vault backup: 2025-06-10 18:47:39

03-UnrealEngine/Rendering/RenderFeature/ShaderWorldPlugin/ShaderWorld.md

@@ -47,8 +47,7 @@ AShaderWorldActor::ProcessSegmentedComputation() <- AShaderWorldActor::TerrainAn
 
 
 # 其他Bug
-CacheMatDyn？
-MatDyn？
+
 
 ## SetTextureParameterValue相关逻辑排查
 - AShaderWorldActor中的SetTextureParameterValue
@@ -56,21 +55,62 @@ MatDyn？
 	- ~~AssignHeightMapToDynamicMaterial~~
 	- UpdateStaticDataFor
 	- ComputeHeight_Segmented_MapForClipMap：似乎会设置
-	- UpdateCollisionMeshData
+	- ~~UpdateCollisionMeshData~~
 	- [x] [[#InitializeReadBackDependencies]]
 	- [x] InitiateMaterials
 
+### UpdateStaticDataFor
 
-### UpdateCollisionMeshData
- Tick() -> CollisionManagement() -> CollisionGPU() -> UpdateCollisionMeshData()
 
 ### ComputeHeight_Segmented_MapForClipMap
+AShaderWorldActor::Tick() -> AShaderWorldActor::TerrainAndSpawnablesManagement() -> AShaderWorldActor::ProcessSegmentedComputation() -> ComputeHeight_Segmented_MapForClipMap
 
+ 
 
+### UpdateCollisionMeshData
+ - 作用：
+	 1. 判断DynCollisionMat是否有效，无效就使用`Generator`（高度数据生成材质）来创建。
+	 2. 设置材质参数NoMargin、TexelPerSide、PatchFullSize、MeshScale。
+	 3. 设置随机种子相关的材质参数。
+	 4. 设置材质参数PatchLocation。
+	 5. 生成碰撞数据到`CollisionRT`。
+	 6. 笔刷功能逻辑：ApplyBrushStackToHeightMap()。
+	 7. ExportPhysicalMaterialID逻辑。
+	 8. GPU碰撞数据回读：ShaderWorld::AsyncReadPixelsFromRT()。
+		 1. ShaderWorld::GSWReadbackManager.AddPendingReadBack()，将回读Task增加`TArray<FReadBackTask> PendingReads;`。
+		 2. 之后会在USWorldSubsystem::Tick()中调用ShaderWorld::GSWReadbackManager.TickReadBack()，不断检查是否可回读，并进行最终回读。
+ - 调用顺序：Tick() -> CollisionManagement() -> CollisionGPU() -> UpdateCollisionMeshData()
+
+```c++
+namespace ShaderWorld
+{
+	FORCEINLINE void AsyncReadPixelsFromRT(UShaderWorldRT2D* InRT, TSharedPtr<FSWColorRead, ESPMode::ThreadSafe> Destination, TSharedPtr < FThreadSafeBool, ESPMode::ThreadSafe> Completion)
+	{
+
+		ENQUEUE_RENDER_COMMAND(ReadGeoClipMapRTCmd)(
+			[InRT, HeightData = Destination, Completion = Completion](FRHICommandListImmediate& RHICmdList)
+			{
+				check(IsInRenderingThread());
+
+				if (HeightData.IsValid() && InRT->GetResource())
+				{
+					FRDGBuilder GraphBuilder(RHICmdList);
+					TSharedPtr<FRHIGPUTextureReadback> ReadBackStaging = MakeShared<FRHIGPUTextureReadback>(TEXT("SWGPUTextureReadback"));
+					FRDGTextureRef RDGSourceTexture = RegisterExternalTexture(GraphBuilder, InRT->GetResource()->TextureRHI, TEXT("SWSourceTextureToReadbackTexture"));
+					AddEnqueueCopyPass(GraphBuilder, ReadBackStaging.Get(), RDGSourceTexture);
+					GraphBuilder.Execute();
+
+					ShaderWorld::GSWReadbackManager.AddPendingReadBack(RHICmdList, GPixelFormats[RDGSourceTexture->Desc.Format].BlockBytes, RDGSourceTexture->Desc.Extent.X, RDGSourceTexture->Desc.Extent.Y, ReadBackStaging, const_cast<TSharedPtr<FSWColorRead, ESPMode::ThreadSafe>&>(HeightData), const_cast<TSharedPtr < FThreadSafeBool, ESPMode::ThreadSafe>&>(Completion));
+				}
+
+			});	
+	}
+```
 
 
 ### InitializeReadBackDependencies
-BeginPlay() -> InitiateWorld() -> InitializeReadBackDependencies()
+- 作用：初始化几个GPU数据回读用的RT。
+- 调用顺序：BeginPlay() -> InitiateWorld() -> InitializeReadBackDependencies()
 
 1. 初始化3个RT：ReadRequestLocation、ReadRequestLocationHeightmap、GeneratorDynamicForReadBack。
 2. 会设置`TObjectPtr < UMaterialInstanceDynamic> GeneratorDynamicForReadBack`各种变量