class ViewController: UIViewController {
    var oldX: CGFloat = 0.0
    var oldY: CGFloat = 0.0

    override func viewDidLoad() {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
    }

    // 行列で回転 (片軸でしか回せなかった)
    @objc func handlePan(recognizer: UIPanGestureRecognizer) {
        let translation = recognizer.translation(in: view)

        // デバイスのサイズを2 * piにマップ
        let x = translation.x / view.frame.width * .pi * 2

        // 一つ前の値と合わせて更新する量を決める
        let newX = oldX + x
        shipNode?.rotation = SCNVector4(0, 1, 0, newX)
        recognizer.setTranslation(CGPoint.zero, in: view)
        oldX = newX
    }

    // オイラー角で回転
    @objc func handlePan(recognizer: UIPanGestureRecognizer) {
        let translation = recognizer.translation(in: view)

        let x = translation.x / view.frame.width * .pi * 2
        let y = translation.y / view.frame.width * .pi * 2

        let newX = oldX + x
        let newY = oldY + y

        shipNode?.eulerAngles.y = Float(newX)
        shipNode?.eulerAngles.x = Float(newY)

        recognizer.setTranslation(CGPoint.zero, in: view)

        oldX = newX
        oldY = newY
    }

    // Quaternionで回転
    // 古い値の保持は必要ない
    @objc func handlePan(recognizer: UIPanGestureRecognizer) {
        let translation = recognizer.translation(in: view)

        let x = translation.x / view.frame.width * .pi * 2
        let y = translation.y / view.frame.width * .pi * 2

        let qy = simd_quatf(angle: Float(x), axis: float3(0, 1, 0))
        let qx = simd_quatf(angle: Float(y), axis: float3(1, 0, 0))
        shipNode?.simdLocalRotate(by: qy)
        shipNode?.simdLocalRotate(by: qx)

        recognizer.setTranslation(CGPoint.zero, in: view)
    }
}