以一定速度在屏幕上随机移动物体
Posted
技术标签:
【中文标题】以一定速度在屏幕上随机移动物体【英文标题】：Moving objects random across the screen with a certain speed 【发布时间】：2017-05-25 08:48:11 【问题描述】：我需要让我的对象在屏幕上随机移动。当它们移动时，该对象正在寻找一定半径范围内的另一个对象。
我找到了下面的链接，并实现了 getDuration 函数。但我和主题所有者有同样的故障。我可以看到它应该可以通过删除正在运行的操作来修复。
Moving an object across the screen at a certain speed.(Sprite Kit)
视频：https://www.youtube.com/watch?v=jHE5RC-mvwU
但我现在尝试了几种解决方案，但我无法使其工作。当我终止动作时，我的对象会停止移动。
谁能告诉我，在哪里杀死我的动作，在 moveToWaypoint 中创建？我需要我的对象移动到一个随机的航点，但如果一个特定的对象进入半径范围内，那么它应该为壁橱对象设置一个新的航点并再次开始操作。
代码：
///Called in update method
func move(scene: GameplayScene)
checkForWaypoint()
checkForFood(scene: scene)
moveToWaypoint()
///Creates a new waypoint
func createWaypoint()
waypoint = CGPoint(x: randomBetweenNumbers(firstNum: minX, secondNum: maxX), y: randomBetweenNumbers(firstNum: minX, secondNum: maxX))
override func checkForFood(scene: GameplayScene)
var closesObject: SKNode? = nil
scene.enumerateChildNodes(withName: "Food")
node, _ in
let distance = node.position.distanceFromCGPoint(point: self.position)
if distance < self.FOOD_RANGE
closesObject = node
if hungryState == HungryState.hungry
if closesObject != nil
waypoint = closesObject?.position
moveState = MoveState.movingToFood
else
if moveState == MoveState.movingToFood
createWaypoint()
///Moves the object to the waypoint
func moveToWaypoint ()
let action = SKAction.move(to: waypoint!, duration: getDuration(pointA: position, pointB: waypoint!, speed: 25))
self.run(action)
///Calcuate a speed between to cordinates
private func getDuration(pointA:CGPoint,pointB:CGPoint,speed:CGFloat)-> TimeInterval
let xDist = (pointB.x - pointA.x)
let yDist = (pointB.y - pointA.y)
let distance = sqrt((xDist * xDist) + (yDist * yDist));
let duration : TimeInterval = TimeInterval(distance/speed)
return duration
编辑：
Gamescene 类的更新函数
override func update(_ currentTime: TimeInterval)
moveFish()
private func moveFish()
for node in self.children
if node.name != nil
switch node.name
case "Fish"?:
let fishToMove = node as! Fish
fishToMove.move(scene: self)
default:
break
【问题讨论】：
你能说明如何从场景的 update() 方法中调用 move() 方法吗？我只是感兴趣它是严格调用每一帧还是有一些自定义逻辑？如果答案是“是的，我每帧都调用 move 方法......因此我每帧都创建 SKAction”，那将是你的第一个错误。您将要实现的目标应该很容易。也可以使用物理接触检测来完成。但这只是我:) 它是在场景中的update()方法中调用的，是的。你能给我一些细节，如何解决这个@Whirlwind？这是我的第一个 SpriteKit 应用，所以我还是新手 :) 我只问了几个问题，你没有回答 :) 尝试仔细阅读我提出的问题，以便继续调试。 我刚刚更新了@Whirlwind 的问题。我添加了更新函数和 moveFish() - 它调用了 move() 函数。 好吧，我个人只会在需要时执行操作，而不是每次都执行。关于错误本身......实际问题是什么？ （抱歉，我目前没有时间阅读其他问题）。 【参考方案1】：您在此处尝试解决的问题可以通过两种方式完成。首先是使用物理，其次当然是没有它。我决定不使用物理，因为这显然是你的做法。
简而言之，这些示例中的鱼在没有食物的情况下使用SKAction 移动。当食物在范围内时，使用 update: 方法将鱼移动到它们的目标。当鱼吃掉它时，它会继续使用SKAction 移动。
此外，在此之前，我从 *** 借用了一些有用的扩展，将来您可能会发现它们很有用：
import SpriteKit
import GameplayKit
//Extension borrowed from here : https://***.com/a/40810305
extension ClosedRange where Bound : FloatingPoint
public func random() -> Bound
let range = self.upperBound - self.lowerBound
let randomValue = (Bound(arc4random_uniform(UINT32_MAX)) / Bound(UINT32_MAX)) * range + self.lowerBound
return randomValue
//Extension borrowed from here : https://***.com/a/37760551
extension CGRect
func randomPoint() -> CGPoint
let origin = self.origin
return CGPoint(x:CGFloat(arc4random_uniform(UInt32(self.width))) + origin.x,
y:CGFloat(arc4random_uniform(UInt32(self.height))) + origin.y)
//Extension borrowed from here: https://***.com/a/33292919
extension CGPoint
func distance(point: CGPoint) -> CGFloat
return abs(CGFloat(hypotf(Float(point.x - x), Float(point.y - y))))
现在有一个像你这样的 Fish 类，它的方法很少，还有一个物理体，仅用于检测食物和鱼之间的接触，但这一切都来自物理。这是 Collider 结构，以防您想知道我是如何定义它的：
