SpriteKit comes with a modified version of the Box2D physics framework, and it's wrapped up a lot of complicated physics mathematics into just one or two lines of code. For example, we can create a square, red sprite and give it rectangular physics like this:
let box = SKSpriteNode(color: UIColor.red, size: CGSize(width: 64, height: 64)) box.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: 64, height: 64))
That rectangle will wrap perfectly around the box's color, so it will bounce and rotate as it collides with other objects in your scene.
If you want to create circular physics to simulate balls, this is done using the
let ball = SKSpriteNode(imageNamed: "ballRed") ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.size.width / 2.0)
Available from iOS 7.0 – see Hacking with Swift tutorial 11
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