Question

我使用以下行旋转SCNNode：

 let rotate = SCNAction.rotateByAngle(CGFloat(M_PI), aroundAxis:SCNVector3Make(0, 1, 0), duration: NSTimeInterval(10.0))
    let repeat = SCNAction.repeatActionForever(rotate)
    node.runAction(repeat)

然后我在render方法中打印节点的eulerAngles.y：

let rad = Double(node.eulerAngles.y)        
var angleInDegrees = fmodf(360.0 + -Float(rad) * (180.0 / Float(M_PI)), 360.0)
println("eulerAngles.y rad:\(rad) degree:\(angleInDegrees)")

但是我在旋转期间会得到奇怪的值，如下所示：

...
eulerAngles.y rad:-1.38788688182831 degree:79.5201
eulerAngles.y rad:-1.40567290782928 degree:80.5391 
eulerAngles.y rad:-1.4227991104126 degree:81.5204
eulerAngles.y rad:-1.44030773639679 degree:82.5236
eulerAngles.y rad:-1.45790004730225 degree:83.5315
eulerAngles.y rad:-1.47438871860504 degree:84.4763
eulerAngles.y rad:-1.49130213260651 degree:85.4453
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:1.57079637050629 degree:270.0
eulerAngles.y rad:-1.49359321594238 degree:85.5766
eulerAngles.y rad:-1.47716772556305 degree:84.6355
...

我不明白为什么要打印270。你能用其他方式解释我吗？获得节点的正确角度？

Answer 1

这就是欧拉角度的工作方式。他们有两个怪癖（我将x，y和z分别称为pitch，yaw和roll：

roll和yaw随着逆时针旋转从0增加到π（180度），然后跳转到-π（-180度）并随着旋转完成继续增加到0一个圆圈;但pitch增加到π/ 2（90度）然后减小到0，然后减少到-π/ 2（-90度）并增加到0.
值在某些方向上变得不准确。特别是，当pitch为±90度时，roll和yaw变得不稳定。请参阅wikipedia article on gimbal lock。

ScenKit eulerAngles旋转期间的奇怪值

1 个答案: