From beb8ab2c0c5fd3e7133bae923433bae76681816e Mon Sep 17 00:00:00 2001
From: BlueRose <378100977@qq.com>
Date: Thu, 15 Aug 2024 17:28:55 +0800
Subject: [PATCH] vault backup: 2024-08-15 17:28:55

---
 .../Rendering/RenderingPipeline/GPUScene.md   | 44 ++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/03-UnrealEngine/Rendering/RenderingPipeline/GPUScene.md b/03-UnrealEngine/Rendering/RenderingPipeline/GPUScene.md
index c9eef69..45c94c9 100644
--- a/03-UnrealEngine/Rendering/RenderingPipeline/GPUScene.md
+++ b/03-UnrealEngine/Rendering/RenderingPipeline/GPUScene.md
@@ -32,4 +32,46 @@ for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)
     
     Scene->GPUScene.DebugRender(GraphBuilder, *Scene, GetSceneUniforms(), View);  
 }
-```
\ No newline at end of file
+```
+
+## GPUScene数据更新
+```c++
+// 函数调用关系
+void FDeferredShadingSceneRenderer::Render(FRDGBuilder& GraphBuilder)
+{
+	void FGPUScene::Update(FRDGBuilder& GraphBuilder, FScene& Scene, FRDGExternalAccessQueue& ExternalAccessQueue)
+	{		
+		void FGPUScene::UpdateInternal(FRDGBuilder& GraphBuilder, FScene& Scene, FRDGExternalAccessQueue& ExternalAccessQueue)
+	}
+}
+```
+
+### 2.2、更新PrimitiveData
+
+![](https://pic4.zhimg.com/80/v2-8bbde169a322380c8510375091517133_720w.webp)
+
+接下来，对标记为dirty的Primitive进行更新，更新逻辑为找到该Primitive在PrimitiveData Buffer里对应offset位置，对其进行更新。使用模板FUploadDataSourceAdapterScenePrimitives调用UploadGeneral()。
+
+![](https://pic2.zhimg.com/80/v2-8f1c866194961597d4c3a40f24442fb1_720w.webp)
+
+初始化5类Buffer的上传任务TaskContext
+
+后面代码都是在对这个TaskContext进行初始化，然后启动任务，进行数据的上传。
+
+![](https://pic4.zhimg.com/80/v2-57bdcff035f205a83d3ca1a76036b9df_720w.webp)
+
+![](https://pic3.zhimg.com/80/v2-4a22a7aa675804c2598bbd5a60062922_720w.webp)
+
+2.2.1、并行更新Primitive数据，将需要更新的PrimitiveCopy到Upload Buffer里，后续通过ComputeShader进行显存的上传然后更新到目标Buffer里；
+
+![](https://pic3.zhimg.com/80/v2-e0260c108d7428401228dbf7be0408da_720w.webp)
+
+2.2.2、同理InstanceSceneData以及InstancePayloadData数据的处理。
+
+2.2.3、同理InstanceBVHUploader，LightmapUploader。
+
+2.2.4、最后都会调用每个Uploader的***End()方法进行GPU显存的更新***。
+
+总结：数据的上传都一样，将需要更新的数据Copy到对应的UploadBuffer对应的位置里，然后通过对应的ComputeShader进行更新到目标Buffer，在函数FRDGAsyncScatterUploadBuffer::End()里实现，截图：
+
+![](https://pic2.zhimg.com/80/v2-9f1c352cf6fd2900e60280c80e0e3cf1_720w.webp)
\ No newline at end of file