GameplayKit > 让代理在目标后停止移动以跟随路径

Question

我通过在其行为中添加目标 toFollow: GKPath 来使代理遵循 GKPath。一切正常，但是当到达路径上的目标点时，代理会继续以类似 8 的形状移动。如何防止代理在到达 GKPath 上的目标点时徘徊？

我想到的一个解决方案是在接近目标点时设置另一个目标 toReachTargetSpeed: 0.0。但是，我不确定最佳做法是什么，因为没有内置方法可以查看目标何时“完成”。

1. 是否在每次更新时使用 IF 语句检查目标距离：？性能如何？
2. 我是否使用某种 GKRule？

您的建议将不胜感激。谢谢。

Answer 1

我选择了第一个选项，即在移动组件更新函数中跟踪到目标的距离：

override func update(deltaTime seconds: TimeInterval) {
    guard let entity = self.entity as? BaseEntity else { return }
    if entity.moving {
        let targetPoint = CGPoint(x: 100, y: 100)
        let distanceToTarget = distanceFrom(point: point)
        if distanceToTarget < GameConfiguration.Movement.targetProximity {
            stopMovement(afterTraversing: distanceToTarget)
        }
    }
}

func distanceFrom(point: CGPoint) -> Float {
    guard let entity = self.entity as? BaseEntity else { return CGFloat.greatestFiniteMagnitude }
    let dx = point.x - entity.visualComponent.node.position.x
    let dy = point.y - entity.visualComponent.node.position.y
    return hypotf(Float(dx), Float(dy))
}

当代理离目标足够近时，运行 stopMovement 函数。反过来，这将计算通过剩余距离到目标所需的时间（具有恒定速度），并将设置一个计时器来确定何时强制停止代理：

func stopMovement(afterTraversing distance: Float) {
    guard let entity = self.entity as? BaseEntity else { return }
    guard (entity.moving) else { return }
    guard let behavior = entity.agent.behavior as? MovingBehavior else { return }
    let timeToTarget = TimeInterval(distance / entity.agent.maxSpeed)
    Timer.scheduledTimer(withTimeInterval: timeToTarget, repeats: false, block: {_ in
        behavior.stopMoving()
        entity.agent.maxSpeed = 0.0
        entity.moving = false
    })
}

class MovingBehavior: GKBehavior {

    var reachMaxSpeed: GKGoal
    var followPathGoal: GKGoal
    var stopMovingGoal = GKGoal(toReachTargetSpeed: 0.0)

    init(path: GKPath, target: GKGraphNode, maxSpeed: Float) {
        reachMaxSpeed = GKGoal(toReachTargetSpeed: maxSpeed)
        followPathGoal = GKGoal(toFollow: path, maxPredictionTime: 1.0, forward: true)
        super.init()
        setWeight(1.0, for: reachMaxSpeed)
        setWeight(0.8, for: followPathGoal)
        setWeight(0.0, for: stopMovingGoal)
    }

    func stopMoving() {
        setWeight(0.0, for: reachMaxSpeed)
        setWeight(0.0, for: followPathGoal)
        setWeight(1.0, for: stopMovingGoal)
    }
}