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03-UnrealEngine/VirtualProduction/XR拍摄角色没有阴影的解决方案.md
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03-UnrealEngine/VirtualProduction/XR拍摄角色没有阴影的解决方案.md
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---
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title: XR拍摄角色没有阴影的解决方案
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date: 2022-12-05 14:01:39
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excerpt:
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tags: XR
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rating: ⭐
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---
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# 解决方案
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在不修改引擎的情况下，解决思路有：
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1. [[#手动渲染阴影]]
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2. [[#使用Composure进行合成]]
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修改引擎的解决思路有：
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1.
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## 手动渲染阴影
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- 使用ShadowMapMaterialFunction插件渲染渲染阴影并且贴在一个面片上。
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缺点：
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1. 如果快速旋转视角，阴影会有残影效果。**原因：因为这个阴影贴图不是在同一帧渲染出来的关系。**
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## 使用Composure进行合成
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- 使用Composure渲染 Floor（地面模型）、Shadow Layer（地面+角色模型），再通过Shader实现阴影+角色抠像方法。
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- 使用Composure渲染 Floor（地面模型）、Reflection Layer（地面+角色模型），再通过Shader实现反射+角色抠像方法。
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经过测试捕捉反射可以使用绿色面片作为背景，最后使用Chroma进行抠像。
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注意：使用Composure捕捉的结果都是经过ToneMapping，如果把RT再次贴到场景中进行渲染会有2次Tonemaping只是结果“发白”，所以需要在几个Layer中添加Tonemap选项，进行反ToneMapping。
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缺点：
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1. 需要使用多次SceneCapture，会严重降低帧数。即使只捕捉单个物体，渲染消耗也和原始的渲染消耗一样。**建议：把角色与Composure相关的东西，放在一个子关卡中，场景放在一个子关卡中，然后2台机器使用SVN同步完工程之后，启动对应的关卡进行推流。**
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## ~~UPlanarReflectionComponent~~
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核心函数：
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- UPlanarReflectionComponent（主要用于维护Scene的PlanarReflections数组以及数据更新标记bRegisteredReflectionCapturesHasChanged）
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- CreateRenderState_Concurrent()：创建FPlanarReflectionSceneProxy，并且调用Scene->AddPlanarReflection。
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- SendRenderTransform_Concurrent()：调用Scene->UpdatePlanarReflectionTransform。
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- DestroyRenderState_Concurrent()：调用Scene->RemovePlanarReflection(this)，并且删除渲染线程的FPlanarReflectionSceneProxy。
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- PostEditChangeProperty()：更新可见性。
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- FScene
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- UpdatePlanarReflectionContents()：
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- 清理RT并重新初始化RT
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- 计算反射平面与FSceneCaptureViewInfo（主要是View与Projaction矩阵）
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- 构建FSceneViewFamilyContext，可以理解为Capture的画布与相关View变量
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- 调用FSceneRenderer::CreateSceneRenderer()创建渲染器
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- 在渲染线程调用UpdatePlanarReflectionContents_RenderThread()渲染反射结果
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```c++
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// Reflection view late update
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if (SceneRenderer->Views.Num() > 1)
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{ const FMirrorMatrix MirrorMatrix(MirrorPlane);
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for (int32 ViewIndex = 0; ViewIndex < SceneRenderer->Views.Num(); ++ViewIndex)
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{ FViewInfo& ReflectionViewToUpdate = SceneRenderer->Views[ViewIndex];
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const FViewInfo& UpdatedParentView = MainSceneRenderer->Views[ViewIndex];
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ReflectionViewToUpdate.UpdatePlanarReflectionViewMatrix(UpdatedParentView, MirrorMatrix);
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} }
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// Render the scene normally
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{
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RDG_RHI_EVENT_SCOPE(GraphBuilder, RenderScene);
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SceneRenderer->Render(GraphBuilder);
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}
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SceneProxy->RenderTarget = RenderTarget;
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// Update the view rects into the planar reflection proxy.
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for (int32 ViewIndex = 0; ViewIndex < SceneRenderer->Views.Num(); ++ViewIndex)
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{ // Make sure screen percentage has correctly been set on render thread.
