BlueRoseNote/03-UnrealEngine/卡通渲染相关资料/渲染功能/阴影控制/ToonShadow.md

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title	date	excerpt	tags	rating
Untitled	2024-12-08 12:18:54			⭐

前言

阴影渲染笔记：Shadow

实现功能：

1. 控制深度偏移
2. CustomDepth制作头发阴影偏移效果哦 https://zhuanlan.zhihu.com/p/689578355
3. ContactShadow接触阴影实现衣服细节的DetailShadow
4. 半程阴影

半程阴影

由晨风&Neverwind提出：

• 【[UFSH2024]用虚幻引擎5为《幻塔》定制高品质动画流程风格化渲染管线 | 晨风 Neverwind 完美世界游戏】 【精准空降到 07:27】 https://www.bilibili.com/video/BV1rW2LYvEox/?share_source=copy_web&vd_source=fe8142e8e12816535feaeabd6f6cdc8e&t=447

阴影Setup阶段:

if 启用半程阴影:
{
	额外进行一次CreatePerObjectProjectedShadow()
	{
		处理阴影光照Matrix                //猜测：
											 //在ProjectedShadowInfo->SetupPerObjectProjection()中调整，FProjectedShadowInfo.TranslatedWorldToView。
											 //在LightSceneInfo->Proxy->GetPerObjectProjectedShadowInitializer(Bounds, ShadowInitializer)之后，修改WorldTolight。
		向阴影信息写入IsHalfViewShadowFlag//猜测：在FProjectedShadowInfo中添加判断Flag并且写入。
		用新的光源方向画Atlas             //猜测：给带有对应Flog的DirectionLigh多创建一个对应的Atlas？
	}
}

截图代码(半程阴影修改LightDirection逻辑)：

if(PrimitiveSceneinfo->Proxy->IsToonDisableSelfShadow())
{
...
	for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)
	{
		const FViewInfo& View = Views[ViewIndex];
		const FMatrix& ViewMatrix = View.ShadowViewMatrices.GetViewMatrix()
		FVector LightDirection = Lightsceneinfo->Proxy->GetDirection();
		const FVector CameraDirection = ViewMatrix.GetColumn(2).GetSafeNormal()
		float LightViewBlendFactor = PrimitiveSceneinfo->Proxy->GetToonHalfVienShadowFactor();
		Fvector HalfViewLightDir = (LightDirection + ( 1 - LightViewBlendFactor) + CameraDirection * LightViewBlendFactor).GetSafeNormal();
		FMatrix FinalCombineMatrix = FInverseRotationMatrix(HalfViewLightDir.Rotation())
		ShadowInitializer.WorldToLight = FinalCombineMatrix;
	}
...
 }

相关代码位于FDirectionalLightSceneProxy::GetPerObjectProjectedShadowInitializer()，在在FSceneRenderer::CreatePerObjectProjectedShadow()被调用。

virtual bool GetPerObjectProjectedShadowInitializer(const FBoxSphereBounds& SubjectBounds,FPerObjectProjectedShadowInitializer& OutInitializer) const override
	{
		OutInitializer.PreShadowTranslation = -SubjectBounds.Origin;
		OutInitializer.WorldToLight = FInverseRotationMatrix(FVector(WorldToLight.M[0][0],WorldToLight.M[1][0],WorldToLight.M[2][0]).GetSafeNormal().Rotation());
		OutInitializer.Scales = FVector2D(1.0f / SubjectBounds.SphereRadius,1.0f / SubjectBounds.SphereRadius);
		OutInitializer.SubjectBounds = FBoxSphereBounds(FVector::ZeroVector,SubjectBounds.BoxExtent,SubjectBounds.SphereRadius);
		OutInitializer.WAxis = FVector4(0,0,0,1);
		OutInitializer.MinLightW = -UE_OLD_HALF_WORLD_MAX;
		// Reduce casting distance on a directional light
		// This is necessary to improve floating point precision in several places, especially when deriving frustum verts from InvReceiverMatrix
		// This takes the object size into account to ensure that large objects get an extended distance
		OutInitializer.MaxDistanceToCastInLightW = FMath::Clamp(SubjectBounds.SphereRadius * CVarPerObjectCastDistanceRadiusScale.GetValueOnRenderThread(), CVarPerObjectCastDistanceMin.GetValueOnRenderThread(), (float)WORLD_MAX);

		return true;
	}

PS.很有可能需要创建2个Atlas。Atlas的创建位于FSceneRenderer::AllocateCachedShadowDepthTargets()。数据存储在SortedShadowsForShadowDepthPass.ShadowMapAtlases中。大致由FSceneRenderer::FinishInitDynamicShadows()调用。

阴影Projection阶段: //此阶段需要屏蔽角色投射到自己的非半程阴影 //和角色投射到场景中会跟随视角移动的阴影

if(Toon材质,且没有半程阴影Flag的阴影
&&非Toon材质但有半程阴影Flag的阴影)
{
	屏蔽此阴影
}

PS.很有可能在FProjectedShadowInfo::RenderProjection()阶段进行判断以此保证合成正确的ScreenShadowMask。

实现方法

const FMaterialRenderProxy* MaterialRenderProxy = MeshBatch.MaterialRenderProxy;  
bool bEnableToonMeshDrawOutline = MaterialRenderProxy->GetToonOutlineDataAssetRT()->Settings.bEnableToonMeshDrawOutline;

FProjectedShadowInfo->Scene FPrimitiveSceneProxy

深度偏移

方法一

1. FProjectedShadowInfo添加变量。 FSceneRenderer::RenderShadowDepthMaps() => RenderShadowDepthMapAtlases() => ProjectedShadowInfo->RenderDepth()

已放弃，FProjectedShadowInfo无法判断MeshSection。

方法二

在材质中使用ShadowPassSwitch再对ViewSpace的Z轴方向（使用DirectionalLightVector比较可以只对方向光进行偏移）进行WPO偏移实现。

其优点就是可以用贴图来控制偏移过渡。

DirectionOffsetToViewShadow

1. 在FProjectedShadowInfo添加变量。 FSceneRenderer::CreateDynamicShadows() => SetupInteractionShadows()，在CreatePerObjectProjectedShadow()添加相关逻辑。

CreatePerObjectProjectedShadow() => ProjectedPreShadowInfo->SetupPerObjectProjection

• GetBestShadowTransform()