SceneKit: pan gesture not storing previous rotation

Question

I am using a pan gesture to rotate a node in my SceneKit Scene. The code I currently have rotates the node perfectly. Here is my code I am using to rotate the node:

var previousRotation:Float = 0

@objc func panGestureRecognized(gesture: UIPanGestureRecognizer) {
    if gesture.numberOfTouches == 2 {
        let view = self.view as! SCNView
        let node = view.scene!.rootNode.childNode(withName: "Node", recursively: false)
        let translation = gesture.translation(in: view)

        var newAngle = Float(translation.x) * Float(Double.pi) / 180.0
        newAngle += previousRotation

        switch gesture.state {
        case .began:
            newAngle += previousRotation
            break
        case .changed:
            node!.rotation = SCNVector4(x: 0, y: Float(translation.y), z: 0, w: newAngle)
            break
        case .ended:
            newAngle += previousRotation
            break
        default: break
        }
    }
}

The problem is, the rotation "resets" when you lift your fingers and start the rotation again. I need it to "keep" its rotation so when you start panning again it just continues from where the last rotation stopped at.

this code never sets the previousRotation variable. Shouldn't it be previousRotation = newAngle in the .ended case? — mnuages
I figured it out, but now it has another issue. When you are rotating, and then you stop and rotate the other direction, when you reach a certain point (rotating that direction) the rotation will stop then reverse and start going the other direction even though you are still rotating the same direction. — E. Huckabee

E. Huckabee E. Huckabee · Accepted Answer · 2018-02-08T08:24:35

Here we go, I figured it out after some major changes, info from other SO questions, and a different approach. Using this code you can perfectly rotate a node on any axis (y, in my case) and then "store" its rotation to continue rotating with another pan afterwards.

var previousRotation = SCNVector4(x: 0, y: 0, z: 0, w: 0)

@objc func pan(gesture: UIPanGestureRecognizer) {
    if gesture.numberOfTouches == 2 {
        let view = self.view as! SCNView
        let node = view.scene!.rootNode.childNode(withName: "Node", recursively: false)
        let translate = gesture.translation(in: view)

        var newAngle = Float(translate.x) * Float(Double.pi) / 180.0

        var rotationVector = SCNVector4()
        rotationVector = SCNVector4(x: 0, y: previousRotation.y + Float(translate.y), z: 0, w: previousRotation.w - newAngle)

        switch gesture.state {
        case .began:
            previousRotation = node!.rotation
            break
        case .changed:
            node!.rotation = rotationVector
            break
        default: break
        }
    }
}

Hopefully this helps someone else in the future.

SceneKit: pan gesture not storing previous rotation

1 Answers