Tool tips for ue4 animation programming

This article mainly focus on some tool-tips you might encounter while doing some animation development. And I will keep updating this article from time to time.

AnimNode not evaluating your data?

If you have your own Animation Node and find it not evaluate your input data?

In your Update_AnyThread function, be sure to call:

GetEvaluateGraphExposedInputs().Execute(Context)

Caution: This shall cost some performance!

FCSPose::ConvertBoneLocalSpace Function

Bone hierarchy is an array-based tree. Thus if you want to convert all bone to local space, be sure to traverse from end to the beginning.

Don’t use TMap for your own AnimNode

Well… at lease not in 4.20
Using TMap causing crash when hitting compile button or save.

// FAnimBlueprintCompilerContext::CreateEvaluationHandlerStruct
// Does it get serviced by this handler?
		if (FAnimNodeSinglePropertyHandler* SourceInfo = Record.ServicedProperties.Find(PropertyName))
		{
			if (TargetPin->PinType.IsArray())
			{
				// ... 
			}
			else
			{
				// Causing crash here. 
				check(!TargetPin->PinType.IsContainer())
				// ...
			}
		}

Watch out out bone order in your EvaluateSkeletalControl_AnyThread function.

See FCSPose<PoseType>::LocalBlendCSBoneTransforms function. There is a Parents before Children order check in this function.

template<class PoseType>
void FCSPose<PoseType>::LocalBlendCSBoneTransforms(const TArray<struct FBoneTransform>& BoneTransforms, float Alpha)
{
	SCOPE_CYCLE_COUNTER(STAT_LocalBlendCSBoneTransforms);

	// if Alpha is small enough, skip
	if (Alpha < ZERO_ANIMWEIGHT_THRESH)
	{
		return;
	}

#if DO_CHECK
	if (BoneTransforms.Num() > 0)
	{
		FCompactPoseBoneIndex LastIndex(BoneTransforms[0].BoneIndex);
		// Make sure bones are sorted in "Parents before Children" order.
		for (int32 I = 1; I < BoneTransforms.Num(); ++I)
		{
			check(BoneTransforms[I].BoneIndex >= LastIndex);
			LastIndex = BoneTransforms[I].BoneIndex;
		}
	}
#endif
    ...

As a result, do add following code to the end of your function:

OutBoneTransforms.Sort(FCompareBoneTransformIndex());

How to get curve data in an Anim Sequence?

Before Version 4.22:

const auto& curveData = inAnimSeq->GetCurveData();

auto curveUID = inAnimSeq->GetSkeleton()->GetUIDByName(USkeleton::AnimCurveMappingName, inCurveName);

if (curveUID == SmartName::MaxUID)
{
	success = false;
	return errorResult;
}
const FFloatCurve* curve = (const FFloatCurve*)curveData.GetCurveData(curveUID, ERawCurveTrackTypes::RCT_Float);

success = true; 
float result = curve->Evaluate(inTime);
return result;

After Version 4.22:

auto curveUID = inAnimSeq->GetSkeleton()->GetUIDByName(USkeleton::AnimCurveMappingName, inCurveName);

if (curveUID == SmartName::MaxUID)
{
	success = false;
	return errorResult;
}

return inAnimSeq->EvaluateCurveData(curveUID, inTime);

AnimGraphNode Module

Your AnimGraphNode should be placed in a Developer or Uncooked module. Otherwise it cause error in your dedicated server.