1-(distance/lightRadius)^4)^2}{distance^2 + 1}$$
|
||
|
||
光源旧衰减公式，相关函数位于DynamicLightingCommon.ush中的`RadialAttenuation()`
|
||
$$Falloff = (1 - saturate(length(WorldLightVector)))^ {FalloffExponent}$$
|
||
##### GetShadowTerms()
|
||
```c++
|
||
void GetShadowTerms(float SceneDepth, half4 PrecomputedShadowFactors, uint ShadingModelID, float ContactShadowOpacity, FDeferredLightData LightData, float3 TranslatedWorldPosition, half3 L, half4 LightAttenuation, float Dither, inout FShadowTerms Shadow)
|
||
{
|
||
float ContactShadowLength = 0.0f;
|
||
const float ContactShadowLengthScreenScale = GetTanHalfFieldOfView().y * SceneDepth;
|
||
|
||
BRANCH
|
||
if (LightData.ShadowedBits)
|
||
{
|
||
// 重新映射ShadowProjection结果
|
||
// Remapping the light attenuation buffer (see ShadowRendering.cpp)
|
||
|
||
// LightAttenuation: Light function + per-object shadows in z, per-object SSS shadowing in w,
|
||
// Whole scene directional light shadows in x, whole scene directional light SSS shadows in y
|
||
// Get static shadowing from the appropriate GBuffer channel
|
||
#if ALLOW_STATIC_LIGHTING
|
||
half UsesStaticShadowMap = dot(LightData.ShadowMapChannelMask, half4(1, 1, 1, 1));
|
||
half StaticShadowing = lerp(1, dot(PrecomputedShadowFactors, LightData.ShadowMapChannelMask), UsesStaticShadowMap);
|
||
#else
|
||
half StaticShadowing = 1.0f;
|
||
#endif
|
||
|
||
if (LightData.bRadialLight || SHADING_PATH_MOBILE)//RadialLight或者是移动端使用以下逻辑。bRadialLight一般是 PointLight or SpotLight。径向衰减（radial attenuation）：指光照强度随距离光源的远近而衰减的特性（通常遵循平方反比定律）。
|
||
{
|
||
// Remapping the light attenuation buffer (see ShadowRendering.cpp)
|
||
|
||
Shadow.SurfaceShadow = LightAttenuation.z * StaticShadowing;//RadialLight灯光的阴影项计算不受AO影响，赋值Light function + per-object的ShadowProjection
|
||
// SSS uses a separate shadowing term that allows light to penetrate the surface
|
||
//@todo - how to do static shadowing of SSS correctly?
|
||
Shadow.TransmissionShadow = LightAttenuation.w * StaticShadowing;//per-object SSS shadowing
|
||
|
||
Shadow.TransmissionThickness = LightAttenuation.w;//per-object SSS shadowing
|
||
}
|
||
else
|
||
{
|
||
// Remapping the light attenuation buffer (see ShadowRendering.cpp)
|
||
// Also fix up the fade between dynamic and static shadows
|
||
// to work with plane splits rather than spheres.
