我被要求简化这个问题,所以这就是我正在做的事情。
我在 SpriteKit 的物理关节(以及可能的物理身体属性)中苦苦挣扎。我尝试了每个子类和许多配置,但接缝好像没有任何效果,或者我做错了什么。
我正在开发贪吃蛇游戏。用户控制蛇头,它应该以恒定的速度向前移动,用户可以顺时针或逆时针转动它。所有剩余的蛇的碎片都应该跟随头部——它们应该沿着前一段时间头部的路径移动。
我认为对于这个游戏,Pin 关节应该是答案,哪个锚点恰好位于元素之间的中心。
不幸的是,结果并不完美。结构应该形成完美的圆圈,但事实并非如此。我附上代码和显示当前效果的 gif。有没有人有足够的经验给我任何建议,身体和/或关节的哪些特性应该在这里应用以获得预期的效果?
我的代码:
class GameScene: SKScene {
private var elements = [SKNode]()
override func didMove(to view: SKView) {
physicsWorld.gravity = CGVector(dx: 0, dy: 0)
let dummyTurnNode = SKNode()
dummyTurnNode.position = CGPoint(x: size.width / 2 - 50, y: size.height / 2)
let dummyTurnBody = SKPhysicsBody(circleOfRadius: 1)
dummyTurnBody.isDynamic = false
dummyTurnNode.physicsBody = dummyTurnBody
addChild(dummyTurnNode)
for index in 0..<5 {
let element = SKShapeNode(circleOfRadius: 10)
let body = SKPhysicsBody(circleOfRadius: 10)
body.linearDamping = 0
// body.mass = 0
element.physicsBody = body
element.position = CGPoint(x: size.width / 2, y: size.height / 2 - 30 * CGFloat(index))
elements.append(element)
addChild(element)
let label = SKLabelNode(text: "A")
label.fontSize = 10
label.fontName = "Helvetica-Bold"
element.addChild(label)
if index == 0 {
element.fillColor = UIColor.blue()
body.velocity = CGVector(dx: 0, dy: 30)
let dummyTurnJoint = SKPhysicsJointPin.joint(withBodyA: dummyTurnBody, bodyB: body, anchor: dummyTurnNode.position)
physicsWorld.add(dummyTurnJoint)
} else {
body.linearDamping = 1
element.fillColor = UIColor.red()
let previousElement = elements[index - 1]
let connectingJoint = SKPhysicsJointPin.joint(withBodyA: previousElement.physicsBody!, bodyB: body, anchor: CGPoint(x: size.width / 2, y: size.height / 2 - 30 * CGFloat(index) + CGFloat(15)))
physicsWorld.add(connectingJoint)
}
}
}
override func update(_ currentTime: TimeInterval) {
let head = elements.first!.physicsBody!
var velocity = head.velocity
velocity.normalize()
velocity.multiply(30)
head.velocity = velocity
}
}
extension CGVector {
var rwLength: CGFloat {
let xSq = pow(dx, 2)
let ySq = pow(dy, 2)
return sqrt(xSq + ySq)
}
mutating func normalize() {
dx /= rwLength
dy /= rwLength
}
mutating func multiply(_ factor: CGFloat) {
dx *= factor
dy *= factor
}
}