spritekit physics collision not be detected

Question

I have 4 physics bodies that are all detecting collisions well. However, there is two physics bodies that will not detect when they collide with each other. They do detect when they collide with other physics bodies though. I have contacttestbitmasks for all the them so I do not understand why there is a problem. Here is some code: Here is where I setup my physics bodies:

    struct PhysicsCategory{
    static let None     : UInt32 = 0
    static let All      : UInt32 = UInt32.max
    static let player   : UInt32 = 0b1
    static let bounce   : UInt32 = 0b10
    static let blueball : UInt32 = 0b100
    static let redball  : UInt32 = 0b1000
    static let coin     : UInt32 = 0b10000
}

Here is the code where I used for setting up the player physics body which is one of the problem physic bodies:

     player.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: player.size.width-40, height: player.size.height-40))
    player.physicsBody?.isDynamic = true
    player.physicsBody?.categoryBitMask = PhysicsCategory.player
    player.physicsBody?.contactTestBitMask = PhysicsCategory.blueball
    player.physicsBody?.contactTestBitMask = PhysicsCategory.redball
    player.physicsBody?.collisionBitMask = PhysicsCategory.None

Here is the func for detecting collisions:

  func didBegin(_ contact: SKPhysicsContact) {

    var firstBody: SKPhysicsBody
    var secondBody: SKPhysicsBody
    if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
        firstBody = contact.bodyA
        secondBody = contact.bodyB
    } else {
        firstBody = contact.bodyB
        secondBody = contact.bodyA
    }
    if ((firstBody.categoryBitMask & PhysicsCategory.player != 0) &&
        (secondBody.categoryBitMask & PhysicsCategory.redball != 0)) {
        RedballDidCollideWithPlayer(player: firstBody.node as! SKSpriteNode, redball:  secondBody.node as! SKSpriteNode)
    }
    if ((firstBody.categoryBitMask & PhysicsCategory.player != 0) &&
        (secondBody.categoryBitMask & PhysicsCategory.blueball != 0)) {
        BlueballDidCollideWithPlayer(player: firstBody.node as! SKSpriteNode, blueball:  secondBody.node as! SKSpriteNode)
    }
    if ((firstBody.categoryBitMask & PhysicsCategory.bounce != 0) &&
        (secondBody.categoryBitMask & PhysicsCategory.redball != 0)){
        RedballDidCollideWithBounce(bounce: firstBody.node as! SKSpriteNode, redball: secondBody.node as! SKSpriteNode)
    }
    if ((firstBody.categoryBitMask & PhysicsCategory.bounce != 0) &&
        (secondBody.categoryBitMask & PhysicsCategory.blueball != 0)) {
        BlueballDidCollideWithBounce(bounce: firstBody.node as! SKSpriteNode, blueball: secondBody.node as! SKSpriteNode)
    }
    if ((firstBody.categoryBitMask & PhysicsCategory.bounce != 0) &&
        (secondBody.categoryBitMask & PhysicsCategory.coin != 0)) {
        coinDidCollideWithplayer(player: firstBody.node as! SKSpriteNode, coin: secondBody.node as! SKSpriteNode)
    }
    if ((firstBody.categoryBitMask & PhysicsCategory.player != 0) &&
        (secondBody.categoryBitMask & PhysicsCategory.coin != 0)) {
        coinDidCollideWithplayer(player: firstBody.node as!        SKSpriteNode, coin: secondBody.node as! SKSpriteNode)
    }

}

Here is the code I used for setting up the blueball. This is the other physics body having problems:

    let blueball = SKSpriteNode(imageNamed: "blueball")
        blueball.position = enemyb.position
        blueball.physicsBody = SKPhysicsBody(circleOfRadius: blueball.size.width/2)
        blueball.physicsBody?.isDynamic = true
        blueball.physicsBody?.categoryBitMask = PhysicsCategory.blueball
        blueball.physicsBody?.contactTestBitMask = PhysicsCategory.player
        blueball.physicsBody?.contactTestBitMask = PhysicsCategory.bounce
        blueball.physicsBody?.collisionBitMask = PhysicsCategory.None
        blueball.physicsBody?.usesPreciseCollisionDetection = true
        addChild(blueball)
        let actionMove = SKAction.move(to: player.position, duration: 2)

Any ideas here would be helpful. I have been trying to find the problem for a few days with no luck.

Comment this line of your code and try it again, ` player.physicsBody?.isDynamic = true` — Mina
comment it for both nodes, player and blueball, i think the problem is because of isDynamic property. — Mina

Ali Beadle Ali Beadle · Accepted Answer · 2017-02-05T07:02:53

When setting multiple categories you have to OR the values together. Your code

player.physicsBody?.contactTestBitMask = PhysicsCategory.blueball
player.physicsBody?.contactTestBitMask = PhysicsCategory.redball

Just sets the category twice, the second one overwriting the first. Change this to:

player.physicsBody?.contactTestBitMask = PhysicsCategory.blueball | PhysicsCategory.redball

spritekit physics collision not be detected

1 Answers