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November 12, 2022 17:13
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Determine the direction of "gaze" of the device in any orientation
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extension CMDeviceMotion { | |
func gaze(atOrientation orientation: UIInterfaceOrientation) -> SCNVector4 { | |
let attitude = self.attitude.quaternion | |
let aq = GLKQuaternionMake(Float(attitude.x), Float(attitude.y), Float(attitude.z), Float(attitude.w)) | |
let final: SCNVector4 | |
switch orientation { | |
case .landscapeRight: | |
let cq = GLKQuaternionMakeWithAngleAndAxis(Float.pi / 2, 0, 1, 0) | |
let q = GLKQuaternionMultiply(cq, aq) | |
final = SCNVector4(x: -q.y, y: q.x, z: q.z, w: q.w) | |
case .landscapeLeft: | |
let cq = GLKQuaternionMakeWithAngleAndAxis(-Float.pi / 2, 0, 1, 0) | |
let q = GLKQuaternionMultiply(cq, aq) | |
final = SCNVector4(x: q.y, y: -q.x, z: q.z, w: q.w) | |
case .portraitUpsideDown: | |
let cq = GLKQuaternionMakeWithAngleAndAxis(Float.pi / 2, 1, 0, 0) | |
let q = GLKQuaternionMultiply(cq, aq) | |
final = SCNVector4(x: -q.x, y: -q.y, z: q.z, w: q.w) | |
case .unknown: | |
fallthrough | |
case .portrait: | |
fallthrough | |
@unknown default: | |
let cq = GLKQuaternionMakeWithAngleAndAxis(-Float.pi / 2, 1, 0, 0) | |
let q = GLKQuaternionMultiply(cq, aq) | |
final = SCNVector4(x: q.x, y: q.y, z: q.z, w: q.w) | |
} | |
return final | |
} | |
} |
@travisnewby My math is very bad, could you please explain more detailed? Hopefully you can introduce the codes line by line, please forgive my foolishness.
@evanxlh The math is nothing more than applying a rotation – based on the orientation of your phone – to a vector. I can't explain the math as clearly as many of the youtube videos talking about quaternions for game developers. That's your best bet for understanding.
thank you for your "magic" extension.
@ostholz you’re welcome.
Thank you very much for this! Saves a lot of headaches!
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Done!