BUG: FAnimNode_PoseBlendNode holds old curve values

Development Character & Animation
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1

In our project we noticed that character faces were getting stuck when we transitioned them from one animation to another. We looked into it and found the culprit was in FAnimNode_PoseBlendNode::Evaluate_AnyThread. It appears when doing the BulkGet to set the new curve values, it never resets the old curve values. So if animation A uses one set of curves and B uses another, when you move to animation B all of A’s curve values will still be present. We fixed this by doing the following:

if (CachedPoseAsset && PoseExtractContext.PoseCurves.Num() > 0 && CachedPoseAsset->GetSkeleton() != nullptr)
{
	FPoseContext CurrentPose(Output);

	// ENGINE_MOD - Reset all curve values so no leftover data from a different source anim is carried forward
	for (FPoseCurve& curve : PoseExtractContext.PoseCurves)
	{
		curve.Value = 0.0f;
	}
	// ENGINE_MOD

	// Remap incoming curve
	UE::Anim::FCurveUtils::BulkGet(SourceData.Curve, BulkCurves, [this](const UE::Anim::FNamedIndexElement& InBulkElement, float InValue)
	{
		// Remap using chosen BlendOption
		const float RemappedValue = FAlphaBlend::AlphaToBlendOption(InValue, BlendOption, CustomCurve);
		PoseExtractContext.PoseCurves[InBulkElement.Index].Value = RemappedValue;
        });

This fixed our issue and cleared out the old values. Is this a known issue on your end?

Thanks!

2

Hey there,

This is a known issue and by design. If the code above works for you, that is fine. We also added another node, FAnimNode_RemoveCurve, that you can run before this one if you want to perform a similar operation.

Dustin

3

Ah ok. We are not on 5.7 yet so we do not have access to that anim node. Once we upgrade we may revisit.

Thanks!