Locking scene to a sprite node swift xcode - ios

Question

Basically, I want to move the character (player) and have the “camera” or scene follow them in the world. The problem is Apple/xcode does not have a built in camera node and if I try to move the scene, I get an error saying something to the effect of “SKScene cannot be moved.” I don’t want to just move the background around and lock the player in place because I want to be able to apply forces to the player node. I have gone to Apple’s website to the Advanced Scene Processing page and followed the example but it doesn’t work. I just need a nudge in the right direction. Thanks!
Code:
(I have deleted pieces of code that are irrelevant)
class PlayScene: SKScene, SKPhysicsContactDelegate {
let world = SKNode()
let player = SKShapeNode(circleOfRadius: 25)
var cannonRotation = 0.0
var fired = false
override func didMoveToView(view: SKView) {
physicsWorld.contactDelegate = self
self.anchorPoint = CGPoint(x: 0.5, y: 0.5)
self.addChild(world)
//Adds the background to the world
//Adds the elements to the scene
player.fillColor = UIColor.whiteColor()
player.position = CGPoint(x: CGRectGetMidX(self.frame), y: CGRectGetMinY(self.frame)+65+25)
player.zPosition = 2
player.physicsBody = SKPhysicsBody(circleOfRadius: 25)
player.physicsBody?.dynamic = true
player.physicsBody?.restitution = 0.9
player.physicsBody?.categoryBitMask = BodyType.player.rawValue
//Adds the physics properties to GameScene
let physicsGround = SKPhysicsBody(edgeFromPoint: CGPoint(x: CGRectGetMinX(self.frame), y: CGRectGetMinY(self.frame)+65), toPoint: CGPoint(x: CGRectGetMaxX(self.frame), y: CGRectGetMinY(self.frame)+65))
self.physicsBody = physicsGround
}
override func touchesEnded(touches: NSSet, withEvent event: UIEvent) {
powerLevel()
totalPower = powerReached * playCannon.powerMultiplier
self.addChild(player)
player.physicsBody?.applyImpulse(CGVector(dx: CGFloat(Float(totalPower)*cosf(Float(cannonRotation))), dy: CGFloat(Float(totalPower)*sinf(Float(cannonRotation)))))
fired = true
}

Answer 1

Override didsimulatePhysics, And in that function call this
self.centerOnNode(player);
What that does, It calles a function we will later create and it sendes a parameter of an SKNode and in your case it is the player node. Next create a method called centerOnNede and add the following parameters
func centerOnNode(node: SKNode) {
}
In the centerOnNode function add this following line of code.
var cameraPosition: CGPoint = node.scene?.convertPoint(node.position, fromNode: node.parent!)
cameraPosition.x = 0
let posX = node.parent?.position.x
let posY = node.parent?.position.y
node.parent?.position = CGPointMake(posX! - cameraPosition.x, posY! - cameraPosition.y)
That will center the camera on to the node and update it's position. Code converted from here. How to make camera follow SKNode in Sprite Kit?

Answer 2

There is a detailed example of how to do this in the Apple Adventure reference game. It has both Swift and Objective-C examples.
In summary what they recommend is that you
Put all nodes on a background node (SKNode) container.
implement didSimulatePhysics and move the world in the opposite direction of the player. That will keep the player in the middle of the screen. Special logic will be needed if you want the camera to bump into the edge of your world.
A camera node would be very helpful, but has not been implemented into SpriteKit.

Answer 3

As of iOS 9 there is now an SKCameraNode that does all the heavy lifting for you.
Simply add these three lines of code in your didMoveToView function:
let cameraNode = SKCameraNode()
self.addChild(cameraNode)
self.camera = cameraNode
Then in your didFinishUpdate function just set the cameraNode's position to whatever SKSpriteNode you want it to follow.