碰撞检测不能完全工作

Question

import SpriteKit
import GameplayKit

class GameScene: SKScene, SKPhysicsContactDelegate {
    let balls = [
    SKSpriteNode(imageNamed: "blueball.png"),
    SKSpriteNode(imageNamed: "greenball.png"),
    SKSpriteNode(imageNamed: "realredball.png"),
    ]
let redRectangle = SKSpriteNode(imageNamed: "redrectangle.png")
let blueRectangle = SKSpriteNode(imageNamed: "bluerectangle.png")
let greenRectangle = SKSpriteNode(imageNamed: "greenrectangle.png")

let blueBallCategory :UInt32 = 0x1 << 0
let greenBallCategory :UInt32 = 0x1 << 1
let realRedBallCategory :UInt32 = 0x1 << 2
let redRectangleCategory : UInt32 = 0x1 << 3
let blueRectangleCategory : UInt32 = 0x1 << 4
let greenRectangleCategory : UInt32 = 0x1 << 5

override func didMove(to view: SKView) {
    spawnBallsandRectangles()
    physicsWorld.contactDelegate = self
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    physics()
}
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 == blueBallCategory && secondBody.categoryBitMask == blueRectangleCategory {
        print("alive")
        }
    else if firstBody.categoryBitMask == greenBallCategory && secondBody.categoryBitMask == greenRectangleCategory {
        print("alive")
    }
    else if firstBody.categoryBitMask == realRedBallCategory && secondBody.categoryBitMask == redRectangleCategory {
        print("alive")
    }
    else if firstBody.categoryBitMask == blueBallCategory || firstBody.categoryBitMask == greenBallCategory && secondBody.categoryBitMask == redRectangleCategory{
        print("dead")
    }
    else if firstBody.categoryBitMask == realRedBallCategory || firstBody.categoryBitMask == greenBallCategory && secondBody.categoryBitMask == blueRectangleCategory {
        print("dead")
    }
    else if firstBody.categoryBitMask == realRedBallCategory || firstBody.categoryBitMask == blueBallCategory && secondBody.categoryBitMask == greenBallCategory {
    print("dead")
        }
    }


func spawnBallsandRectangles() {
    let ball = balls[Int(arc4random_uniform(UInt32(balls.count)))]
    ball.position = CGPoint(x: -200, y: 250)
    ball.size = CGSize(width: 70, height: 70)
    redRectangle.position = CGPoint(x: 0, y: -600)
    redRectangle.size = CGSize(width: 200, height: 20)
    blueRectangle.position = CGPoint(x: -200, y: -600)
    blueRectangle.size = CGSize(width: 200, height: 20)
    greenRectangle.position = CGPoint(x: 200, y: -600)
    greenRectangle.size = CGSize(width: 200, height: 20)
    self.addChild(ball)
    self.addChild(redRectangle)
    self.addChild(blueRectangle)
    self.addChild(greenRectangle)

}
func physics(){
    for ball in balls{
        ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.size.height/2)
               }
    redRectangle.physicsBody = SKPhysicsBody(rectangleOf: redRectangle.size)
    redRectangle.physicsBody?.affectedByGravity = false
    redRectangle.physicsBody?.isDynamic = false
    blueRectangle.physicsBody = SKPhysicsBody(rectangleOf: redRectangle.size)
    blueRectangle.physicsBody?.affectedByGravity = false
    blueRectangle.physicsBody?.isDynamic = false
    greenRectangle.physicsBody = SKPhysicsBody(rectangleOf: redRectangle.size)
    greenRectangle.physicsBody?.isDynamic = false
    greenRectangle.physicsBody?.affectedByGravity = false
    balls[0].physicsBody?.categoryBitMask = blueBallCategory
    balls[1].physicsBody?.categoryBitMask = greenBallCategory
    balls[2].physicsBody?.categoryBitMask = realRedBallCategory
    balls[0].physicsBody?.contactTestBitMask = redRectangleCategory
    balls[1].physicsBody?.contactTestBitMask = redRectangleCategory
    balls[1].physicsBody?.contactTestBitMask = blueRectangleCategory
    balls[2].physicsBody?.contactTestBitMask = blueRectangleCategory
    balls[0].physicsBody?.contactTestBitMask = greenRectangleCategory
    balls[2].physicsBody?.contactTestBitMask = greenRectangleCategory
    balls[0].physicsBody?.contactTestBitMask = blueRectangleCategory
    balls[1].physicsBody?.contactTestBitMask = greenRectangleCategory
    balls[2].physicsBody?.contactTestBitMask = redRectangleCategory
    redRectangle.physicsBody?.categoryBitMask = redRectangleCategory
    blueRectangle.physicsBody?.categoryBitMask = blueRectangleCategory
    greenRectangle.physicsBody?.categoryBitMask = greenRectangleCategory


