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swiftsprite-kitframe-ratelagskscene

Fast-paced SpriteKit game has irregular CPU activity and is jittery/lags despite frame rate staying high - Swift

I'm having the issue on a simple but fast-paced SpriteKit game, but I've reduced my code just to a bouncing ball and still get the issue to a lesser extent:

override func didMove(to view: SKView) {
    super.didMove(to: view)

    physicsWorld.contactDelegate = self
    physicsWorld.speed = 1
    physicsWorld.gravity = CGVector(dx: 0.0, dy: 0.0)

    let borderBody = SKPhysicsBody(edgeLoopFrom: self.frame)
    borderBody.friction = 0
    self.physicsBody = borderBody
    borderBody.contactTestBitMask = BallCategory

    addBall()
}

func addBall() {
    let size = CGSize(width: 20, height: 20)
    let position = CGPoint(x: frame.width / 2, y: 50)

    let texture = SKTexture(image: #imageLiteral(resourceName: "whiteCircle"))
    let ball = SKSpriteNode(texture: texture, size: size)
    ball.position = position
    ball.physicsBody = SKPhysicsBody(circleOfRadius: size.width / 2)
    ball.fillColor = .white
    ball.lineWidth = 0
    addStandardProperties(node: ball, name: "ball", z: 5, contactTest: 0, category: BallCategory)
    ball.physicsBody?.isDynamic = true
    addChild(ball)
    launchBall()
}

func addStandardProperties(node: SKNode, name: String, z: CGFloat, contactTest: UInt32, category: UInt32) {

    node.name = name
    node.zPosition = z
    node.physicsBody?.isDynamic = false
    node.physicsBody?.affectedByGravity = false
    node.physicsBody?.mass = 0
    node.physicsBody?.restitution = 1
    node.physicsBody?.friction = 0
    node.physicsBody?.linearDamping = 0
    node.physicsBody?.angularDamping = 0
    node.physicsBody?.angularVelocity = 0
    node.physicsBody?.contactTestBitMask = contactTest
    node.physicsBody?.categoryBitMask = category

}

func launchBall() {
    let ball = childNode(withName: "ball")!
    ball.physicsBody?.velocity = CGVector(dx: 0, dy: 500)
}

This code results in a ball (SKSpriteNode) bouncing up and down. When I run this, CPU usage starts at around 10% on my iPhone 6s and then after increases to around 25-30% after maybe 30-60 seconds (no idea why it's increasing). Throughout all of this, the frame rate stays very close to 60 FPS, usually going no lower than 58 FPS (it's the same way when I run the full game).

Almost any time an alert pops up (e.g., text messages, logging into Game Center, etc.), the lag shows up and shows up at random times when I'm running the full game.

I've also tried deleting and re-running the app, cleaning the project, deleting derived data and running in Release mode. None of these worked permanently.

Should I give up on SpriteKit and try another framework? If so, which? Cocos2D?

Any help is appreciated.

enter image description here

Solution

  • Turns out I had 2 SKViews in my view controller. By default, when you start a project as a SpriteKit game, Xcode sets the view controller root/superview of the GameViewController as an SKView. At some point, I had added a second SKView because I didn't intend for the scene to take up the entire screen and I apparently didn't realize that the VC root view was still set as an SKView. So every time GameViewController loaded, it was loading two SKViews, which is why I saw 120 FPS in Xcode.

    I fixed the issue by simply removing the SKView class designation from the VC root view.

    enter image description here