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我做了一个游戏，它基本上有一个球、几个目标和桨。但是，我需要根据球与哪个目标相撞，只要它不低于最小速度或不超过最大速度，速度就会增加三倍、两倍或减半。

为此，我一起使用了 didBegin(contact) 函数并设置了不同的速度，如下面的代码所示：

extension CGVector {
var speed: CGFloat {
    return hypot(dx, dy)
}

static func > (lhs: CGVector, rhs: CGVector) -> Bool {
    return lhs.speed > rhs.speed
}

static func < (lhs: CGVector, rhs: CGVector) -> Bool {
    return lhs.speed < rhs.speed
}

static func * (vector: CGVector, multiplier: CGFloat) -> CGVector {
    return CGVector(dx: vector.dx * multiplier, dy: vector.dy * multiplier)
}

static func / (vector:CGVector, divider:CGFloat) -> CGVector {
    return CGVector(dx: vector.dx / divider, dy: vector.dy / divider)
}
}

func didBegin(_ contact: SKPhysicsContact) {
    var firstBody = SKPhysicsBody()
    var secondBody = SKPhysicsBody()
    let ballNode = self.childNode(withName: ballName)
    let minSpeed = self.initialSpeed / 2
    let maxSpeed = self.initialSpeed * 3

    if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
        firstBody = contact.bodyA
        secondBody = contact.bodyB
    } else {
        firstBody = contact.bodyB
        secondBody = contact.bodyA
    }

    if firstBody.categoryBitMask == ballBitmask && secondBody.categoryBitMask == drainBitmask {
        endGame()
        Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(GameScene.showLeaderboard), userInfo: nil, repeats: false)

    } else if firstBody.categoryBitMask == ballBitmask && secondBody.categoryBitMask == target1Bitmask {
        let currentSpeed = ballNode?.physicsBody?.velocity
        score += 20
        self.vc.scoreLabel.text = "Score: \(score)"

        if currentSpeed == maxSpeed {

            ballNode?.physicsBody?.velocity = currentSpeed!

        } else if (currentSpeed! * 2) > maxSpeed {

            ballNode?.physicsBody?.velocity = maxSpeed

        } else if (currentSpeed! * 2) < maxSpeed {

            ballNode?.physicsBody?.velocity = currentSpeed! * 2

        }

    } else if firstBody.categoryBitMask == ballBitmask && secondBody.categoryBitMask == target2Bitmask {
        let currentSpeed = ballNode?.physicsBody?.velocity
        score += 10
        self.vc.scoreLabel.text = "Score: \(score)"

        if currentSpeed == minSpeed {

            ballNode?.physicsBody?.velocity = currentSpeed!

        } else if (currentSpeed! / 2) > minSpeed {

            ballNode?.physicsBody?.velocity = currentSpeed! / 2

        } else if (currentSpeed! / 2) < minSpeed {

            ballNode?.physicsBody?.velocity = minSpeed

        }


    } else if firstBody.categoryBitMask == ballBitmask && secondBody.categoryBitMask == target3Bitmask {
        let currentSpeed = ballNode?.physicsBody?.velocity
        score += 30
        self.vc.scoreLabel.text = "Score: \(score)"

        if currentSpeed == maxSpeed {

            ballNode?.physicsBody?.velocity = currentSpeed!

        } else if (currentSpeed! * 3) > maxSpeed {

            ballNode?.physicsBody?.velocity = maxSpeed

        } else if (currentSpeed! * 3) < maxSpeed {

            ballNode?.physicsBody?.velocity = currentSpeed! * 3

        }


    }

我的问题是有时当球与目标相撞时，它会以一种非常奇怪和不切实际的方式弹开，有时基本上会出现故障（请查看下面的链接以获取显示我的意思的简短视频剪辑）

注意：在视频 2/3 秒处是一个奇怪的反弹发生的例子

https://drive.google.com/open?id=0BxgQmn_JruJ_aUU2dVBoVlprV0k

为什么会发生这种情况，更重要的是我该如何解决？

PS：我认为可能导致这种情况的一个建议是，速度矢量同时控制了球的角度（方向）和速度（我认为），因此当我设置速度时，没有考虑方向。如果这是原因，是否有可能在使弹跳逼真的同时将速度增加三倍/两倍/减半？

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