ARFaceAnchor.BlendShapeLocation browOuterUp* not tracked separately left to right

I am using swift under Xcode 10.2 and building to an iPhone Xs running iOS 12.2


ARFaceAnchor.BlendShapeLocation browOuterUp* coefficients aren't being tracked and/or reported separately, left to right. That is, there is nearly no difference in the reported value of browOuterUpLeft/browOuterUpRight at runtime, no matter waht the user's facial pose is. I have tested this on four separate users who all have the ability to separately move their eyebrows. It appears to be getting the value from the left brow and reporting it as both left and right values.


I am pulling and logging these coefficients from the ARFaceAnchor in the scene, during the SCNSceneRenderer render step. All of the other left/right coefficient pairs show left-to right discrepancy corresponding to the user pose.


I am wondering if anyone else can either confirm that these brow coefficients are indeed not being differentiated left to right, or if they can definitively report the ability to track them separately. Would be great to have someone on the Apple ARKit team take a look as well, as this may be a fundamental bug.

Post not yet marked as solved Up vote post of turdpolisher Down vote post of turdpolisher
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Hello is anyone monitoring this forum?

It appears that these particular blendShapes are not being updated completely independently, if you think this is a bug, or if you would like this to be enhanced, please file a bug report at https://developer.apple.com/bug-reporting/

Hi thanks for the reply. It does seem like a bug, as all of the other left/right tracking reports independantly as expected. I've reported it as a bug about two weeks ago (with an example swift file), #50611765, but no one is replying there either, although someone did mark it as a dupe of a bug which I assume is far older based on the numbering #37234600, but I have no way to see the contents of that bug to see if it's actually the same. I inquired about that as well, but no one responded to that either. Although if that numbering is a real indicator of the number of reported bugs, I should probably give up and switch platforms 🙂

Hi, do you know if there is any way to get anyone to respond to the bug I posted? It's been three weeks and no one has replied.

Hello can anyone from Apple comment on this bug and a timeframe for getting it resolved?

I am experiencing the same issue via Unity's ARKit Face Tracking package, Version 3.1.7 - October 20, 2020.

I see this behavior in the float values of the blendshapes, as well as in the default blendshape animation example: The 3D face asset is clearly raising both brows when I raise my Left brow.

Is this a known bug? If so, is there an ETA? Thank you.