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03-UnrealEngine/Gameplay/Mass/Mass扩展笔记.md

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+---
+title: Mass扩展笔记
+date: 2024-09-12 15:32:15
+excerpt: 
+tags: 
+rating: ⭐
+---
+# 
+1. 创建  UMassEntityTraitBase （UMassVisualizationTrait）
+2. 相关的渲染设置逻辑位于UMassVisualizationComponent。
+
+
+
+# UMassVisualizationComponent
+```c++
+
+void UMassVisualizationComponent::ConstructStaticMeshComponents()
+{
+	AActor* ActorOwner = GetOwner();
+	check(ActorOwner);
+	
+	UE_MT_SCOPED_WRITE_ACCESS(InstancedStaticMeshInfosDetector);
+	for (FMassInstancedStaticMeshInfo& Info : InstancedStaticMeshInfos)
+	{
+		// Check if it is already created
+		if (!Info.InstancedStaticMeshComponents.IsEmpty())
+		{
+			continue;
+		}
+
+		// Check if there are any specified meshes for this visual type
+		if(Info.Desc.Meshes.Num() == 0)
+		{
+			UE_LOG(LogMassRepresentation, Error, TEXT("No associated meshes for this intanced static mesh type"));
+			continue;
+		}
+		for (const FStaticMeshInstanceVisualizationMeshDesc& MeshDesc : Info.Desc.Meshes)
+		{			
+			FISMCSharedData* SharedData = ISMCSharedData.Find(MeshDesc);
+			UInstancedStaticMeshComponent* ISMC = SharedData ? SharedData->ISMC : nullptr;
+			if (SharedData)
+			{
+				SharedData->RefCount += 1;
+			}
+			else
+			{
+				ISMC = NewObject<UInstancedStaticMeshComponent>(ActorOwner);
+				ISMC->SetStaticMesh(MeshDesc.Mesh);
+				for (int32 ElementIndex = 0; ElementIndex < MeshDesc.MaterialOverrides.Num(); ++ElementIndex)
+				{
+					if (UMaterialInterface* MaterialOverride = MeshDesc.MaterialOverrides[ElementIndex])
+					{
+						ISMC->SetMaterial(ElementIndex, MaterialOverride);
+					}
+				}
+				ISMC->SetCullDistances(0, 1000000); // @todo: Need to figure out what to do here, either LOD or cull distances.
+				ISMC->SetupAttachment(ActorOwner->GetRootComponent());
+				ISMC->SetCanEverAffectNavigation(false);
+				ISMC->SetCollisionProfileName(UCollisionProfile::NoCollision_ProfileName);
+				ISMC->SetCastShadow(MeshDesc.bCastShadows);
+				ISMC->Mobility = MeshDesc.Mobility;
+				ISMC->SetReceivesDecals(false);
+				ISMC->RegisterComponent();
+
+				ISMCSharedData.Emplace(MeshDesc, FISMCSharedData(ISMC));
+			}
+
+			Info.InstancedStaticMeshComponents.Add(ISMC);
+		}
+
+		// Build the LOD significance ranges
+		TArray<float> AllLODSignificances;
+		auto UniqueInsertOrdered = [&AllLODSignificances](const float Significance)
+		{
+			int i = 0;
+			for (; i < AllLODSignificances.Num(); ++i)
+			{
+				// I did not use epsilon check here on purpose, because it will make it hard later meshes inside.
+				if (Significance == AllLODSignificances[i])
+				{
+					return;
+				}
+				if (AllLODSignificances[i] > Significance)
+				{
+					break;
+				}
+			}
+			AllLODSignificances.Insert(Significance, i);
+		};
+		for (const FStaticMeshInstanceVisualizationMeshDesc& MeshDesc : Info.Desc.Meshes)
+		{
+			UniqueInsertOrdered(MeshDesc.MinLODSignificance);
+			UniqueInsertOrdered(MeshDesc.MaxLODSignificance);
+		}
+		Info.LODSignificanceRanges.SetNum(AllLODSignificances.Num() - 1);
+		for (int i = 0; i < Info.LODSignificanceRanges.Num(); ++i)
+		{
+			FMassLODSignificanceRange& Range = Info.LODSignificanceRanges[i];
+			Range.MinSignificance = AllLODSignificances[i];
+			Range.MaxSignificance = AllLODSignificances[i+1];
+			Range.ISMCSharedDataPtr = &ISMCSharedData;
+
+			for (int j = 0; j < Info.Desc.Meshes.Num(); ++j)
+			{
+				const FStaticMeshInstanceVisualizationMeshDesc& MeshDesc = Info.Desc.Meshes[j];
+				const bool bAddMeshInRange = (Range.MinSignificance >= MeshDesc.MinLODSignificance && Range.MinSignificance < MeshDesc.MaxLODSignificance);
+				if (bAddMeshInRange)
+				{
+					Range.StaticMeshRefs.Add(MeshDesc);
+				}
+			}
+		}
+
+	}
+}
+```
+
+设置灯光通道：
+```c++
+void UPrimitiveComponent::SetLightingChannels(bool bChannel0, bool bChannel1, bool bChannel2)
+{
+	if (bChannel0 != LightingChannels.bChannel0 ||
+		bChannel1 != LightingChannels.bChannel1 ||
+		bChannel2 != LightingChannels.bChannel2)
+	{
+		LightingChannels.bChannel0 = bChannel0;
+		LightingChannels.bChannel1 = bChannel1;
+		LightingChannels.bChannel2 = bChannel2;
+		if (SceneProxy)
+		{
+			SceneProxy->SetLightingChannels_GameThread(LightingChannels);
+		}
+		MarkRenderStateDirty();
+	}
+}
+```