BlueRoseNote/03-UnrealEngine/Editor/FBXAnimation导入&导出逻辑.md

title, date, excerpt, tags, rating

title	date	excerpt	tags	rating
FBXAnimation导入逻辑	2023-12-11 11:28:36			⭐

BVHImport插件中的案例

UObject* UBVHImportFactory::FactoryCreateFile(UClass* InClass, UObject* InParent, FName InName, EObjectFlags Flags, const FString& FileName, const TCHAR* Parms, FFeedbackContext* Warn, bool& bOutOperationCanceled)
{
	if (!shouldImport) {
		return nullptr;
	}
	bool fileSuccess = BVHFile.ImportData(TCHAR_TO_ANSI(*FileName));
	
	const bool bIsUnattended = (IsAutomatedImport()
		|| FApp::IsUnattended()
		|| IsRunningCommandlet()
		|| GIsRunningUnattendedScript);

	// Check if it's a re-import
	if (InParent != nullptr)
	{
		UObject* ExistingObject = StaticFindObject(UObject::StaticClass(), InParent, *InName.ToString());
		if (ExistingObject)
		{
			//reimport逻辑略
		}
	}
	
	if (fileSuccess)
	{	
		UAnimSequence* AnimSequence = NewObject<UAnimSequence>(InParent, InName, Flags & ~EObjectFlags::RF_Transactional);
		if (Skeleton == NULL) {
			//创建骨骼资产略
		}
		else {
			AnimSequence->SetSkeleton(Skeleton);//Skeleton bvhSkel
			AnimSequence->SetPreviewMesh(PreviewMesh);			
		}
		ExtractAnimDataFromBVHFile(AnimSequence);
		return AnimSequence;
		
	}
	return nullptr;
	
}

void UBVHImportFactory::ExtractAnimDataFromBVHFile(UAnimSequence* AnimSequence) {
	if (AnimSequence)
	{		
		// create animation		
		IAnimationDataController& Controller = AnimSequence->GetController();
		Controller.OpenBracket(LOCTEXT("ImportBVHAnimation", "Importing BVH Animation"));
		Controller.ResetModel();

		// Write animation data into animation sequence.
		// Extract transform of hip to create root motion.
		const FReferenceSkeleton& RefSkeleton = AnimSequence->GetSkeleton()->GetReferenceSkeleton();
		const FName RootName = RefSkeleton.GetBoneName(0);
		const int32 NumOfKeys = BVHFile.Root->FrameOffset.Num();

		AnimSequence->ImportFileFramerate = (float)BVHFile.Header.DataRate;
		AnimSequence->ImportResampleFramerate = BVHFile.Header.DataRate;

		Controller.SetPlayLength(float(NumOfKeys - 1) / (float)BVHFile.Header.DataRate);
		Controller.SetFrameRate(FFrameRate(BVHFile.Header.DataRate, 1));
		
		RecursiveReadKeysFromNode(Controller, BVHFile.Root.Get());

		Controller.NotifyPopulated();
		Controller.CloseBracket();

		AnimSequence->AdditiveAnimType = EAdditiveAnimationType::AAT_None;
		AnimSequence->PostEditChange();
		FAssetRegistryModule::AssetCreated(AnimSequence);
		AnimSequence->MarkPackageDirty();
	}
}

void UBVHImportFactory::RecursiveReadKeysFromNode(IAnimationDataController& Controller, FNode* Node)
{
	if (Node)
	{
		Controller.AddBoneTrack(Node->Name,false);
		Controller.SetBoneTrackKeys(Node->Name, Node->FrameOffset, Node->FrameQuat, Node->FrameScale,false);
		if (Node->Children.Num() > 0)
		{
			for (NodePtr Child : Node->Children)
			{
				RecursiveReadKeysFromNode(Controller, Child.Get());
			}
		}
	}
}

UE5中使用FBXSDK导入动画逻辑

• UAnimSequence * UEditorEngine::ImportFbxAnimation
  • UAnimSequence * UnFbx::FFbxImporter::ImportAnimations

UE5中FBXSDK相关函数调用方式：

• bool FFbxImporter::OpenFile(FString Filename)
• bool FFbxImporter::ImportFile(FString Filename, bool bPreventMaterialNameClash /=false/)

参考

1. Interchange\Runtime\Source\Parsers
   1. InterchangeFbxParser.Build.cs
   2. FbxInclude.h：FBXSDK头文件包含问题。

UE5中使用FBXSDK导出动画逻辑

1. FFbxExporter::ExportSkeletalMeshToFbx => FFbxExporter::ExportAnimSequence => FFbxExporter::ExportAnimSequenceToFbx
2. FFbxExporter::CorrectAnimTrackInterpolation

直接导出会有问题，所以UE在这里做了一步Correct：

// The curve code doesn't differentiate between angles and other data, so an interpolation from 179 to -179  
// will cause the bone to rotate all the way around through 0 degrees. So here we make a second pass over the  
// rotation tracks to convert the angles into a more interpolation-friendly format.
FFbxExporter::CorrectAnimTrackInterpolation()
{
void FFbxExporter::CorrectAnimTrackInterpolation( TArray<FbxNode*>& BoneNodes, FbxAnimLayer* InAnimLayer )
{
	// Add the animation data to the bone nodes
	for(int32 BoneIndex = 0; BoneIndex < BoneNodes.Num(); ++BoneIndex)
	{
		FbxNode* CurrentBoneNode = BoneNodes[BoneIndex];

		// Fetch the AnimCurves
		FbxAnimCurve* Curves[3];
		Curves[0] = CurrentBoneNode->LclRotation.GetCurve(InAnimLayer, FBXSDK_CURVENODE_COMPONENT_X, true);
		Curves[1] = CurrentBoneNode->LclRotation.GetCurve(InAnimLayer, FBXSDK_CURVENODE_COMPONENT_Y, true);
		Curves[2] = CurrentBoneNode->LclRotation.GetCurve(InAnimLayer, FBXSDK_CURVENODE_COMPONENT_Z, true);

		for(int32 CurveIndex = 0; CurveIndex < 3; ++CurveIndex)
		{
			FbxAnimCurve* CurrentCurve = Curves[CurveIndex];
			CurrentCurve->KeyModifyBegin();

			float CurrentAngleOffset = 0.f;
			for(int32 KeyIndex = 1; KeyIndex < CurrentCurve->KeyGetCount(); ++KeyIndex)
			{
				float PreviousOutVal	= CurrentCurve->KeyGetValue( KeyIndex-1 );
				float CurrentOutVal		= CurrentCurve->KeyGetValue( KeyIndex );

				float DeltaAngle = (CurrentOutVal + CurrentAngleOffset) - PreviousOutVal;

				if(DeltaAngle >= 180)
				{
					CurrentAngleOffset -= 360;
				}
				else if(DeltaAngle <= -180)
				{
					CurrentAngleOffset += 360;
				}

				CurrentOutVal += CurrentAngleOffset;

				CurrentCurve->KeySetValue(KeyIndex, CurrentOutVal);
			}

			CurrentCurve->KeyModifyEnd();
		}
	}
}

导入Curve相关逻辑

UnFbx::FFbxImporter::ImportCurveToAnimSequence() => UnFbx::FFbxImporter::ImportCurve()