vault backup: 2025-06-27 18:34:16

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

@@ -16,9 +16,6 @@ rating: ⭐
 		- ShaderWorldActor.h:[[#AShaderWorldActor]]
 		- SWorld.h:[[#ASWorld]]
 
-## FRenderCommandFence
-
-
 # USWorldSubsystem
 主要管理：
 - TArray<USWContextBase*> SW_Contexts 
@@ -168,8 +165,10 @@ void AShaderWorldActor::ReadbacksManagement()
 - bool 
 	- RedbuildCollisionContext
 - Array
-	- CollisionWorkQueue：类型为FCollisionProcessingWork。
+	- CollisionReadToProcess：
-	- CollisionReadToProcess
+	- CollisionWorkQueue：类型为FCollisionProcessingWork，碰撞处理任务队列，将回读的
+- FCollisionMeshElement
+	- ReadBackCompletion：碰撞数据GPU回读是否完成。
 
 
 ```c++
@@ -230,6 +229,7 @@ void AShaderWorldActor::CollisionManagement(float& DeltaT)
 ```
 
 #### SetupCollisions()
+设置相关变量。
 ```c++
 bool AShaderWorldActor::SetupCollisions()
 {
@@ -356,7 +356,7 @@ bool AShaderWorldActor::CollisionFinalizeWork()
 
 void UShaderWorldCollisionComponent::UpdateSectionTriMesh(TSharedPtr<FSWShareableVerticePositionBuffer, ESPMode::ThreadSafe>& Positions)
 {	
-	//UBodySetup
+	//当UBodySetup更新队列还有任务时，执行改函数会将FSWShareableVerticePositionBuffer加入到UpdatesReceivedDuringCompute数组中并且退出。
 	if (AsyncBodySetupQueue.Num() > 0)
 	{
 #if SWDEBUG
@@ -370,7 +370,7 @@ void UShaderWorldCollisionComponent::UpdateSectionTriMesh(TSharedPtr<FSWShareabl
 	
 	UpdatesReceivedDuringCompute.Empty();
 	
-
+	//使用FSWShareableVerticePositionBuffer数据来更新当前UShaderWorldCollisionComponent
 	bool EnsureSameBuffers = ProcMeshSections.Num() > 0 && ProcMeshSections[0].PositionBuffer.IsValid() && (ProcMeshSections[0].PositionBuffer->Positions3f.Num() == 0 || ProcMeshSections[0].PositionBuffer->Positions3f.Num() == Positions->Positions.Num());
 	if(!EnsureSameBuffers)
 	{
@@ -398,6 +398,7 @@ void UShaderWorldCollisionComponent::UpdateSectionTriMesh(TSharedPtr<FSWShareabl
 						{
 							if (UShaderWorldCollisionComponent* Comp = Cast<UShaderWorldCollisionComponent>(WeakThis.Get()))
 							{
+								//塞入Normal
 								if(IsValid(Comp))
 									Comp->ReceiveComputedNormals(PBuffer, Normals);
 							}
@@ -408,8 +409,8 @@ void UShaderWorldCollisionComponent::UpdateSectionTriMesh(TSharedPtr<FSWShareabl
 	
 	//Materials
 	// Pass new positions to trimesh
-	UpdateCollision();
+	UpdateCollision();//1. 异步Cook UBodySetup 2. 删除原本的碰撞 3. UseBodySetup->CreatePhysicsMeshesAsync()，使用UBodySetup异步创建新的碰撞网格。
-	UpdateLocalBounds();		 // Update overall bounds
+	UpdateLocalBounds();//更新UShaderWorldCollisionComponent的LocalBoundingBox
 	UpdateNavigation();
 
 	if (ProcMeshSections.Num() > 0 && (ProcMeshSections[0].bSectionVisible || (GetWorld() && !GetWorld()->IsGameWorld())))
@@ -423,6 +424,7 @@ void UShaderWorldCollisionComponent::UpdateSectionTriMesh(TSharedPtr<FSWShareabl
 			SectionData->TargetSection = 0;
 			SectionData->NewPositionBuffer = ProcMeshSections[0].PositionBuffer;
 
+			//更新SceneProxy FShaderWProceduralMeshSceneProxy的NewPositionBuffer，也就是UpdateSection
 			if(AShaderWorldActor* owner = Cast<AShaderWorldActor>(GetOwner()))
 			{
 				{
