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03-UnrealEngine/Rendering/RenderingPipeline/GPUScene.md
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@ -33,3 +33,45 @@ for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)
Scene->GPUScene.DebugRender(GraphBuilder, *Scene, GetSceneUniforms(), View);
}
```
## 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)