115 lines
5.2 KiB
Markdown
115 lines
5.2 KiB
Markdown
---
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title: Untitled
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date: 2024-12-08 12:18:54
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excerpt:
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tags:
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rating: ⭐
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---
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# 前言
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阴影渲染笔记：[[Shadow]]
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实现功能：
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1. [ ] 控制深度偏移
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2. [ ] CustomDepth制作头发阴影偏移效果哦 https://zhuanlan.zhihu.com/p/689578355
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3. [ ] ContactShadow接触阴影实现衣服细节的DetailShadow
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4. [ ] 半程阴影
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# 半程阴影
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由晨风&Neverwind提出：
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- 【[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
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**阴影Setup阶段**:
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```c++
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if 启用半程阴影:
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{
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额外进行一次CreatePerObjectProjectedShadow()
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{
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处理阴影光照Matrix //猜测：
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//在ProjectedShadowInfo->SetupPerObjectProjection()中调整，FProjectedShadowInfo.TranslatedWorldToView。
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//在LightSceneInfo->Proxy->GetPerObjectProjectedShadowInitializer(Bounds, ShadowInitializer)之后，修改WorldTolight。
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向阴影信息写入IsHalfViewShadowFlag//猜测：在FProjectedShadowInfo中添加判断Flag并且写入。
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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？
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}
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}
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```
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截图代码(半程阴影修改LightDirection逻辑)：
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```c++
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if(PrimitiveSceneinfo->Proxy->IsToonDisableSelfShadow())
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{
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...
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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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const FMatrix& ViewMatrix = View.ShadowViewMatrices.GetViewMatrix()
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FVector LightDirection = Lightsceneinfo->Proxy->GetDirection();
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const FVector CameraDirection = ViewMatrix.GetColumn(2).GetSafeNormal()
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float LightViewBlendFactor = PrimitiveSceneinfo->Proxy->GetToonHalfVienShadowFactor();
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Fvector HalfViewLightDir = (LightDirection + ( 1 - LightViewBlendFactor) + CameraDirection * LightViewBlendFactor).GetSafeNormal();
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FMatrix FinalCombineMatrix = FInverseRotationMatrix(HalfViewLightDir.Rotation())
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ShadowInitializer.WorldToLight = FinalCombineMatrix;
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}
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...
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}
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```
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相关代码位于`FDirectionalLightSceneProxy::GetPerObjectProjectedShadowInitializer()`，在在FSceneRenderer::CreatePerObjectProjectedShadow()被调用。
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```c++
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virtual bool GetPerObjectProjectedShadowInitializer(const FBoxSphereBounds& SubjectBounds,FPerObjectProjectedShadowInitializer& OutInitializer) const override
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{
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OutInitializer.PreShadowTranslation = -SubjectBounds.Origin;
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OutInitializer.WorldToLight = FInverseRotationMatrix(FVector(WorldToLight.M[0][0],WorldToLight.M[1][0],WorldToLight.M[2][0]).GetSafeNormal().Rotation());
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OutInitializer.Scales = FVector2D(1.0f / SubjectBounds.SphereRadius,1.0f / SubjectBounds.SphereRadius);
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OutInitializer.SubjectBounds = FBoxSphereBounds(FVector::ZeroVector,SubjectBounds.BoxExtent,SubjectBounds.SphereRadius);
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OutInitializer.WAxis = FVector4(0,0,0,1);
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OutInitializer.MinLightW = -UE_OLD_HALF_WORLD_MAX;
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// Reduce casting distance on a directional light
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// This is necessary to improve floating point precision in several places, especially when deriving frustum verts from InvReceiverMatrix
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// This takes the object size into account to ensure that large objects get an extended distance
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OutInitializer.MaxDistanceToCastInLightW = FMath::Clamp(SubjectBounds.SphereRadius * CVarPerObjectCastDistanceRadiusScale.GetValueOnRenderThread(), CVarPerObjectCastDistanceMin.GetValueOnRenderThread(), (float)WORLD_MAX);
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return true;
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}
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```
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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。
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**阴影Projection阶段**:
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//此阶段需要屏蔽角色投射到自己的非半程阴影
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//和角色投射到场景中会跟随视角移动的阴影
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```c++
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if(Toon材质,且没有半程阴影Flag的阴影
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&&非Toon材质但有半程阴影Flag的阴影)
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{
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屏蔽此阴影
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}
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```
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PS.很有可能在FProjectedShadowInfo::RenderProjection()阶段进行判断以此保证合成正确的**ScreenShadowMask**。
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# 实现方法
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```c++
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const FMaterialRenderProxy* MaterialRenderProxy = MeshBatch.MaterialRenderProxy;
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bool bEnableToonMeshDrawOutline = MaterialRenderProxy->GetToonOutlineDataAssetRT()->Settings.bEnableToonMeshDrawOutline;
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```
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FProjectedShadowInfo->Scene
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FPrimitiveSceneProxy
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## 深度偏移
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### 方法一
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1. FProjectedShadowInfo添加变量。
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FSceneRenderer::RenderShadowDepthMaps() => RenderShadowDepthMapAtlases() => ProjectedShadowInfo->RenderDepth()
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已放弃，FProjectedShadowInfo无法判断MeshSection。
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### 方法二
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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。
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其优点就是可以用贴图来控制偏移过渡。
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## DirectionOffsetToViewShadow
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1. 在FProjectedShadowInfo添加变量。
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FSceneRenderer::CreateDynamicShadows() => SetupInteractionShadows()，在CreatePerObjectProjectedShadow()添加相关逻辑。
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CreatePerObjectProjectedShadow() => ProjectedPreShadowInfo->SetupPerObjectProjection
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- GetBestShadowTransform()
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- |