|
||
|
||
float DynamicShadowFraction = DistanceFromCameraFade(SceneDepth, LightData);
|
||
// For a directional light, fade between static shadowing and the whole scene dynamic shadowing based on distance + per object shadows
|
||
Shadow.SurfaceShadow = lerp(LightAttenuation.x, StaticShadowing, DynamicShadowFraction);//根据计算出动态阴影的衰减值来插值ShadowProject与静态阴影。x:方向光阴影
|
||
// Fade between SSS dynamic shadowing and static shadowing based on distance
|
||
Shadow.TransmissionShadow = min(lerp(LightAttenuation.y, StaticShadowing, DynamicShadowFraction), LightAttenuation.w);// w:per-object SSS shadowing
|
||
|
||
Shadow.SurfaceShadow *= LightAttenuation.z;//Light function + per-object shadows in z
|
||
Shadow.TransmissionShadow *= LightAttenuation.z;
|
||
|
||
// Need this min or backscattering will leak when in shadow which cast by non perobject shadow(Only for directional light)
|
||
Shadow.TransmissionThickness = min(LightAttenuation.y, LightAttenuation.w);
|
||
}
|
||
|
||
FLATTEN
|
||
if (LightData.ShadowedBits > 1 && LightData.ContactShadowLength > 0)
|
||
{
|
||
ContactShadowLength = LightData.ContactShadowLength * (LightData.ContactShadowLengthInWS ? 1.0f : ContactShadowLengthScreenScale);
|
||
}
|
||
}
|
||
|
||
#if SUPPORT_CONTACT_SHADOWS //接触阴影相关逻辑
|
||
|
||
#if STRATA_ENABLED == 0
|
||
if (LightData.ShadowedBits < 2 && (ShadingModelID == SHADINGMODELID_HAIR))
|
||
{
|
||
ContactShadowLength = 0.2 * ContactShadowLengthScreenScale;
|
||
}
|
||
// World space distance to cover eyelids and eyelashes but not beyond
|
||
if (ShadingModelID == SHADINGMODELID_EYE)
|
||
{
|
||
ContactShadowLength = 0.5;
|
||
|
||
}
|
||
#endif
|
||
|
||
#if MATERIAL_CONTACT_SHADOWS
|
||
ContactShadowLength = 0.2 * ContactShadowLengthScreenScale;
|
||
#endif
|
||
|
||
BRANCH
|
||
if (ContactShadowLength > 0.0)
|
||
{
|
||
float StepOffset = Dither - 0.5;
|
||
bool bHitCastContactShadow = false;
|
||
bool bHairNoShadowLight = ShadingModelID == SHADINGMODELID_HAIR && !LightData.ShadowedBits;
|
||
float HitDistance = ShadowRayCast( TranslatedWorldPosition, L, ContactShadowLength, 8, StepOffset, bHairNoShadowLight, bHitCastContactShadow );//通过RayMarching来计算是否HitContactShadow以及HitDistance。
|
||
|
||
if ( HitDistance > 0.0 )
|
||
{
|
||
float ContactShadowOcclusion = bHitCastContactShadow ? LightData.ContactShadowCastingIntensity : LightData.ContactShadowNonCastingIntensity;
|
||
|
||
#if STRATA_ENABLED == 0
|
||
// Exponential attenuation is not applied on hair/eye/SSS-profile here, as the hit distance (shading-point to blocker) is different from the estimated
|
||
// thickness (closest-point-from-light to shading-point), and this creates light leaks. Instead we consider first hit as a blocker (old behavior)
|
||
BRANCH
|
||
if (ContactShadowOcclusion > 0.0 &&
|
||
IsSubsurfaceModel(ShadingModelID) &&
|
||
ShadingModelID != SHADINGMODELID_HAIR &&
|
||
ShadingModelID != SHADINGMODELID_EYE &&
|
||
ShadingModelID != SHADINGMODELID_SUBSURFACE_PROFILE)
|
||
{
|
||
// Reduce the intensity of the shadow similar to the subsurface approximation used by the shadow maps path
|
||
// Note that this is imperfect as we don't really have the "nearest occluder to the light", but this should at least
|
||
// ensure that we don't darken-out the subsurface term with the contact shadows
|
||
float Density = SubsurfaceDensityFromOpacity(ContactShadowOpacity);
|
||
ContactShadowOcclusion *= 1.0 - saturate( exp( -Density * HitDistance ) );
|
||
}
|
||
#endif
|
||
|
||
float ContactShadow = 1.0 - ContactShadowOcclusion;
|
||
//根据是否命中赋予对应的ContactShadow亮度数值，之后乘以Shadow.SurfaceShadow与Shadow.TransmissionShadow。
|
||
Shadow.SurfaceShadow *= ContactShadow;
|
||
Shadow.TransmissionShadow *= ContactShadow;
|
||
}
|
||
|
||
}
|
||
#endif
|
||
|
||
Shadow.HairTransmittance = LightData.HairTransmittance;
|
||
Shadow.HairTransmittance.OpaqueVisibility = Shadow.SurfaceShadow;
|
||
}
|
||
``` |