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02-Note/DAWA/2024.12.31新项目笔记.md

@@ -31,9 +31,82 @@
 
 
 # FaceSet
-https://groups.google.com/g/alembic-discussion/c/hICfVMzRV2U?pli=1
+https://github.com/zenustech/zeno/blob/b4ed8740810f20cf0612d615d9505468b2d2a4d1/projects/FBX/FBXSDK.cpp#L477
 
-FbxSelectionSet Class
+```c++
-https://help.autodesk.com/view/FBX/2015/ENU/?guid=__cpp_ref_class_fbx_selection_set_html
+int mat_count = 0;
+if (pMesh->GetElementMaterialCount() > 0) {
+	for (auto i = 0; i < numPolygons; ++i) {
+		faceset[i] = pMesh->GetElementMaterial()->GetIndexArray().GetAt(i);
+	}
+	mat_count = pNode->GetMaterialCount();
+	for (auto i = 0; i < mat_count; i++) {
+		FbxSurfaceMaterial* material = pNode->GetMaterial(i);
+		ud.set2(format("faceset_{}", i), material->GetName());
+	}
+}
+```
 
-GetPolygonGroup?
+UE中相关逻辑位于FbxMesh.cpp
+```c++
+void ExtractMeshMaterials(FFbxParser& Parser, FbxMesh* Mesh, FbxNode* MeshNode, TFunction<void(const FString& MaterialName, const FString& MaterialUid, const int32 MeshMaterialIndex)> CollectMaterial)
+	{
+		if (!Mesh || !MeshNode)
+		{
+			return;
+		}
+
+		//Grab all Material indexes use by the mesh
+		TArray<int32> MaterialIndexes;
+		int32 PolygonCount = Mesh->GetPolygonCount();
+		if (FbxGeometryElementMaterial* GeometryElementMaterial = Mesh->GetElementMaterial())
+		{
+			FbxLayerElementArrayTemplate<int32>& IndexArray = GeometryElementMaterial->GetIndexArray();
+			switch (GeometryElementMaterial->GetMappingMode())
+			{
+			case FbxGeometryElement::eByPolygon:
+			{
+				if (IndexArray.GetCount() == PolygonCount)
+				{
+					for (int32 PolygonIndex = 0; PolygonIndex < PolygonCount; ++PolygonIndex)
+					{
+						MaterialIndexes.AddUnique(IndexArray.GetAt(PolygonIndex));
+					}
+				}
+			}
+			break;
+
+			case FbxGeometryElement::eAllSame:
+			{
+				if (IndexArray.GetCount() > 0)
+				{
+					MaterialIndexes.AddUnique(IndexArray.GetAt(0));
+				}
+			}
+			break;
+			}
+		}
+		const int32 MaterialCount = MeshNode->GetMaterialCount();
+		TMap<FbxSurfaceMaterial*, int32> UniqueSlotNames;
+		UniqueSlotNames.Reserve(MaterialCount);
+		bool bAddAllNodeMaterials = (MaterialIndexes.Num() == 0);
+		for (int32 MaterialIndex = 0; MaterialIndex < MaterialCount; ++MaterialIndex)
+		{
+			if (FbxSurfaceMaterial* FbxMaterial = MeshNode->GetMaterial(MaterialIndex))
+			{
+				int32& SlotMaterialCount = UniqueSlotNames.FindOrAdd(FbxMaterial);
+				FString MaterialName = Parser.GetFbxHelper()->GetFbxObjectName(FbxMaterial);
+				FString MaterialUid = TEXT("\\Material\\") + MaterialName;
+				if (bAddAllNodeMaterials || MaterialIndexes.Contains(MaterialIndex))
+				{
+					if (SlotMaterialCount > 0)
+					{
+						MaterialName += TEXT("_Section") + FString::FromInt(SlotMaterialCount);
+					}
+					SlotMaterialCount++;
+					CollectMaterial(MaterialName, MaterialUid, MaterialIndex);
+				}
+			}
+		}
+	}
+```