How to rotate and lock the rotation of a SCNNode by degrees?

I need to rotate a model that can be freely rotated, to exact degrees, regardless of how many times it's been rotated.

I have a UIPanGestureRecognizer that is rotating freely a 3D model around the Y axis. However I'm struggling to get it to lock to a integer degree when panning is stopped, and I'm struggling with being able to know it's rotation in degrees from 0-359.

let translation = recognizer.translation(in: self.view)

var newAngleY = Double(translation.x) * (Double.pi) / 180.0
newAngleY += self.currentAngle

self.shipNode?.eulerAngles.y = Float(newAngleY)

if (recognizer.state == .ended)
{
   self.currentAngle = newAngleY
}

It rotates freely, but all attempts for locking to the closest exact degree, and being able to 'know' it's rotational degree in a value from 0-359.

I know that:

let degrees = newAngleY * ( 180 / Double.pi)

And I know that if degrees > 360 then -= 360 (pseudo code)

However, whilst the UIPanGestureRecognizer is doing it's thing, these checks seem to fail and I don't know why. Is it because when it's still being panned, you can't edit the private properties of the ViewController?

Solution

You can edit the value while the gesture is occurring.

Quite a few options, so this seems the simplest to start with:

You could try only applying euler when the state changes AND only when .x > .x * (some value, such as 1.1). This would provide a more "snap to" kind of approach, something like:

 var currentLocation = CGPoint.zero
 var beginLocation = CGPoint.zero

 @objc func handlePan(recognizer: UIPanGestureRecognizer) {
    currentLocation = recognizer.location(in: gameScene)

    var newAngleY = Double(translation.x) * (Double.pi) / 180.0
    newAngleY += self.currentAngle

    switch recognizer.state
    {
     case UIGestureRecognizer.State.began: break
     case UIGestureRecognizer.State.changed:
         if(currentLocation.x > beginLocation.x * 1.1)
         {
           gNodes.bnode.eulerAngles.y = Float(newAngleY)
           beginLocation.x = currentLocation.x
         }
         if(currentLocation.x < beginLocation.x * 0.9) { .etc. }
         break
         case UIGestureRecognizer.State.ended:
           gNodes.bnode.eulerAngles.y = Float(newAngleY)
           break
    }
}

Then you could switch to an SCNAction (changing your math) to give more control, such as

let vAction = SCNAction.rotateTo(x: 0, y: vAmount, z: 0, duration: 0)
bnode.runAction(vAction)