Sprite kit 慢化SKEmitterNode的粒子

我只是好奇，有没有办法减缓粒子沿场景中其他对象的发射。假设您有一个粒子发射器和一个精灵。使用

SKAction

移动精灵。发射器正在发射。这两个节点都将添加到场景中。如果将

self.speed

设置为0.5，则只有精灵会减速。发射器将继续以相同的速度发射

除了使用particleSpeed属性外，还有其他方法可以减缓速度，因为这将改变发射器的行为

---

我的问题受到这个问题的启发：

通常

SKEmitterNode

的速度有很多属性（

xaccelevation

，

yaccelevation

，

particleSpeedRange

，

particleScaleSpeed

）：

因此，为了实现您的请求，我认为应该可以设置

targetNode

：

/**
     Normally the particles are rendered as if they were a child of the SKEmitterNode, they can also be rendered as if they were a child of any other node in the scene by setting the targetNode property. Defaults to nil (standard behavior).
     */
    weak open var targetNode: SKNode?

你可以向苹果官方了解更多细节

下面是一些代码示例：

class GameScene: SKScene {
    var myNode :SKSpriteNode!
    var myEmitter : SKEmitterNode!
    override func didMove(to view: SKView) {
        myNode = SKSpriteNode.init(color: .red, size: CGSize(width:100,height:100))
        self.addChild(myNode)
        myNode.position = CGPoint(x:self.frame.minX,y:self.frame.midY)
        let changePos = SKAction.run{
            [weak self] in
            guard let strongSelf = self else { return }
            if strongSelf.myNode.position.x > strongSelf.frame.maxX {
                strongSelf.myNode.position.x = strongSelf.frame.minX
            }
        }
        let move = SKAction.moveBy(x: 10.0, y: 0, duration: 0.5)
        let group = SKAction.group([move,changePos])
        myNode.run(SKAction.repeatForever(SKAction.afterDelay(1.0, performAction:group)))
        let showExplosion = SKAction.repeatForever(SKAction.afterDelay(3.0, performAction:SKAction.run {
            [weak self] in
            guard let strongSelf = self else { return }
            strongSelf.myEmitter = strongSelf.newExplosion()
            strongSelf.addChild(strongSelf.myEmitter)
            strongSelf.myEmitter.targetNode = strongSelf.myNode
            strongSelf.myEmitter.particleSpeed = strongSelf.myNode.speed
            print("emitter speed is: \(strongSelf.myEmitter.particleSpeed)")
            strongSelf.myEmitter.position = CGPoint(x:strongSelf.frame.midX,y:strongSelf.frame.midY)
            strongSelf.myEmitter.run(SKAction.afterDelay(2.0, performAction:SKAction.removeFromParent()))
        }))
        self.run(showExplosion)
    }
    private func newExplosion() -> SKEmitterNode {
        let explosion = SKEmitterNode()
        let image = UIImage(named: "sparkle.png")!
        explosion.particleTexture = SKTexture(image: image)
        explosion.particleColor = UIColor.brown
        explosion.numParticlesToEmit = 100
        explosion.particleBirthRate = 450
        explosion.particleLifetime = 2
        explosion.emissionAngleRange = 360
        explosion.particleSpeed = 100
        explosion.particleSpeedRange = 50
        explosion.xAcceleration = 0
        explosion.yAcceleration = 0
        explosion.particleAlpha = 0.8
        explosion.particleAlphaRange = 0.2
        explosion.particleAlphaSpeed = -0.5
        explosion.particleScale = 0.75
        explosion.particleScaleRange = 0.4
        explosion.particleScaleSpeed = -0.5
        explosion.particleRotation = 0
        explosion.particleRotationRange = 0
        explosion.particleRotationSpeed = 0
        explosion.particleColorBlendFactor = 1
        explosion.particleColorBlendFactorRange = 0
        explosion.particleColorBlendFactorSpeed = 0
        explosion.particleBlendMode = SKBlendMode.add
        return explosion
    }
    func randomCGFloat(_ min: CGFloat,_ max: CGFloat) -> CGFloat {
        return (CGFloat(arc4random()) / CGFloat(UINT32_MAX)) * (max - min) + min
    }
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        myNode.speed = randomCGFloat(0.0,50.0)
        print("new speed is: \(myNode.speed)")
    }
}
extension SKAction {
    class func afterDelay(_ delay: TimeInterval, performAction action: SKAction) -> SKAction {
        return SKAction.sequence([SKAction.wait(forDuration: delay), action])
    }
    class func afterDelay(_ delay: TimeInterval, runBlock block: @escaping () -> Void) -> SKAction {
        return SKAction.afterDelay(delay, performAction: SKAction.run(block))
    }
}