@@ -450,6 +452,192 @@ void UShaderWorldCollisionComponent::UpdateSectionTriMesh(TSharedPtr<FSWShareabl
 	}
 }
 ```
+
+#### CollisionPreprocessGPU()
+GPU生成碰撞 的预处理阶段。
+```c++
+bool AShaderWorldActor::CollisionPreprocessGPU()
+{
+	SCOPED_NAMED_EVENT_TEXT("AShaderWorldActor::CollisionPreprocessGPU()", FColor::Magenta);
+	SW_FCT_CYCLE()
+
+	for (int32 CollID = CollisionReadToProcess.Num() - 1; CollID >= 0; CollID--)
+	{
+		const FName& ElID = CollisionReadToProcess[CollID];
+
+
+		if (!CollisionMesh.Find(ElID))
+		{
+			CollisionWorkQueue.Empty();
+			CollisionReadToProcess.RemoveAt(CollID);
+			continue;
+		}
+
+		//判断FCollisionMeshElement是否有效，以及是否将碰撞数据回读完成，如果完成，则将数据添加到碰撞处理队列CollisionWorkQueue，并且从碰撞回读队列CollisionReadToProcess
+		FCollisionMeshElement& Mesh = *CollisionMesh.Find(ElID);
+		if ((*Mesh.ReadBackCompletion.Get()))
+		{
+			ensure(Mesh.Mesh);
+
+			if(FGeoCProcMeshSection* Section = Mesh.Mesh->GetProcMeshSection(0))
+			{
+				if(CollisionMesh.Contains(CollisionBufferHolder))
+				{
+					CollisionWorkQueue.Emplace(
+						ElID
+						, Mesh.HeightData
+						, (*CollisionMesh.Find(CollisionBufferHolder)).Mesh->VerticesTemplate
+						, (*CollisionMesh.Find(CollisionBufferHolder)).Mesh->TrianglesTemplate);
+				}
+				else
+				{
+					SW_LOG("!CollisionMesh.Contains(CollisionBufferHolder)")
+				}
+
+			}
+			else
+			{
+				SW_LOG("CollisionPreprocessGPU :: Mesh.Mesh->GetProcMeshSection(0) = nullptr")
+			}
+
+			
+			CollisionReadToProcess.RemoveAt(CollID);
+		}
+	}
+
+	if (!CollisionReadToProcess.IsEmpty())
+	{
+		return false;
+	}
+
+
+	CollisionReadToProcess.Empty();
+
+	if (CollisionWorkQueue.Num() > 0)
+	{
+		(*bProcessingGroundCollision.Get()) = true;
+
+		AShaderWorldActor* SWContext = this;
+
+		Async(EAsyncExecution::TaskGraph, [Completion = bProcessingGroundCollision, RenderAPI = RendererAPI, VerticesPerPatch = CollisionVerticesPerPatch, Work = CollisionWorkQueue]
+			{
+
+				ParallelFor(Work.Num(), [&](int32 WorkIndex)
+					{						
+						
+						const FCollisionProcessingWork& WorkEl = Work[WorkIndex];
+
+
+						if (!WorkEl.Read.IsValid() || !WorkEl.SourceB.IsValid() || !WorkEl.DestB.IsValid())
+							return;
+
+						const int NumOfVertex = WorkEl.SourceB->Positions.Num();
+
+						WorkEl.DestB->Positions.SetNum(NumOfVertex);
+						WorkEl.DestB->Positions3f.SetNum(NumOfVertex);
+						WorkEl.DestB->MaterialIndices.SetNum(NumOfVertex);
+						WorkEl.DestB->Bound = FBox(EForceInit::ForceInit);
+
+						FVector LocationfVertice_WS(0);
+						uint16 MaterialIndice = 0;
+
+						uint8* ReadData8 = (uint8*)WorkEl.Read->ReadData.GetData();
+
+						TSet<int32>& TrianglesAffectedByHoles = WorkEl.DestB->TrianglesAffectedByHoles;
+						TrianglesAffectedByHoles.Empty();
+
+						//#TODO ISPC slower ?
+#if 0 // INTEL_ISPC
+							if (RenderAPI == EGeoRenderingAPI::OpenGL)
+							{
+								ispc::ShaderWorld_HeightFromGPUReadOpenGL(NumOfVertex, VerticesPerPatch, ReadData8,(ispc::FVector*)WorkEl.SourceB->Positions.GetData(), (ispc::FVector*)WorkEl.DestB->Positions.GetData(), (ispc::FVector3f*)WorkEl.DestB->Positions3f.GetData(), WorkEl.DestB->MaterialIndices.GetData());
