Track Eyebrows & Blinks | raywenderlich.com

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Use the movement of a user’s eyes and eyebrows to drive the eyelid animation of a 3D robot head! Apply multiple rotations to a single object.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/20591636-face-tracking-with-realitykit/lessons/8
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Hi Catie - great tutorial so far! I had a question if you had a moment to answer…

I’m unable to get my eyelid to rotate around the z-axis. I’ve created my own robot and I’m able to successfully get the eyelid to blink as expected. But once I introduce the z-axis, it continues to blink, but never rotates around the z-axis.

Here’s my code:

robot.topLidL?.orientation = simd_mul(
            simd_quatf(angle: deg2rad(-80 + (130 * eyeBlinkLeft)), axis: [1, 0, 0]),
            simd_quatf(angle: deg2rad((130 * browLeft) - (60 * browInnerUp)), axis: [0, 0, 1])) // z-axis

I get 0 movement at all around the z-axis. I downloaded your example, and it does in fact work. I confirmed that I am getting values from browLeft and browInnerUp. I looked at the assets in Reality Composer and all looks well. An interesting note is if I change the Z value in Reality Composer, I do see the rotation in Composer as I would expect.

I also just tried

robot.topLidL?.orientation = simd_quatf(angle: deg2rad((130 * browLeft) - (60 * browInnerUp)), axis: [0, 0, 1])

and that doesn’t work either. I even just hardcoded:

robot.topLidL?.orientation = simd_quatf(angle: deg2rad(50), axis: [0, 0, 1])

And even that didn’t cause any change.

Simply put, I’m getting no movement at all around the z-axis.

Do you have any ideas why this might be the case?

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Hey Alan! That is odd. My first guess is that there is an axis misalignment going on since you made your own robot. What happens when you rotate around the y-axis via code? I’m happy to take a look at your project if you have a way to share it with me.