Camera follow falling ball - swift

Question

I am trying to implement a scene which consists of a ball falling from a height and bouncing off the floor, i would also like the camera to follow the ball throughout its journey. Bellow is an attempt however the ball does not seem to be affected by gravity as println near the bottom of the code always outputs 100. however in reality the ball is on screen for a brief moment quickly falls off screen. What have i done wrong?
class obj {
var sn_node: SCNNode
init() {
let geom = SCNSphere(radius: 2.0)
sn_node = SCNNode(geometry: geom)
sn_node.position = SCNVector3Make(0, 100, 0)
sn_node.physicsBody = SCNPhysicsBody.dynamicBody()
}
}
var obj = obj()
class SceneKitController: NSViewController,SCNSceneRendererDelegate {
var _scene:SCNScene!
var _cameraNode:SCNNode!
var _floorNode:SCNNode!
override func viewDidLoad() {
super.viewDidLoad()
setup()
}
func setup() {
let sceneView = view as SCNView
sceneView.backgroundColor = NSColor.blackColor()
setupScene()
sceneView.scene = _scene
sceneView.delegate = self
sceneView.jitteringEnabled = true
sceneView.autoenablesDefaultLighting = true
var newPos = obj.sn_node.position
newPos.z += 10
_cameraNode.position = newPos
sceneView.pointOfView = _cameraNode
}
func setupScene() {
_scene = SCNScene()
setupEnviroment()
setupSceneElements()
setupInitial()
}
func setupEnviroment() {
//create main camera
let camera = SCNCamera()
_cameraNode = SCNNode()
_cameraNode.camera = camera
//floor
var floor = SCNFloor()
floor.reflectivity = 0;
_floorNode = SCNNode(geometry: floor)
_floorNode.physicsBody = SCNPhysicsBody.staticBody()
_scene.rootNode.addChildNode(_floorNode)
}
func setupSceneElements() {
}
func setupInitial() {
_scene.rootNode.addChildNode(obj.sn_node)
}
func renderer(aRenderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: NSTimeInterval){
var newPos = obj.sn_node.position
println(newPos.y)
}
}

Answer 1

obj.sn_node.presentatioNode.position will give you what you want.