Inverted Mouth/Jaw BlendShapes in Live Link Face (LiveLink ARKit mode)

Development Character & Animation
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1

Hello Epic Developer Community,

I’m seeing unexpected behavior directly within the Live Link Face app, both in its preview UI and in the recorded CSV output.

  • Problems

    • MouthLeft / MouthRight, JawLeft / JawRight: when the actor moves their lips or jaw to their physical left, the recorded MouthRight and JawRight channels rise, and vice versa.
    • All other blendShapes: (e.g. EyeBlinkLeft/Right, MouthSmileLeft/Right, etc.) reflect the actor’s physical movements in actor-space.

  • Environment:

    • iOS Device: iPhone 15 Pro, iOS 18.5
    • Live Link Face App version: 1.4.2

  • Steps to reproduce in Live Link Face alone:

    1. Open Live Link Face on the device.
    2. Observe the real-time graph in the app preview as the actor moves their lips/jaw.
    3. Record or export the CSV from Live Link Face and inspect the raw values.
    4. Actor moves lips/jaw to their physical left → MouthRight and JawRight values increase.
    5. Actor moves lips/jaw to their physical right → MouthLeft and JawLeft values increase.

  • Notes:
    When tested using the Swing application, all blendShapes (including blink and smile) were inverted relative to actor-space.