Objects Position Not Matching Up (Spritekit) - swift

Question

I am building a spritekit game and have just started the project. I have a circle on the screen which starts in the center, and when i drag my finger from the circle outward, it will show a dotted line/bezierpath connected to the ball which will help the user see where it is aiming the ball. When the user lifts their finger, the ball will shoot in the opposite direction of the aim line. (Think a game like soccer stars or pool). The issue is that the maneuver works the first time when everything starts in the middle: I drag my finger and the ball shoots in opposite direction then stops. But when I try it again, the position of the aiming line says it is the same as the ball (It should be), but then it shows up like an inch away from the ball on the screen. I feel like this may be an issue that the scene(s) behind the objects may not be the same size? But I'm confused because I think I'm only using one scene.
GameViewController viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
if let view = self.view as! SKView? {
// Load the SKScene from 'GameScene.sks'
if let scene = SKScene(fileNamed: "GameScene") {
// Set the scale mode to scale to fit the window
scene.scaleMode = .aspectFill
scene.size = view.bounds.size
//scene.anchorPoint = CGPoint(x: 0.0, y: 0.0)
// Present the scene
view.presentScene(scene)
}
view.ignoresSiblingOrder = true
view.showsFPS = true
view.showsNodeCount = true
}
}
GameScene Code (Doubt you need all of it but whatever):
import SpriteKit
import GameplayKit
class GameScene: SKScene {
var ball = SKShapeNode(circleOfRadius: 35)
var touchingBall = false
var aimLine = SKShapeNode()
var startAimPoint = CGPoint()
var endAimPoint = CGPoint()
let damping:CGFloat = 0.94
override func didMove(to view: SKView) {
ball.fillColor = SKColor.orange
ball.name = "ball"
let borderBody = SKPhysicsBody(edgeLoopFrom: self.frame)
borderBody.friction = 0
self.physicsBody = borderBody
physicsWorld.gravity = CGVector(dx: 0.0, dy: 0.0)
var physicsBody = SKPhysicsBody(circleOfRadius: 35)
ball.physicsBody = physicsBody
ball.physicsBody?.affectedByGravity = false
ball.physicsBody?.friction = 10.0
ball.position = CGPoint(x: frame.midX, y: frame.midY)
self.addChild(ball)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
print("TOUCHES BEGAN.")
for touch in touches {
print("TB: \(touchingBall)")
let location = touch.location(in: self)
let node : SKNode = self.atPoint(location)
if node.name == "ball" {
// touched inside node
if ball.physicsBody!.angularVelocity <= 0.0{
touchingBall = true
startAimPoint = ball.position
print(touchingBall)
}
}
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
print("TOCUHES MOVED.")
for touch in touches {
let location = touch.location(in: self)
if touchingBall{
endAimPoint = location
assignAimLine(start: startAimPoint, end: endAimPoint)
print("Moving touched ball")
}
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
print("Touches ended. \(touchingBall)")
if touchingBall == true{
ball.physicsBody!.applyImpulse(CGVector(dx: -(endAimPoint.x - startAimPoint.x) * 3, dy: -(endAimPoint.y - startAimPoint.y) * 3))
}
touchingBall = false
aimLine.removeFromParent()
print(touchingBall)
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
print("Touches cancelled. \(touchingBall)")
if touchingBall == true{
ball.physicsBody!.applyImpulse(CGVector(dx: -(endAimPoint.x - startAimPoint.x) * 3, dy: -(endAimPoint.y - startAimPoint.y) * 3))
}
touchingBall = false
aimLine.removeFromParent()
print(touchingBall)
}
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
print(ball.physicsBody!.velocity)
let dx2 = ball.physicsBody!.velocity.dx * damping
let dy2 = ball.physicsBody!.velocity.dy * damping
ball.physicsBody!.velocity = CGVector(dx: dx2, dy: dy2)
}
func assignAimLine(start: CGPoint, end: CGPoint){
aimLine.removeFromParent()
var bezierPath = UIBezierPath()
bezierPath.move(to: start)
bezierPath.addLine(to: shortenedEnd(startPoint: start, endPoint: end))
var pattern : [CGFloat] = [10.0, 10.0]
let dashed = SKShapeNode(path: bezierPath.cgPath.copy(dashingWithPhase: 2, lengths: pattern))
aimLine = dashed
aimLine.position = ball.position
aimLine.zPosition = 0
self.addChild(aimLine)
}
func hypotenuse(bp: UIBezierPath) -> Double{
var a2 = bp.cgPath.boundingBox.height * bp.cgPath.boundingBox.height
var b2 = bp.cgPath.boundingBox.width * bp.cgPath.boundingBox.width
return Double(sqrt(a2 + b2))
}
func hypotenuse(startP: CGPoint, endP: CGPoint) -> Double{
var bezierPath = UIBezierPath()
bezierPath.move(to: startP)
bezierPath.addLine(to: endP)
return hypotenuse(bp: bezierPath)
}
func shortenedEnd(startPoint: CGPoint, endPoint: CGPoint) -> CGPoint{
var endTemp = endPoint
//while hypotenuse(startP: startPoint, endP: endTemp) > 150{
endTemp = CGPoint(x: endTemp.x / 1.01, y: endTemp.y / 1.01)
//}
return endTemp
}
func addTestPoint(loc: CGPoint, color: UIColor){
var temp = SKShapeNode(circleOfRadius: 45)
temp.fillColor = color
temp.position = loc
self.addChild(temp)
}
}
I tried printing the frame size for the scene and it says 400 something x 700 something (I am testing on iPhone 6 Plus), and it says the UIScreen is same size so i don't know what issue is. Overall, I just need the aiming line to be on the center of the circle more than just the first time I try the maneuver. Thanks.