class游戏场景：SKScene{
var myNode:SKSpriteNode！
var myEmitter:SKEmitterNode！
覆盖func didMove（到视图：SKView）{
myNode=SKSpriteNode.init（颜色：。红色，大小：CGSize（宽度：100，高度：100））
self.addChild（myNode）
myNode.position=CGPoint（x:self.frame.minX，y:self.frame.midY）
让changePos=SKAction.run{
[虚弱的自我]在
guard let strongSelf=self-else{return}
如果strongSelf.myNode.position.x>strongSelf.frame.maxX{
strongSelf.myNode.position.x=strongSelf.frame.minX
}
}
让move=SKAction.moveBy（x:10.0，y:0，持续时间：0.5）
let group=SKAction.group（[move，changePos]）
myNode.run（SKAction.repeatForever（SKAction.afterDelay（1.0，性能：组）））
让showExplosion=SKAction.repeatForever（SKAction.afterDelay）（3.0，性能：SKAction.run{
[虚弱的自我]在
guard let strongSelf=self-else{return}
strongSelf.myEmitter=strongSelf.newExplosion（）
strongSelf.addChild（strongSelf.myMitter）
strongSelf.myEmitter.targetNode=strongSelf.myNode
strongSelf.myMitter.particleSpeed=strongSelf.myNode.speed
打印（“发射器速度为：\（strongSelf.myEmitter.particleSpeed）”）
strongSelf.myEmitter.position=CGPoint（x:strongSelf.frame.midX，y:strongSelf.frame.midY）
strongSelf.myMitter.run（SKAction.afterDelay（2.0，性能：SKAction.removeFromParent（）））
}))
自运行（showExplosion）
}
私有函数newExplosion（）->SKEmitterNode{
let explosion=SKEmitterNode（）
让image=UIImage（名为：“sparkle.png”）！
explosion.particleTexture=SKTexture（图像：图像）
explosion.particleColor=UIColor.brown
explosion.numParticlesToEmit=100
爆炸。颗粒物浓度=450
explosion.particleLifetime=2
explosion.emissionAngleRange=360
爆炸。颗粒速度=100
爆炸。微粒peedrange=50
explosion.x加速度=0
爆炸加速度=0
爆炸。微粒α=0.8
explosion.particleAlphaRange=0.2
explosion.particleAlphaSpeed=-0.5
爆炸。颗粒刻度=0.75
explosion.particleScaleRange=0.4
explosion.particleScaleSpeed=-0.5
explosion.particleRotation=0
explosion.particleRotationRange=0
explosion.particle旋转速度=0
explosion.particleColorBlendFactor=1
explosion.particleColorBlendFactorRange=0
explosion.particleColorBlendFactors速度=0
explosion.particleBlendMode=SKBlendMode.add
回程爆炸
}
func randomCGFloat（umin:CGFloat，max:CGFloat）->CGFloat{
返回值（CGFloat（arc4random（））/CGFloat（UINT32_MAX））*（MAX-min）+min
}
覆盖func TouchesBegind（Touchs:Set，带有事件：UIEvent？）{
myNode.speed=randomCGFloat（0.0,50.0）
打印（“新速度为：\（myNode.speed）”）
}
}
扩展动作{
类func afterDelay（delay:TimeInterval，performation action:SKAction）->SKAction{
返回SKAction.sequence（[SKAction.wait（forDuration:delay），action]）
}
类func afterDelay（delay:TimeInterval，runBlock:@escaping（）->Void）->SKAction{
返回SKAction.afterDelay（延迟，性能：SKAction.run（块））
}
}

