How to make an sprite bounce within an object? - swift

Question

I am trying to make a ball bounce within a circle so it cant get out of the circumference of the circle. Now the ball bounce in self.frame. How can I make the ball bounce within the circle?
let sceneBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
sceneBody.friction = 0
self.physicsBody = sceneBody
var ball = SKShapeNode(circleOfRadius: 9)
ball.fillColor = SKColor.whiteColor()
ball.position = view.center
ball.physicsBody = SKPhysicsBody(circleOfRadius: 9)
ball.physicsBody?.affectedByGravity = true
ball.physicsBody?.restitution = 1
ball.physicsBody?.linearDamping = 0
ball.zPosition = 3
self.addChild(ball)
circulo = SKSpriteNode(imageNamed: "circuloFondo2")
//Circle that I want the ball bounce within
circulo.size = CGSize(width:view.frame.size.width - padding , height: view.frame.size.width - padding)
circulo.color = UIColor(red: 0.15, green: 0.15, blue: 0.15, alpha: 1)
circulo.colorBlendFactor = 1
circulo.alpha = 0.35
circulo.position = view.center
self.addChild(circulo)
circulo.zPosition = 1

Answer 1

I've prepared a simple test project to explain how to do it:
import UIKit
import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
enum CollisionTypes: UInt32 {
case Circle = 1
case Ball = 2
//case Enemy1 = 4
//case Enemy2 = 8
//case Enemy3 = 16
//case EnemyBoss = 32
}
var circulo: SKSpriteNode!
var padding: CGFloat = 40.0
var center: CGPoint!
override func didMoveToView(view: SKView) {
self.physicsWorld.gravity = CGVectorMake(0, -6)
self.physicsWorld.contactDelegate = self
self.center = CGPointMake(CGRectGetMidX(self.frame),CGRectGetMidY(self.frame))
// Prepare circle
circulo = SKSpriteNode(imageNamed: "circuloFondo2.png")
//Circle that I want the ball bounce within
circulo.size = CGSize(width:view.frame.size.width - padding , height: view.frame.size.width - padding)
let circlePath = UIBezierPath(arcCenter: self.center, radius: (view.frame.size.width - padding*2)/2, startAngle: CGFloat(0), endAngle:CGFloat(M_PI * 2), clockwise: true)
circulo.color = UIColor(red: 0.15, green: 0.15, blue: 0.15, alpha: 1)
circulo.colorBlendFactor = 1
circulo.alpha = 1
circulo.position = self.center
circulo.zPosition = 1
// Set physics
let circuloBody = SKPhysicsBody.init(edgeLoopFromPath: circlePath.CGPath)
self.physicsBody = circuloBody
self.physicsBody!.affectedByGravity = false
self.physicsBody!.usesPreciseCollisionDetection = true
self.physicsBody!.dynamic = true
self.physicsBody!.mass = 0
self.physicsBody!.friction = 0
self.physicsBody!.linearDamping = 0
self.physicsBody!.angularDamping = 0
self.physicsBody!.restitution = 1
self.physicsBody!.categoryBitMask = CollisionTypes.Circle.rawValue
self.physicsBody!.contactTestBitMask = CollisionTypes.Ball.rawValue
//self.circulo.physicsBody!.collisionBitMask = 0
self.addChild(circulo)
//Prepare ball
let ball = SKShapeNode(circleOfRadius: 9)
ball.fillColor = SKColor.whiteColor()
ball.position = self.center
ball.zPosition = 1
// Set physics
ball.physicsBody = SKPhysicsBody(circleOfRadius: 9)
ball.physicsBody!.affectedByGravity = true
ball.physicsBody!.restitution = 0.8
ball.physicsBody!.linearDamping = 0
ball.physicsBody!.friction = 0.3
ball.physicsBody?.dynamic = true
ball.physicsBody!.mass = 0.5
ball.physicsBody!.allowsRotation = true
ball.physicsBody!.categoryBitMask = CollisionTypes.Ball.rawValue
ball.physicsBody!.contactTestBitMask = CollisionTypes.Circle.rawValue
//ball.physicsBody!.collisionBitMask = 0
self.addChild(ball)
}
func didBeginContact(contact: SKPhysicsContact) {
// elements
if (contact.bodyA.categoryBitMask == CollisionTypes.Circle.rawValue &&
contact.bodyB.categoryBitMask == CollisionTypes.Ball.rawValue) {
print("contact between circle and ball")
}
}
The circuloFondo2 image:
A demo about the project:
In this answer you can see all the code to do it, but if you want you can download the project here