struct Collider
static let food : UInt32 = 0x1 << 0
static let fish : UInt32 = 0x1 << 1
static let wall : UInt32 = 0x1 << 2
现在回到 Fish 类...我已将 cmets 放入代码中，所以我想不需要解释这些方法的作用。代码如下：
class Fish:SKSpriteNode
private let kMovingAroundKey = "movingAround"
private let kFishSpeed:CGFloat = 4.5
private var swimmingSpeed:CGFloat = 100.0
private let sensorRadius:CGFloat = 100.0
private weak var food:SKSpriteNode! = nil //the food node that this fish currently chase
override init(texture: SKTexture?, color: UIColor, size: CGSize)
super.init(texture: texture, color: color, size: size)
physicsBody = SKPhysicsBody(rectangleOf: size)
physicsBody?.affectedByGravity = false
physicsBody?.categoryBitMask = Collider.fish
physicsBody?.contactTestBitMask = Collider.food
physicsBody?.collisionBitMask = 0x0 //No collisions with fish, only contact detection
name = "fish"
let sensor = SKShapeNode(circleOfRadius: 100)
sensor.fillColor = .red
sensor.zPosition = -1
sensor.alpha = 0.1
addChild(sensor)
func getDistanceFromFood()->CGFloat?
if let food = self.food
return self.position.distance(point: food.position)
return nil
func lock(food:SKSpriteNode)
//We are chasing a food node at the moment
if let currentDistanceFromFood = self.getDistanceFromFood()
if (currentDistanceFromFood > self.position.distance(point: food.position))
//chase the closer food node
self.food = food
self.stopMovingAround()
//else, continue chasing the last locked food node
//We are not chasing the food node at the moment
else
//go and chase then
if food.position.distance(point: self.position) <= self.sensorRadius
self.food = food
self.stopMovingAround()
//Helper method. Not used currently. You can use this method to prevent chasing another (say closer) food while already chasing one
func isChasing(food:SKSpriteNode)->Bool
if self.food != nil
if self.food == food
return true
return false
func stopMovingAround()
if self.action(forKey: kMovingAroundKey) != nil
removeAction(forKey: kMovingAroundKey)
//MARK: Chasing the food
//This method is called many times in a second
func chase(within rect:CGRect)
guard let food = self.food else
if action(forKey: kMovingAroundKey) == nil
self.moveAround(within: rect)
return
//Check if food is in the water
if rect.contains(food.frame.origin)
//Take a detailed look in my *** answer of how chasing works : https://***.com/a/36235426
let dx = food.position.x - self.position.x
let dy = food.position.y - self.position.y
let angle = atan2(dy, dx)
let vx = cos(angle) * kFishSpeed
let vy = sin(angle) * kFishSpeed
position.x += vx
position.y += vy
required init?(coder aDecoder: NSCoder)
fatalError("init(coder:) has not been implemented")
func moveAround(within rect:CGRect)
if scene != nil
//Go randomly around the screen within view bounds
let point = rect.randomPoint()
//Formula: time = distance / speed
let duration = TimeInterval(point.distance(point: position) / self.swimmingSpeed)
let move = SKAction.move(to: point, duration: duration)
let block = SKAction.run
[unowned self] in
self.moveAround(within: rect)
let loop = SKAction.sequence([move,block])
run(loop, withKey: kMovingAroundKey)
所以基本上，有一些方法可以在鱼不追逐食物的时候四处移动。还有一种方法可以停止这个（无限）动作（SKAction）。最重要的方法是chase(within rect:) 方法。该方法在场景的 update() 方法中调用，并定义鱼将（尝试）追逐食物的方式和时间。
现在是游戏场景：
//MARK: GameScene
class GameScene: SKScene, SKPhysicsContactDelegate
private var nodesForRemoval:[SKNode] = []
private var water = SKSpriteNode()
override func didMove(to view: SKView)
physicsWorld.contactDelegate = self
physicsWorld.gravity = CGVector(dx: 0.0, dy: -0.5)
physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
physicsBody?.categoryBitMask = Collider.wall
physicsBody?.contactTestBitMask = 0x0
physicsBody?.collisionBitMask = Collider.fish | Collider.food
self.backgroundColor = .white
//Water setup
water = SKSpriteNode(color: .blue, size: CGSize(width: frame.width, height: frame.height - 150))
water.position = CGPoint(x: 0, y: -75)
water.alpha = 0.3
addChild(water)
water.zPosition = 4
//Fish one
let fish = Fish(texture: nil, color: .black, size:CGSize(width: 20, height: 20))
addChild(fish)
fish.position = CGPoint(x: frame.midX-50, y: frame.minY + 100)
fish.zPosition = 5
fish.moveAround(within: water.frame)
//Fish two
let fish2 = Fish(texture: nil, color: .black, size:CGSize(width: 20, height: 20))
addChild(fish2)
fish2.position = CGPoint(x: frame.midX+50, y: frame.minY + 100)
fish2.zPosition = 5
fish2.moveAround(within: water.frame)
func feed(at position:CGPoint, with food:SKSpriteNode)
food.position = CGPoint(x: position.x, y: frame.size.height/2 - food.frame.size.height)
addChild(food)
//MARK: Food factory :)
func getFood()->SKSpriteNode
let food = SKSpriteNode(color: .purple, size: CGSize(width: 10, height: 10))
food.physicsBody = SKPhysicsBody(rectangleOf: food.frame.size)
food.physicsBody?.affectedByGravity = true
food.physicsBody?.categoryBitMask = Collider.food
food.physicsBody?.contactTestBitMask = Collider.fish
food.physicsBody?.collisionBitMask = Collider.wall
food.physicsBody?.linearDamping = (0.1 ... 0.95).random()
food.name = "food"
return food
//MARK: Feeding
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?)
if let touch = touches.first
let location = touch.location(in: self)
let food = getFood()
feed(at: location, with: food)
//MARK: Eating
func didBegin(_ contact: SKPhysicsContact)
guard let nodeA = contact.bodyA.node, let nodeB = contact.bodyB.node else
//Silliness like removing a node from a node tree before physics simulation is done will trigger this error
fatalError("Physics body without its node detected!")
let mask = contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask
switch mask
//Contact between fish and a food
case Collider.fish | Collider.food:
if let food = (contact.bodyA.categoryBitMask == Collider.food ? nodeA : nodeB) as? SKSpriteNode
self.nodesForRemoval.append(food)
default:
//some unknown contact occurred
break
//MARK: Removing unneeded nodes
override func didSimulatePhysics()
for node in self.nodesForRemoval
node.removeFromParent()
self.nodesForRemoval.removeAll()
//MARK: Chasing the food
override func update(_ currentTime: TimeInterval)
self.enumerateChildNodes(withName: "fish")
[unowned self] node, stop in
if let fish = node as? Fish
self.enumerateChildNodes(withName: "food")
node, stop in
fish.lock(food: node as! SKSpriteNode)
fish.chase(within: self.water.frame)
就是这样。在这里，我们设置我们的节点，解决接触检测并告诉哪些鱼应该追逐哪个食物节点。我离开了 cmets，所以一切都在那里。我希望这些方法几乎是不言自明的，但当然您可以向我询问有关工作原理的详细信息。
这里有一段简短的视频介绍了它的工作原理：
以及更长的版本，因为我只能上传两个 2 兆字节：screen recording
基本上，如果食物节点不在其定义的范围内，鱼就不会追逐它。尽管如此，鱼仍会追逐锁定的节点，直到它吃掉它。但是如果有一些其他的食物更接近，鱼就会追逐那个食物节点。当然这不是必须的，你可以随意调整（检查isChasing:）方法。
【讨论】：
谢谢！很好的答案。 @Grumme 欢迎您！请注意，swimmingSpeed 或 sensorRadius 之类的内容可能会通过 Fish 类的自定义初始化程序传递。这样你就可以让每条鱼都与众不同。
同样在GameViewController 的viewDidLoad() 中，当从sks 文件加载场景时，您应该设置scene.size = view.bounds.size 并设置aspectFill 的缩放模式，以便此代码像视频中一样工作.
我刚刚实施并开始测试您的解决方案@Whirlwind，但我的鱼似乎加速了？当半径内有食物时，鱼会得到“提升”。请看这个视频：giphy.com/gifs/3o7btUkxKM96u9iVk4鱼应该保持匀速:)。
@Grumme 当然，设置正确的速度取决于您。 :) 您可能需要设置其他内容。我只是向你展示了你可以走哪条路，实现随机移动+追逐目标。以上是关于以一定速度在屏幕上随机移动物体的主要内容，如果未能解决你的问题，请参考以下文章