---

在本例中，您可以看到每次我触摸屏幕时应用于

myNode

的速度是如何涉及

mymitter

的速度的，因为发射器的

targetNode

属性设置为

myNode

，我还将

粒子速度

改为更真实的减速/加速。

你想减慢粒子的运动和粒子的发射速率吗？@我觉得很困惑（但这只是猜测，因为我还没有真正测试过）就像你们建议的那个样，每次需要为不同的发射器设置不同的值/数学，因为粒子的运动涉及到很多因素。也许你可以写一个答案来确切地说明你想要使用什么值/数学？你是否建议更改targetNode的速度会减慢粒子系统？targetNode应该会影响涉及兴趣的粒子。我没试过，也没怎么用SK粒子。SCN粒子系统的速度特性会影响现有粒子的速度及其发射率。这听起来像是达到了同样的目的。如果有用的话，@AlessandroOrnano会在我有时间的时候试试这个，谢谢。希望这能起作用，至少对于设置了targetNode的节点来说，这是一个解决方案。下面是SCNParticleSystem属性屏幕截图底部的速度值：如果你玩这个，它会减慢系统的速度

class GameScene: SKScene {
    var myNode :SKSpriteNode!
    var myEmitter : SKEmitterNode!
    override func didMove(to view: SKView) {
        myNode = SKSpriteNode.init(color: .red, size: CGSize(width:100,height:100))
        self.addChild(myNode)
        myNode.position = CGPoint(x:self.frame.minX,y:self.frame.midY)
        let changePos = SKAction.run{
            [weak self] in
            guard let strongSelf = self else { return }
            if strongSelf.myNode.position.x > strongSelf.frame.maxX {
                strongSelf.myNode.position.x = strongSelf.frame.minX
            }
        }
        let move = SKAction.moveBy(x: 10.0, y: 0, duration: 0.5)
        let group = SKAction.group([move,changePos])
        myNode.run(SKAction.repeatForever(SKAction.afterDelay(1.0, performAction:group)))
        let showExplosion = SKAction.repeatForever(SKAction.afterDelay(3.0, performAction:SKAction.run {
            [weak self] in
            guard let strongSelf = self else { return }
            strongSelf.myEmitter = strongSelf.newExplosion()
            strongSelf.addChild(strongSelf.myEmitter)
            strongSelf.myEmitter.targetNode = strongSelf.myNode
            strongSelf.myEmitter.particleSpeed = strongSelf.myNode.speed
            print("emitter speed is: \(strongSelf.myEmitter.particleSpeed)")
            strongSelf.myEmitter.position = CGPoint(x:strongSelf.frame.midX,y:strongSelf.frame.midY)
            strongSelf.myEmitter.run(SKAction.afterDelay(2.0, performAction:SKAction.removeFromParent()))
        }))
        self.run(showExplosion)
    }
    private func newExplosion() -> SKEmitterNode {
        let explosion = SKEmitterNode()
        let image = UIImage(named: "sparkle.png")!
        explosion.particleTexture = SKTexture(image: image)
        explosion.particleColor = UIColor.brown
        explosion.numParticlesToEmit = 100
        explosion.particleBirthRate = 450
        explosion.particleLifetime = 2
        explosion.emissionAngleRange = 360
        explosion.particleSpeed = 100
        explosion.particleSpeedRange = 50
        explosion.xAcceleration = 0
        explosion.yAcceleration = 0
        explosion.particleAlpha = 0.8
        explosion.particleAlphaRange = 0.2
        explosion.particleAlphaSpeed = -0.5
        explosion.particleScale = 0.75
        explosion.particleScaleRange = 0.4
        explosion.particleScaleSpeed = -0.5
        explosion.particleRotation = 0
        explosion.particleRotationRange = 0
        explosion.particleRotationSpeed = 0
        explosion.particleColorBlendFactor = 1
        explosion.particleColorBlendFactorRange = 0
        explosion.particleColorBlendFactorSpeed = 0
        explosion.particleBlendMode = SKBlendMode.add
        return explosion
    }
    func randomCGFloat(_ min: CGFloat,_ max: CGFloat) -> CGFloat {
        return (CGFloat(arc4random()) / CGFloat(UINT32_MAX)) * (max - min) + min
    }
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        myNode.speed = randomCGFloat(0.0,50.0)
        print("new speed is: \(myNode.speed)")
    }
}
extension SKAction {
    class func afterDelay(_ delay: TimeInterval, performAction action: SKAction) -> SKAction {
        return SKAction.sequence([SKAction.wait(forDuration: delay), action])
    }
    class func afterDelay(_ delay: TimeInterval, runBlock block: @escaping () -> Void) -> SKAction {
        return SKAction.afterDelay(delay, performAction: SKAction.run(block))
    }
}