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check(SceneRenderer->Views[ViewIndex].ViewRect.Area() > 0);
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SceneProxy->ViewRect[ViewIndex] = SceneRenderer->Views[ViewIndex].ViewRect;
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}
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FRDGTextureRef ReflectionOutputTexture = GraphBuilder.RegisterExternalTexture(CreateRenderTarget(RenderTarget->TextureRHI, TEXT("ReflectionOutputTexture")));
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GraphBuilder.SetTextureAccessFinal(ReflectionOutputTexture, ERHIAccess::SRVGraphics);
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FSceneTextureShaderParameters SceneTextureParameters = CreateSceneTextureShaderParameters(GraphBuilder, &SceneRenderer->GetActiveSceneTextures(), SceneRenderer->FeatureLevel, ESceneTextureSetupMode::SceneDepth);
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const FMinimalSceneTextures& SceneTextures = SceneRenderer->GetActiveSceneTextures();
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for (int32 ViewIndex = 0; ViewIndex < SceneRenderer->Views.Num(); ++ViewIndex)
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{ FViewInfo& View = SceneRenderer->Views[ViewIndex];
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RDG_GPU_MASK_SCOPE(GraphBuilder, View.GPUMask);
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if (MainSceneRenderer->Scene->GetShadingPath() == EShadingPath::Deferred)
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{
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PrefilterPlanarReflection<true>(GraphBuilder, View, SceneTextureParameters, SceneProxy, SceneTextures.Color.Resolve, ReflectionOutputTexture);
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}else
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{
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PrefilterPlanarReflection<false>(GraphBuilder, View, SceneTextureParameters, SceneProxy, SceneTextures.Color.Resolve, ReflectionOutputTexture);
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}
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}
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```
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可行的实现思路：
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1. 将`class FPlanarReflectionRenderTarget* RenderTarget`的结果覆盖到对应的`UTextureRenderTarget2D* `中。
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2. 使用`UTextureRenderTarget2D`数据来对`FPlanarReflectionRenderTarget`进行初始化。
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1. 扩展FPlanarReflectionRenderTarget类，添加新的构造函数，将UTextureRenderTarget2D的数据来扩充内部的RT。进行手动的初始化。
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2. 扩展UPlanarReflectionComponent类，增加UTextureRenderTarget2D选项。
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但因为RenderTarget是Private，所以不修改源码的情况无法实现。
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## 使用SceneCapture2D模拟UPlanarReflectionComponent
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位于PlanarReflectionRendering.cpp的UpdatePlanarReflectionContents_RenderThread()
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计算视锥与反射平面的代码：
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```c++
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const FMatrix ComponentTransform = CaptureComponent->GetComponentTransform().ToMatrixWithScale();
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FPlane MirrorPlane = FPlane(ComponentTransform.TransformPosition(FVector::ZeroVector), ComponentTransform.TransformVector(FVector(0, 0, 1)));
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// Normalize the plane to remove component scaling
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bool bNormalized = MirrorPlane.Normalize();
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if (!bNormalized)
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{
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MirrorPlane = FPlane(FVector(0, 0, 1), 0);
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}
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for (int32 ViewIndex = 0; ViewIndex < MainSceneRenderer.Views.Num() && ViewIndex < GMaxPlanarReflectionViews; ++ViewIndex)
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{
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const FViewInfo& View = MainSceneRenderer.Views[ViewIndex];
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FSceneCaptureViewInfo NewView;
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FVector2D ViewRectMin = FVector2D(View.UnscaledViewRect.Min.X, View.UnscaledViewRect.Min.Y);
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FVector2D ViewRectMax = FVector2D(View.UnscaledViewRect.Max.X, View.UnscaledViewRect.Max.Y);
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ViewRectMin *= FMath::Clamp(CaptureComponent->ScreenPercentage / 100.f, 0.25f, 1.f);
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ViewRectMax *= FMath::Clamp(CaptureComponent->ScreenPercentage / 100.f, 0.25f, 1.f);
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NewView.ViewRect.Min.X = FMath::TruncToInt(ViewRectMin.X);
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NewView.ViewRect.Min.Y = FMath::TruncToInt(ViewRectMin.Y);
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NewView.ViewRect.Max.X = FMath::CeilToInt(ViewRectMax.X);
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NewView.ViewRect.Max.Y = FMath::CeilToInt(ViewRectMax.Y);
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// Create a mirror matrix and premultiply the view transform by it
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const FMirrorMatrix MirrorMatrix(MirrorPlane);
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const FMatrix ViewMatrix(MirrorMatrix * View.ViewMatrices.GetViewMatrix());
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const FVector ViewLocation = ViewMatrix.InverseTransformPosition(FVector::ZeroVector);
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const FMatrix ViewRotationMatrix = ViewMatrix.RemoveTranslation();
