216 lines
8.2 KiB
Markdown
216 lines
8.2 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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