+								
+							}
+							else
+							{
+								ispc::ShaderWorld_HeightFromGPURead(NumOfVertex, VerticesPerPatch, ReadData8, (ispc::FVector3f*)WorkEl.SourceB->Positions3f.GetData(), (ispc::FVector*)WorkEl.DestB->Positions.GetData(), (ispc::FVector3f*)WorkEl.DestB->Positions3f.GetData(), WorkEl.DestB->MaterialIndices.GetData());
+							}
+#else
+
+						
+						for (int32 k = 0; k < NumOfVertex; k++)
+							{
+
+								if (RenderAPI == EGeoRenderingAPI::OpenGL)
+								{
+									const int index = k % VerticesPerPatch + (VerticesPerPatch - 1 - (k / VerticesPerPatch)) * VerticesPerPatch;
+
+									LocationfVertice_WS = FVector(WorkEl.SourceB->Positions[k].X, WorkEl.SourceB->Positions[k].Y, GetHeightFromGPURead(&ReadData8[4 * index], MaterialIndice));
+								}
+								else
+									LocationfVertice_WS = FVector(WorkEl.SourceB->Positions[k].X, WorkEl.SourceB->Positions[k].Y, GetHeightFromGPURead(&ReadData8[4 * k], MaterialIndice));
+
+								WorkEl.DestB->Positions[k] = LocationfVertice_WS;
+								WorkEl.DestB->Positions3f[k] = FVector3f(LocationfVertice_WS);
+								WorkEl.DestB->MaterialIndices[k] = MaterialIndice;
+
+								
+								/*
+								 * Height below -7km means terrain hole
+								 */
+								if(WorkEl.DestB->Positions[k].Z < -700000.0)
+								{
+									/*
+									 * Find triangles including this vertex and add them to removed triangles
+									 */
+
+									if(WorkEl.SourceB->PositionToTriangle.Contains(k))
+									{
+										TrianglesAffectedByHoles.Append(*WorkEl.SourceB->PositionToTriangle.Find(k));
+									}
+								}
+								else
+								{
+									WorkEl.DestB->Bound += WorkEl.DestB->Positions[k];
+								}
+							}
+
+#endif
+						/*
+						 * If the terrain has holes, create a custom index buffer with the related triangles removed
+						 */
+						if(TrianglesAffectedByHoles.Num() > 0)
+						{
+							WorkEl.DestB->FilteredTriangles = MakeShared<FSWShareableIndexBuffer, ESPMode::ThreadSafe>();
+
+							for(int32 Triangle = 0; Triangle < WorkEl.TriangleTemplate->Indices.Num()/3; Triangle++)
+							{
+								if(!TrianglesAffectedByHoles.Contains(Triangle))
+								{
+									WorkEl.DestB->FilteredTriangles->Indices.Add(WorkEl.TriangleTemplate->Indices[Triangle * 3]);
+									WorkEl.DestB->FilteredTriangles->Indices.Add(WorkEl.TriangleTemplate->Indices[Triangle * 3 + 1]);
+									WorkEl.DestB->FilteredTriangles->Indices.Add(WorkEl.TriangleTemplate->Indices[Triangle * 3 + 2]);
+
+									WorkEl.DestB->FilteredTriangles->Triangles_CollisionOnly.Add(WorkEl.TriangleTemplate->Triangles_CollisionOnly[Triangle]);
+								}
+							}
+						}
+						else
+						{
+							WorkEl.DestB->FilteredTriangles.Reset();
+						}
+
+
+						//WorkEl.DestB->Bound = FBox(WorkEl.DestB->Positions);
+					}
+				);
+
+				if (Completion.IsValid())
+					Completion->AtomicSet(false);
+
+			});
+	}
+
+	return true;
+}
+```
+
+
 ### SpawnablesManagement()
 
 ### TerrainAndSpawnablesManagement()