Answer 1

Like I mentioned in the comments, your problem was how you were laying out your paths. The code below makes the path relative to the ball instead of absolute to the scene. I also fixed the issue with creating new shapes every time.
import SpriteKit
import GameplayKit
class GameScene: SKScene {
var ball = SKShapeNode(circleOfRadius: 35)
var touchingBall = false
var aimLine = SKShapeNode()
var endAimPoint = CGPoint()
override func didMove(to view: SKView) {
ball.fillColor = SKColor.orange
ball.name = "ball"
let borderBody = SKPhysicsBody(edgeLoopFrom: self.frame)
borderBody.friction = 0
self.physicsBody = borderBody
physicsWorld.gravity = CGVector(dx: 0.0, dy: 0.0)
ball.position = CGPoint(x: frame.midX, y: frame.midY)
let physicsBody = SKPhysicsBody(circleOfRadius: 35)
physicsBody.affectedByGravity = false
physicsBody.friction = 10.0
physicsBody.linearDamping = 0.94
ball.physicsBody = physicsBody
self.addChild(ball)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
print("TOUCHES BEGAN.")
for touch in touches {
print("TB: \(touchingBall)")
let location = touch.location(in: self)
let node : SKNode = self.atPoint(location)
if node.name == "ball" {
// touched inside node
if ball.physicsBody!.angularVelocity <= 0.0{
touchingBall = true
aimLine.path = nil
self.addChild(aimLine)
print(touchingBall)
}
}
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
print("TOCUHES MOVED.")
for touch in touches {
let location = touch.location(in: self)
if touchingBall{
endAimPoint = self.convert(location, to: ball)
assignAimLine(end: endAimPoint)
print("Moving touched ball")
}
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
print("Touches ended. \(touchingBall)")
if touchingBall == true{
ball.physicsBody!.applyImpulse(CGVector(dx: -(endAimPoint.x) * 3, dy: -(endAimPoint.y) * 3))
}
touchingBall = false
aimLine.removeFromParent()
print(touchingBall)
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
print("Touches cancelled. \(touchingBall)")
if touchingBall == true{
ball.physicsBody!.applyImpulse(CGVector(dx: -(endAimPoint.x) * 3, dy: -(endAimPoint.y) * 3))
}
touchingBall = false
aimLine.removeFromParent()
print(touchingBall)
}
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
print(ball.physicsBody!.velocity)
//let dx2 = ball.physicsBody!.velocity.dx * damping
//let dy2 = ball.physicsBody!.velocity.dy * damping
//ball.physicsBody!.velocity = CGVector(dx: dx2, dy: dy2)
}
func assignAimLine(end: CGPoint){
let bezierPath = UIBezierPath()
bezierPath.move(to: CGPoint.zero)
bezierPath.addLine(to: end)
let pattern : [CGFloat] = [10.0, 10.0]
aimLine.position = ball.position
aimLine.path = bezierPath.cgPath.copy(dashingWithPhase: 2, lengths: pattern)
aimLine.zPosition = 0
}
func addTestPoint(loc: CGPoint, color: UIColor){
var temp = SKShapeNode(circleOfRadius: 45)
temp.fillColor = color
temp.position = loc
self.addChild(temp)
}
}