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const float HalfFOV = FMath::Atan(1.0f / View.ViewMatrices.GetProjectionMatrix().M[0][0]);
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FMatrix ProjectionMatrix;
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BuildProjectionMatrix(View.UnscaledViewRect.Size(), HalfFOV + FMath::DegreesToRadians(CaptureComponent->ExtraFOV), GNearClippingPlane, ProjectionMatrix);
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NewView.ViewLocation = ViewLocation;
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NewView.ViewRotationMatrix = ViewRotationMatrix;
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NewView.ProjectionMatrix = ProjectionMatrix;
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NewView.StereoPass = View.StereoPass;
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NewView.StereoViewIndex = View.StereoViewIndex;
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SceneCaptureViewInfo.Add(NewView);
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}
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```
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```c++
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void BuildProjectionMatrix(FIntPoint InRenderTargetSize, float InFOV, float InNearClippingPlane, FMatrix& OutProjectionMatrix)
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{
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float const XAxisMultiplier = 1.0f;
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float const YAxisMultiplier = InRenderTargetSize.X / float(InRenderTargetSize.Y);
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if ((int32)ERHIZBuffer::IsInverted)
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{ OutProjectionMatrix = FReversedZPerspectiveMatrix(
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InFOV,
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InFOV,
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XAxisMultiplier,
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YAxisMultiplier,
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InNearClippingPlane,
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InNearClippingPlane
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);
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} else
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{
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OutProjectionMatrix = FPerspectiveMatrix( InFOV, InFOV, XAxisMultiplier, YAxisMultiplier, InNearClippingPlane, InNearClippingPlane ); }}
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```
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其他计算方式：
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```c++
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bool IsInFrustum( AActor* Actor)
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{
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ULocalPlayer* LocalPlayer = GetWorld()->GetFirstLocalPlayerFromController();
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if (LocalPlayer != nullptr && LocalPlayer->ViewportClient != nullptr && LocalPlayer->ViewportClient->Viewport)
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{
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FSceneViewFamilyContext ViewFamily(FSceneViewFamily::ConstructionValues(
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LocalPlayer->ViewportClient->Viewport,
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GetWorld()->Scene,
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LocalPlayer->ViewportClient->EngineShowFlags)
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.SetRealtimeUpdate(true));
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FVector ViewLocation;
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FRotator ViewRotation;
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FSceneView* SceneView = LocalPlayer->CalcSceneView(&ViewFamily, ViewLocation, ViewRotation, LocalPlayer->ViewportClient->Viewport);
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if (SceneView != nullptr)
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{
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return SceneView->ViewFrustum.IntersectSphere(
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Actor->GetActorLocation(), Actor->GetSimpleCollisionRadius());
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}
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}
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return false
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}
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```
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### SceneCapture2D
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位于SceneCaptureRendering.cpp
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# 其他
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## Disguise
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支持的输入方式：
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- sdi传输（采集卡走这个协议）
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- ndi网络传输 （通过网卡网线）
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- smpte2110协议传输（显卡直接插大屏幕）
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## Composure相关问题
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- Transforms
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- Custom Material Pass
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- Post Process Pass Set
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- Tonemap
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- Multi Pass Chroma Keyer
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- Multi Pass Despill
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- Outputs
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- Media Capture：走采集卡推流模式。
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- Image Sequence
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- Player Viewport：可以通过在UE中实现虚拟摄像机，再通过OBS推流。
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- Render Target Asset
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值得注意的是Transforms的Tonemap，这是一个反ToneMapping效果。
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