SKNode在SKConstraint范围内跟随另一个SKNode

Question

我正在尝试使用SpriteKit模拟眼睛。

眼睛的瞳孔在屏幕上移动时跟踪用户的手指，但必须保持在眼睛的范围内。

我尝试使用SKConstraint解决此问题，但未成功。

编辑

我的想法是将SKConstraints应用于瞳孔以将其边界限制在眼睛范围内。任何触摸（即touchesMoved（）等）都将以SKAction.moveTo（）的形式应用于瞳孔，并且SpriteKit手柄将瞳孔保持在视线范围内。

let touchPoint = CGPoint()
SKAction.moveTo( touchPoint, duration: 2)

该视频的代码可用：https：//gist.github.com/anonymous/f2356e07d1ac0e67c25b1940662d72cb

一张图片胜过千言万语...

想象瞳孔是白色的小圆圈。蓝色框模拟用户在屏幕上移动手指。

理想情况下，瞳孔遵循屏幕周围的蓝色框，并遵循由黄色圆圈定义的路径。

iOS 10 | 雨燕3 | Xcode 8

Answer 1

您可以使用方向约束来旋转节点以使其面向触摸位置，而无需按距离进行约束。通过将具有x偏移量的“瞳孔”节点添加到受约束的节点，瞳孔将朝着触摸点移动。这是如何执行此操作的示例：

let follow = SKSpriteNode(color:.blue, size:CGSize(width:10,height:10))
let pupil = SKShapeNode(circleOfRadius: 10)
let container = SKNode()
let maxDistance:CGFloat = 25

override func didMove(to view: SKView) {
    addChild(container)
    // Add the pupil at an offset
    pupil.position = CGPoint(x: maxDistance, y: 0)
    container.addChild(pupil)

    // Node that shows the touch point
    addChild(follow)

    // Add an orientation constraint to the container
    let range = SKRange(constantValue: 0)        
    let constraint = SKConstraint.orient(to: follow, offset: range)
    container.constraints = [constraint]
}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches {
        let location = t.location(in: self)
        follow.position = location
        adjustPupil(location: location)
    }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches {
        let location = t.location(in: self)
        follow.position = location
        adjustPupil(location: location)
    }
 }

// Adjust the position of the pupil within the iris
func adjustPupil(location:CGPoint) {
    let dx = location.x - container.position.x
    let dy = location.y - container.position.y
    let distance = sqrt(dx*dx + dy*dy)
    let x = min(distance, maxDistance)
    pupil.position = CGPoint(x:x, y:0)
}