Sprites Colliding despite differing bitmasks

Question

I have 5 different category bitmasks for my sprites:

• redBullet (enemy shot)
• greenBullet (playershot)
• shipCategory (player Sprite)
• enemyShipCategory (AI Sprite)
• wallCategory (screen border)

I have set my bitmasks properly, but I am getting some collisions that should not happen. Both bullets will collide with each other and the wall instead of passing through. Why is this happening if those bitmasks aren't included in the collisionBitmap?

let shipCategory: UInt32 = 1
let wallCategory: UInt32 = 2
let greenBulletCategory: UInt32 = 3
let enemyShipCategory: UInt32 = 4
let redBulletCategory: UInt32 = 5

    self.anchorPoint = CGPoint.init(x: 0.5, y: 0.5)
    setUpHeaderUI()
    self.physicsWorld.gravity = CGVector.zero
    self.physicsWorld.contactDelegate = self
    createBG()
    addShip()
    self.physicsBody = SKPhysicsBody.init(edgeLoopFrom: self.frame)
    self.physicsBody?.collisionBitMask = shipCategory | enemyShipCategory
    self.physicsBody?.categoryBitMask = wallCategory
    self.physicsBody?.friction = 0

func enemyShoot(node: SKSpriteNode){
    Bullet = SKSpriteNode.init(imageNamed: "red.svg.hi")
    Bullet.zPosition = 1
    Bullet.setScale(0.2)
    Bullet.position = node.position
    Bullet.physicsBody = SKPhysicsBody.init(rectangleOf: Bullet.size)
    Bullet.physicsBody?.isDynamic = true
    Bullet.physicsBody?.allowsRotation = true
    Bullet.physicsBody?.linearDamping = 0
    Bullet.physicsBody?.friction = 0
    Bullet.physicsBody?.categoryBitMask = redBulletCategory
    Bullet.physicsBody?.contactTestBitMask = shipCategory
    Bullet.physicsBody?.velocity = CGVector.init(dx: ((node.physicsBody?.velocity.dx)!/100), dy: CGFloat.init(-750))
    Bullet.name = "Bullet"
    self.addChild(Bullet)
}

func playerShoot(){
    changePower(change: 10)
    if(power > 99 ){
        consPowerTimer.invalidate()
        changePower(change: 100 - power)
        canFire = false
        powerTimer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.powerCooldown), userInfo: nil, repeats: true)
    }
    else{
    Bullet = SKSpriteNode.init(imageNamed: "green.svg.hi")
    Bullet.zPosition = 1
    Bullet.zRotation = CGFloat.init(3 * Double.pi/2)
    Bullet.setScale(0.2)
    Bullet.position = ship.position
    Bullet.physicsBody = SKPhysicsBody.init(rectangleOf: Bullet.size)
    Bullet.physicsBody?.isDynamic = true
    Bullet.physicsBody?.allowsRotation = true
    Bullet.physicsBody?.linearDamping = 0
    Bullet.physicsBody?.friction = 0
    Bullet.physicsBody?.categoryBitMask = greenBulletCategory
    Bullet.physicsBody?.contactTestBitMask = enemyShipCategory
    print(ship.physicsBody?.velocity.dx)
    Bullet.physicsBody?.velocity = CGVector.init(dx: (ship.physicsBody?.velocity.dx)!, dy: CGFloat.init(750))
    Bullet.name = "Bullet"
    self.addChild(Bullet)
    }

func addAttackShip(){
    //30,40,40
    let enemy = attackShip.init()
    enemy.setScale(0.08)
    enemy.zRotation = CGFloat(0)
    enemy.physicsBody = SKPhysicsBody.init(rectangleOf: enemy.size)
    enemy.physicsBody?.isDynamic = true
    enemy.name = "enemy"
    enemy.zPosition = 2
    enemy.physicsBody?.mass = CGFloat.init(10)
    enemy.physicsBody?.friction = 0
    enemy.physicsBody?.categoryBitMask = enemyShipCategory
    enemy.physicsBody?.collisionBitMask = enemyShipCategory | wallCategory
    enemy.physicsBody?.contactTestBitMask = greenBulletCategory | shipCategory
    enemy.position = CGPoint.init(x: 0, y: 155.504 - enemy.size.height / 2)
    enemy.zRotation = CGFloat(2.4870942)
    let healthindicator = SKSpriteNode.init(color: UIColor.green, size: CGSize.init(width: 150, height: 30))
    healthindicator.name = "healthdisplay"
    healthindicator.zPosition = 3
    healthindicator.zRotation = -1 * CGFloat(2.4870942)
    enemy.addChild(healthindicator)
    addChild(enemy)
}

func addShip() {
    ship = SKSpriteNode(imageNamed: "Spaceship")
    ship.setScale(0.2)
    ship.zRotation = CGFloat(0)
    ship.physicsBody = SKPhysicsBody(rectangleOf: ship.size)
    ship.physicsBody?.isDynamic = true
    ship.name = "ship"
    ship.position = CGPoint.init(x: 0, y: (-(self.frame.size.height/2)) + ship.size.height/2)
    ship.zPosition = 2
    ship.physicsBody?.mass = CGFloat.init(10)
    ship.physicsBody?.friction = 0
    ship.physicsBody?.categoryBitMask = shipCategory
    ship.physicsBody?.collisionBitMask = wallCategory
    ship.physicsBody?.contactTestBitMask = redBulletCategory | enemyShipCategory
    self.addChild(ship)
    if motionManager.isAccelerometerAvailable == true {
        motionManager.startAccelerometerUpdates(to: OperationQueue.current!, withHandler:{
            data, error in
            if (data!.acceleration.y) < -0.05 {
                self.velocity = -500
            }

            else if data!.acceleration.y > 0.05 {
                self.velocity = 500
         }
            else{
                self.velocity = 0
            }

        })

    }
}

Answer 1

Your bullet's physicsBody does is not a collisionBitmask. As such it will assume the default mask of 0xFFFFFFFF and collide with everything. If you don't need it to collide with anything, assign it a collisionMask of 0.