Building my first game in XCODE 7(swift 2)-CGPOINTMAKE? - ios

Question

I want to build a game similar to snooker, and at the beginning I already have some problems. I want to build four walls first (that will be the size of the screen-self.frame), and the first one I made like this:
let ground = SKNode()
ground.position = CGPointMake ( 0, 0)
ground.physicsBody = SKPhysicsBody( rectangleOfSize:CGSizeMake(self.frame.size.width * 3, 1))
ground.physicsBody!.dynamic = false
self.addChild(ground)
However, I don't known how to manipulate the values of CGPointMake to do the left/right/up walls. I first imagined that the (0,0) point was the left down corner, but it seems to not be like that. Can someone please help me with this or just explain how this works? (since in https://developer.apple.com/library/prerelease/ios/documentation/GraphicsImaging/Reference/CGGeometry/index.html#//apple_ref/c/func/CGPointMake they dont explain very much =/)

Answer 1

Here is a basic example of how you can restrict the ball from leaving the screen:
import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
let BallCategory : UInt32 = 0x1 << 1
let WallCategory : UInt32 = 0x1 << 2
let ball = SKShapeNode(circleOfRadius: 40)
override func didMoveToView(view: SKView) {
/* Setup your scene here */
physicsWorld.contactDelegate = self
setupWalls()
setupBall()
}
func setupWalls(){
physicsBody = SKPhysicsBody(edgeLoopFromRect: frame)
physicsBody?.categoryBitMask = WallCategory
physicsBody?.contactTestBitMask = BallCategory
physicsBody?.collisionBitMask = BallCategory
}
func setupBall(){
ball.physicsBody = SKPhysicsBody(circleOfRadius: 40)
ball.fillColor = SKColor.whiteColor()
ball.name = "ball"
ball.physicsBody?.categoryBitMask = BallCategory
ball.physicsBody?.contactTestBitMask = WallCategory
ball.physicsBody?.collisionBitMask = WallCategory
ball.physicsBody?.dynamic = true //In order to detect contact between two bodies, at least on body has to be dynamic
ball.physicsBody?.affectedByGravity = false
ball.physicsBody?.restitution = 0.5
ball.position = CGPoint(x: CGRectGetMidX(frame), y: CGRectGetMidY(frame)) // placing to ball in the middle of the screen
addChild(ball)
}
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
ball.physicsBody?.applyImpulse(CGVector(dx: 200, dy: 200))
}
override func update(currentTime: CFTimeInterval) {
/* Called before each frame is rendered */
}
}

Answer 2

Try this for adding four walls with a thickness of twenty:
// Create walls
let leftWall = SKShapeNode(rect: CGRect(x: 0, y: 0, width: 20, height: self.frame.height))
leftWall.fillColor = UIColor.whiteColor()
let physicsBodyLW = SKPhysicsBody(rectangleOfSize: CGSize(width: 20, height: self.frame.size.height), center: CGPoint(x:10, y:self.frame.height/2))
physicsBodyLW.affectedByGravity = false
physicsBodyLW.dynamic = false
leftWall.physicsBody = physicsBodyLW
self.addChild(leftWall)
let rightWall = SKShapeNode(rect: CGRect(x: self.frame.width - 20, y: 0, width: 20, height: self.frame.height))
rightWall.fillColor = UIColor.whiteColor()
let physicsBodyRW = SKPhysicsBody(rectangleOfSize: CGSize(width: 20, height: self.frame.size.height), center: CGPoint(x:10, y:self.frame.height/2))
physicsBodyRW.affectedByGravity = false
physicsBodyRW.dynamic = false
rightWall.physicsBody = physicsBodyRW
self.addChild(rightWall)
let topWall = SKShapeNode(rect: CGRect(x: 0, y: self.frame.height-20, width: self.frame.width, height: 20))
topWall.fillColor = UIColor.whiteColor()
let physicsBodyTW = SKPhysicsBody(rectangleOfSize: CGSize(width: self.frame.size.width, height: 20), center: CGPoint(x:self.frame.width/2, y:10))
physicsBodyTW.affectedByGravity = false
physicsBodyTW.dynamic = false
topWall.physicsBody = physicsBodyTW
self.addChild(topWall)
let bottomWall = SKShapeNode(rect: CGRect(x: 0, y: 0, width: self.frame.width, height: 20))
print(bottomWall.frame)
bottomWall.fillColor = UIColor.whiteColor()
let physicsBodyBW = SKPhysicsBody(rectangleOfSize: CGSize(width: self.frame.size.width, height: 20), center: CGPoint(x:self.frame.width/2, y:10))
physicsBodyBW.affectedByGravity = false
physicsBodyBW.dynamic = false
bottomWall.physicsBody = physicsBodyBW
self.addChild(bottomWall)