}
}

我已经设置了碰撞检测，这样如果一个球碰撞到一个匹配颜色的矩形，程序就会打印（“alive”）。如果颜色不匹配，程序应该打印（“死”）。如果颜色匹配并打印（“alive”）但不打印（“dead”），它会检测到碰撞。有人可以帮忙吗，谢谢。

Answer 1

您可能会发现像这样构建您的 didBegin() 可能有助于摆脱所有这些 else ifs：

func didBegin(_ contact: SKPhysicsContact) {

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

    switch contactMask {

    case blueBallCategory | blueRectangleCategory:
       print("Alive! Blue ball has hit blue rectangle.")

    case greenBallCategory | greenRectangleCategory:
       print("Alive! Green ball has hit green rectangle.")

    case redBallCategory | redRectangleCategory:
       print("Alive! Red ball has hit red rectangle.")

    default :
        print("Dead! Some other contact has occurred")
    }
}

如果一个球碰到一个不同颜色的矩形，你想发生什么？

编辑：

来自physics() 函数中的这段代码：

balls[0].physicsBody?.contactTestBitMask = redRectangleCategory
balls[1].physicsBody?.contactTestBitMask = redRectangleCategory
balls[1].physicsBody?.contactTestBitMask = blueRectangleCategory
balls[2].physicsBody?.contactTestBitMask = blueRectangleCategory
balls[0].physicsBody?.contactTestBitMask = greenRectangleCategory
balls[2].physicsBody?.contactTestBitMask = greenRectangleCategory
balls[0].physicsBody?.contactTestBitMask = blueRectangleCategory
balls[1].physicsBody?.contactTestBitMask = greenRectangleCategory
balls[2].physicsBody?.contactTestBitMask = redRectangleCategory

每次您为特定物理体的 contactTestbitMask 分配一个新值时，您是在覆盖之前的值，而不是添加到它。因此，唯一重要的行是：

balls[0].physicsBody?.contactTestBitMask = blueRectangleCategory
balls[1].physicsBody?.contactTestBitMask = greenRectangleCategory
balls[2].physicsBody?.contactTestBitMask = redRectangleCategory

所以balls[0]（蓝色球）只接触蓝色矩形，balls[1]（绿色球）只接触绿色矩形，balls[2]（真正的红色球）只接触红色矩形。所以didBegin() 不会被调用，如果一个球接触到一个不同颜色的矩形，这就是为什么你永远看不到你的“死”消息。

另一个编辑：

如果您希望所有球在接触任何矩形时触发 didBegin()，那么您的球的 contactTestBitMasks 应包括所有矩形：

for ball in balls {
    balls.physicsBody?.contactTestBitMask = blueRectangleCategory | greenRectangleCategory | redRectangleCategory
}

或者如果球已经定义了一些接触并且您只想将矩形添加到它们的碰撞位掩码中：

for ball in balls {
    balls.physicsBody?.contactTestBitMask |= (blueRectangleCategory | greenRectangleCategory | redRectangleCategory)
}