Child nodes inside SKNode disappears with fast shaking device with CMMotionManager applied to move balls - swift

Question

I've create a SKNode with physicsBody edgeFromLoop circular inside which i've added 8 small circular nodes. and 8 circular nodes are moving with CMMotionManager inside Parent circular node. with fast motion shake some balls disappears from screen. SKScene Class given below
Balls only disappears when anyone shake mobile hard randomly.
There are 8 balls initially but after some hard shake reduced.
class GameScene: SKScene {
let motionManager = CMMotionManager()
var Circle = SKShapeNode(circleOfRadius: 108)
var sound = SKAction.playSoundFileNamed(getRandomSound(), waitForCompletion: false)
var collisionBitmasks: [UInt32] = [UInt32]()
override func didMove(to view: SKView) {
Circle.fillTexture = SKTexture.init(image: UIImage.init(named: "img_Ball") ?? UIImage())
Circle.position = CGPoint.init(x: 0, y: 0)
Circle.name = "defaultCircle"
Circle.lineWidth = 0.0
Circle.fillColor = SKColor.lightGray.withAlphaComponent(0.8)
Circle.physicsBody = SKPhysicsBody.init(edgeLoopFrom: UIBezierPath.init(ovalIn: CGRect.init(x: Circle.frame.minX + 12,
y: Circle.frame.minY + 12,
width: Circle.frame.width - 24,
height: Circle.frame.height - 24)).cgPath)
Circle.physicsBody?.isDynamic = true
Circle.physicsBody?.affectedByGravity = false
Circle.physicsBody?.allowsRotation = false
addChild(Circle)
self.physicsWorld.contactDelegate = self
startAcceleroMeter()
for index in 1...8 {
addBalls(index)
}
}
func stop() {
motionManager.stopAccelerometerUpdates()
Circle.children.forEach { (ball) in
ball.physicsBody?.isDynamic = false
ball.physicsBody?.affectedByGravity = false
}
}
func startAcceleroMeter() {
Circle.children.forEach { (ball) in
ball.physicsBody?.isDynamic = true
ball.physicsBody?.affectedByGravity = true
}
motionManager.startAccelerometerUpdates()
motionManager.accelerometerUpdateInterval = 0.1
motionManager.startAccelerometerUpdates(to: .main) { (motionData, error) in
let gravity = CGVector.init(dx: (motionData?.acceleration.x ?? 0.0) * 20, dy: (motionData?.acceleration.y ?? 0.0) * 20)
print(gravity)
self.physicsWorld.gravity = gravity
}
}
func stopPlaying() -> [String] {
var dictionary = [String]()
for (_, ball) in (Circle.children).enumerated() {
dictionary.append("\(ball.position.x), \(ball.position.y), 0.0")
}
return dictionary
}
func addBalls(_ ballNo: Int) {
let ball = SKShapeNode.init(circleOfRadius: 12)
ball.name = "ball\(ballNo)"
ball.fillTexture = SKTexture.init(linearGradientWithAngle: CGFloat.pi, colors: [BallColors(rawValue: ballNo)?.toUIColor(false) ?? UIColor(), BallColors(rawValue: ballNo)?.toUIColor(true) ?? UIColor()], locations: [0, 1], size: ball.frame.size)
ball.fillColor = UIColor.white
ball.physicsBody = SKPhysicsBody.init(circleOfRadius: 12)
ball.physicsBody?.isDynamic = true
ball.physicsBody?.affectedByGravity = true
ball.physicsBody?.allowsRotation = true
ball.physicsBody?.friction = 0.2
ball.physicsBody?.restitution = 0.9
ball.physicsBody?.linearDamping = 0.1
ball.physicsBody?.angularDamping = 0.1
ball.physicsBody?.mass = 0.349065870046616
ball.physicsBody?.usesPreciseCollisionDetection = true
ball.position = CGPoint(x: Circle.frame.midX - CGFloat(ballNo), y: Circle.frame.midY - CGFloat(ballNo))
ball.physicsBody?.fieldBitMask = 1
ball.physicsBody?.categoryBitMask = UInt32.init(ballNo + 100)
let collisionBitMask = UInt32.init(ballNo + 20) | UInt32.init(ballNo + 100)
collisionBitmasks.append(collisionBitMask)
ball.physicsBody?.collisionBitMask = collisionBitMask //To be different for each
ball.physicsBody?.contactTestBitMask = UInt32.init(ballNo + 20)
Circle.addChild(ball)
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
}
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
}
}
extension GameScene: SKPhysicsContactDelegate {
func didBegin(_ contact: SKPhysicsContact) {
if collisionBitmasks.contains(contact.bodyA.collisionBitMask) && collisionBitmasks.contains(contact.bodyB.collisionBitMask) {
run(sound)
}
}
}

Answer 1

You need a hidden magic here. Each small ball adds a constraint that can prevent any accident from high speeds:
ball.constraints = [SKConstraint.distance(SKRange(upperLimit: 108 - 12), to: Circle)]