如何在 Swift、Sprite 套件中检测碰撞

Question

我一直在用 Swift 编写这个简单的太空游戏，直到遇到检测碰撞的问题。在浏览了论坛、教程等之后，我尝试通过像这样声明位掩码来实现冲突：

对象 1

    enemy?.physicsBody = SKPhysicsBody(circleOfRadius: ((enemy?.size.width)!/2))
    enemy?.physicsBody?.categoryBitMask = enemyBitMask
    enemy?.physicsBody?.contactTestBitMask = bulletBitMask
    enemy?.physicsBody?.collisionBitMask = 0

对象 2

    bullet?.physicsBody? = SKPhysicsBody(rectangleOf: (bullet?.size)!)
    bullet?.physicsBody?.categoryBitMask =  bulletBitMask
    bullet?.physicsBody?.contactTestBitMask =  enemyBitMask
    bullet?.physicsBody?.collisionBitMask = 0
    bullet?.physicsBody?.usesPreciseCollisionDetection = true

我还在

中放了一个打印语句

func didBegin(_ contact: SKPhysicsContact) { print("Hello") }

这是我如何配置我的精灵：

    func CreateNewEnemy() {
    var enemy : SKSpriteNode?

       let moveEnemyDown = SKAction.repeatForever(SKAction.moveBy(x: 0, y: -1, duration: 0.01))
       let rotateEnemy = SKAction.repeatForever(SKAction.rotate(byAngle: 25, duration: 5))

      let enemyXpos = randomNum(high:  self.frame.size.width/2, low: -1 * self.frame.size.width/2)
      let enemyYpos = randomNum(high:  2.5*self.frame.size.height, low: self.frame.size.height/2)
      let enemyOrigin : CGPoint = CGPoint(x: enemyXpos, y: enemyYpos)

      enemy = SKSpriteNode(imageNamed: possibleEnemyImage[Int(arc4random_uniform(4))])
      print(enemy?.size.height)
      enemy?.scale(to: CGSize(width: player.size.height, height: player.size.height))
      print(enemy?.size.height)
      enemy?.position = enemyOrigin
      enemy?.run(moveEnemyDown)
      enemy?.run(rotateEnemy)
      let enemyRadius : CGFloat = (enemy?.size.width)!/2
      print(enemyRadius)

      enemy?.physicsBody? = SKPhysicsBody(circleOfRadius: enemyRadius)

      enemy?.physicsBody?.categoryBitMask = enemyCategory
      enemy?.physicsBody?.contactTestBitMask = bulletCategory
      enemy?.physicsBody?.collisionBitMask = 0
      enemy?.zPosition = 1

      enemiesArray.append(enemy!)
      self.addChild(enemy!)
}

创建敌人（在确实移动到视图函数中调用）

    func CreateAllEnemies(amountOfEnemies : UInt8) {
    for _ in 0...amountOfEnemies {
        CreateNewEnemy()
    }
}

和另一个精灵

    func CreateNewBullet() {
     let bulletOrigin : CGPoint = CGPoint(x: player.position.x, y: player.position.y+player.size.height/2)
     let moveBulletUp = SKAction.repeatForever(SKAction.moveBy(x: 0, y: 3, duration: 0.01))

     var bullet : SKSpriteNode?
     bullet = SKSpriteNode(imageNamed: "bulletImage")
     bullet?.position = bulletOrigin
     bullet?.run(moveBulletUp)

     bullet?.physicsBody? = SKPhysicsBody(rectangleOf: (bullet?.size)!)
     bullet?.physicsBody?.categoryBitMask =  bulletCategory
     bullet?.physicsBody?.contactTestBitMask = enemyCategory
     bullet?.physicsBody?.collisionBitMask = 0
     bullet?.physicsBody?.isDynamic = true
     bullet?.physicsBody?.usesPreciseCollisionDetection = true
     bullet?.zPosition = 1

     bulletsArray.append(bullet!)
     self.addChild(bullet!)
}

这个是用计时器创建的

bulletTimer = Timer.scheduledTimer(timeInterval: 0.25, target: self, selector: #selector(CreateNewBullet) , userInfo: nil, repeats: true)

不幸的是，在我看到两个对象接触后，它没有在控制台中打印任何内容。

Answer 1

1. 定义独特的类别，确保您的班级是SKPhysicsContactDelegate，并让自己成为物理联系人代表：

//Physics categories

let enemyCategory:    UInt32 = 1 << 1
let bulletCategory:   UInt32 = 1 << 2

class GameScene: SKScene, SKPhysicsContactDelegate {
   physicsWorld.contactDelegate = self

1. 分配类别（通常在didMove(to view:)：

   enemy.physicsBody.catgeoryBitMask = enemyCategory bullet.physicsBody.catgeoryBitMask = bulletCategory

（确保您已为每个节点创建物理实体）

1. 设置碰撞：

enemy.physicsBody?.collisionBitMask = 0 // enemy collides with nothing bullet.physicsBody?.collisionBitMask = 0 // bullet collides with nothing

甚至：

for node in [enemy, bullet] {
   node.physicsBody?.collisionBitMask = 0 //  collides with nothing
   }

4. 设置联系人

   bullet.physicsBody?.collisionBitMask = enemyCategory // bullet contacts enemy

确保每个潜在接触中涉及的至少一个对象的物理体上的isDynamic 属性设置为true，否则将不会生成任何接触。两个对象都不必是动态的。

你现在应该在子弹和敌人接触时调用didBegin。你可以像这样编码didBegin：

  func didBegin(_ contact: SKPhysicsContact) {
     print("didBeginContact entered for \(String(describing: contact.bodyA.node!.name)) and \(String(describing: contact.bodyB.node!.name))")

     let contactMask = contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask

     switch contactMask {
     case bulletCategory | enemyCategory:
        print("bullet and enemy have contacted.")
        let bulletNode = contact.bodyA.categoryBitMask == bulletCategory ? contact.bodyA.node : contact.bodyB.node
        enemyHealth -= 10
        bulletNode.removeFromParent
     default:
        print("Some other contact occurred")
     }

}