Why is my bone rotation flipping / being clamped?

Development Character & Animation
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1

I am pretty new to Unreal and I’ve come up against an issue that I am struggling to resolve.

I am trying to modify the rotation of a bone in the AnimGraph, and it works as expected to a point. The problem I’m having is that once the bone has rotated past a certain (seemingly arbitrary) threshold it will “flip” unexpectedly.

I’m modifying the bone using a Transform (Modify) Bone node, creating an FRotator using input from an axis (the input is unclamped):

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Interestingly, if I modify the rotation manually in the transform details panel, it will rotate smoothly and infinitely without ever flipping. However as soon as I rotate using either the gizmo or by piping a value into the anim graph the flipping issue appears. It’s as if the bone rotation is being clamped automatically without me ever asking it to, and I can’t find a way to bypass this behaviour.

2

It might be because of gimbal lock, meaning that after reaching +180 it’ll flip to -180.
The solution is to use Quaternions, and in UE5 they’re exposed in the Animgraph.

3

Hey - thanks for the reply.

When you say “use Quaternions” can you explain how please?

I’ve tried to play around with the Make Quat node instead of what I was doing, but I have a similar issue in that the FRotator I have to convert to simply refuses to rotate any further than 180

It seems to me that the real issue is the Transform (Modify) Bone node which appears to be triggering the clamped behaviour, but I have no idea how to bypass that or what other method to use instead (assuming there is one).

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1 Like
4

I’m having this same exact issue. Were you ever able to figure it out?