---
title: Untitled
date: 2024-12-08 12:18:54
excerpt: 
tags: 
rating: ⭐
---
# 阴影
## 阴影类型
- **Static Shadow**
- **Cascading Shadow Map**
- **Per Object Shadow**：可移动组件使用的逐物体阴影应用阴影图到物体的包围盒，因此包围盒必须是精确的。对于骨骼网格，这意味着它们应该有一个物理资产。对于粒子系统，任何固定的边界框必须足够大，以容纳所有的粒子。_在网格的Lighting属性组中，Dynamic Inset Shadow可以开启逐物体阴影，对需要高质量高精度的物体非常有用。_
- **Dynamic Shadow**：可移动光源在所有物体上投射出完全动态的阴影(和光)。这种光源的任何数据不会被烘焙到光照图中，它可以自由地在所有东西上投射动态阴影。静态网格、骨架网格、粒子效果等等将完全从可移动光源投射和接收动态阴影。
- **Capsule Shadow**
- **Contact Shadow**
- **Distance Field Shadow**

## 相关类型
- ShadowRendering.h
	**FProjectedShadowInfo**：存储投影阴影先关信息。包含各种变换矩阵、阴影渲染函数以及渲染参数、灯光&场景&图元信息。
- SceneRendering.h
	FVisibleLightInfo：可见光源信息, 主要是阴影相关的信息.
	FVisibleLightViewInfo：

## DynamicShadows
### InitDynamicShadows() => CreateDynamicShadows() 
InitViews() => FSceneRenderer::InitDynamicShadows()
PS. UE5.3中相关逻辑移动到***CreateDynamicShadows()*** 中了。InitDynamicShadows() => BeginInitDynamicShadows() => BeginGatherShadowPrimitives() => CreateDynamicShadows()

计算各种灯光类型，之后调用：
- CreateWholeSceneProjectedShadow()
- AddViewDependentWholeSceneShadowsForView()
- SetupInteractionShadows()
### CreateWholeSceneProjectedShadow



# 阴影偏移
可以考虑的Buffer有
- ShadowDepths
- CustomDepth

# 相关Paas
1. ShadowDepths
2. Lights 
	1. DirectLighting
		1. UnbatchedLights
			1. ShadowProjectionOnOpaque
# ShadowDepths
- FSceneRenderer::RenderShadowDepthMaps()：位于CustomDepth之前。
	- RenderVirtualShadowMaps()
	- RenderShadowDepthMapAtlases()
	- SortedShadowsForShadowDepthPass.ShadowMapCubemaps循环
		- 
# Lights
### Shader
ShadowProjectionPixelShader.usf
- TShadowProjectionPS：
- TDirectionalPercentageCloserShadowProjectionPS：方向光投影
- TSpotPercentageCloserShadowProjectionPS：SpotLight
- FOnePassPointShadowProjectionPS(Moible?)

### 相关函数
- FDeferredShadingSceneRenderer::RenderLights()
	- FDeferredShadingSceneRenderer::RenderDeferredShadowProjections()
		- FSceneRenderer::RenderShadowProjections()
			- FProjectedShadowInfo::SetupFrustumForProjection()：构建阴影投影4棱椎平面信息。
			- FProjectedShadowInfo::SetupProjectionStencilMask()：

# 其他
顺序：
RenderCustomDepthPass

FSceneRenderer::CreateDynamicShadows
=>
FSceneRenderer::CreatePerObjectProjectedShadow

```c++
if (!IsForwardShadingEnabled(ShaderPlatform))  
{  
    // Dynamic shadows are synced later when using the deferred path to make more headroom for tasks.  
    FinishInitDynamicShadows(GraphBuilder, InitViewTaskDatas.DynamicShadows, InstanceCullingManager, ExternalAccessQueue);  
}
```

```c++
if (RendererOutput == ERendererOutput::DepthPrepassOnly)
	{
		RenderOcclusionLambda();

		if (bUpdateNaniteStreaming)
		{
			Nanite::GStreamingManager.SubmitFrameStreamingRequests(GraphBuilder);
		}

		CopySceneCaptureComponentToTarget(GraphBuilder, SceneTextures, ViewFamilyTexture, ViewFamily, Views);
	}
	else
	{
		GVRSImageManager.PrepareImageBasedVRS(GraphBuilder, ViewFamily, SceneTextures);

		if (!IsForwardShadingEnabled(ShaderPlatform))
		{
			// Dynamic shadows are synced later when using the deferred path to make more headroom for tasks.
			FinishInitDynamicShadows(GraphBuilder, InitViewTaskDatas.DynamicShadows, InstanceCullingManager, ExternalAccessQueue);
		}

		// Update groom only visible in shadow
		if (IsHairStrandsEnabled(EHairStrandsShaderType::All, Scene->GetShaderPlatform()) && RendererOutput == ERendererOutput::FinalSceneColor)
		{
			UpdateHairStrandsBookmarkParameters(Scene, Views, HairStrandsBookmarkParameters);

			// Interpolation for cards/meshes only visible in shadow needs to happen after the shadow jobs are completed
			const bool bRunHairStrands = HairStrandsBookmarkParameters.HasInstances() && (Views.Num() > 0);
			if (bRunHairStrands)
			{
				RunHairStrandsBookmark(GraphBuilder, EHairStrandsBookmark::ProcessCardsAndMeshesInterpolation_ShadowView, HairStrandsBookmarkParameters);
			}
		}
	
		// NOTE: The ordering of the lights is used to select sub-sets for different purposes, e.g., those that support clustered deferred.
		FSortedLightSetSceneInfo& SortedLightSet = *GraphBuilder.AllocObject<FSortedLightSetSceneInfo>();
		{
			RDG_CSV_STAT_EXCLUSIVE_SCOPE(GraphBuilder, SortLights);
			RDG_GPU_STAT_SCOPE(GraphBuilder, SortLights);
			ComputeLightGridOutput = GatherLightsAndComputeLightGrid(GraphBuilder, bComputeLightGrid, SortedLightSet);
		}
```