ios - Swift 3 沿用户绘制的路径生成均匀间隔的 SKSpriteNodes

Question

各位!首先，我知道这个问题与 Draw images evenly spaced along a path in iOS 非常相似。 .然而，这是在 Objective-C 中(我无法阅读)并且它在使用 CGImageRefs 的普通 ViewController 中。我需要快速使用 SKSpriteNodes(不是 CGImageRefs)。这是我的问题:

我正在尝试制作一个程序，让用户绘制一个简单的形状(如圆形)并沿着用户绘制的路径以固定间隔放置 SKSpriteNode。我已经让它以缓慢的速度正常工作，但如果用户绘制得太快，那么节点就会被放置得太远。这是我慢慢画的例子:

用户绘制的路径，节点之间的距离约为 60 像素。蓝色为起始节点，紫色为结束节点。

目标是每个节点都有一个 physicsBody，防止实体越过用户绘制的线(这些实体不能挤在均匀间隔的节点之间)。但是，如果用户画得太快，就会出现我无法修复的防御缺口。例如:

请注意第 7 个和第 8 个节点之间明显更大的间隙。发生这种情况是因为我画得太快了。许多人的问题略有相似但对我的任务没有帮助(例如，将特定数量的节点沿路径均匀分布，而不是放置尽可能多的节点以使它们沿路径相距 60 像素)。

总而言之，这又是我的主要问题:如何沿着用户绘制的任何形状的路径完美地放置节点？预先感谢您的帮助!这是我的 GameScene.swift 文件:

import SpriteKit

导入 GameplayKit

游戏场景类:SKScene {

let minDist: CGFloat = 60 //The minimum distance between one point and the next

var points: [CGPoint] = []
var circleNodes: [SKShapeNode] = []

override func didMove(to view: SKView) {


}

func getDistance (fromPoint: CGPoint, toPoint: CGPoint) -> CGFloat {

    let deltaX = fromPoint.x - toPoint.x
    let deltaY = fromPoint.y - toPoint.y

    let deltaXSquared = deltaX*deltaX
    let deltaYSquared = deltaY*deltaY

    return sqrt(deltaXSquared + deltaYSquared) //Return the distance

}


func touchDown(atPoint pos : CGPoint) {

    self.removeAllChildren()

    //The first time the user touches, we need to place a point and mark that as the firstCircleNode
    print(pos)
    points.append(pos)
    //allPoints.append(pos)

    let firstCircleNode = SKShapeNode(circleOfRadius: 5.0)

    firstCircleNode.fillColor = UIColor.blue

    firstCircleNode.strokeColor = UIColor.blue

    firstCircleNode.position = pos

    circleNodes.append(firstCircleNode)

    self.addChild(firstCircleNode)

}

func touchMoved(toPoint pos : CGPoint) {

    let lastIndex = points.count - 1 //The index of the last recorded point

    let distance = getDistance(fromPoint: points[lastIndex], toPoint: pos)
        //vector_distance(vector_double2(Double(points[lastIndex].x), Double(points[lastIndex].y)), vector_double2(Double(pos.x), Double(pos.y))) //The distance between the user's finger and the last placed circleNode

    if distance >= minDist {
        points.append(pos)

        //Add a box to that point
        let newCircleNode = SKShapeNode(circleOfRadius: 5.0)

        newCircleNode.fillColor = UIColor.red

        newCircleNode.strokeColor = UIColor.red

        newCircleNode.position = pos

        circleNodes.append(newCircleNode)

        self.addChild(newCircleNode)

    }

}

func touchUp(atPoint pos : CGPoint) {

    //When the user has finished drawing a circle:

    circleNodes[circleNodes.count-1].fillColor = UIColor.purple //Make the last node purple

    circleNodes[circleNodes.count-1].strokeColor = UIColor.purple

    //Calculate the distance between the first placed node and the last placed node:
    let distance = getDistance(fromPoint: points[0], toPoint: points[points.count-1])
        //vector_distance(vector_double2(Double(points[0].x), Double(points[0].y)), vector_double2(Double(points[points.count - 1].x), Double(points[points.count - 1].y)))

    if distance <= minDist { //If the distance is closer than the minimum distance

        print("Successful circle")

    } else { //If the distance is too far

        print("Failed circle")

    }

    points = []
    circleNodes = []

}


override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches { self.touchDown(atPoint: t.location(in: self)) }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches { self.touchMoved(toPoint: t.location(in: self)) }
}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches { self.touchUp(atPoint: t.location(in: self)) }
}

override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches { self.touchUp(atPoint: t.location(in: self)) }
}


override func update(_ currentTime: TimeInterval) {
    // Called before each frame is rendered
}

Answer 1

您可以尝试调整矢量的大小:

func touchMoved(toPoint pos : CGPoint) {
    let lastIndex = points.count - 1 //The index of the last recorded point
    let distance = getDistance(fromPoint: points[lastIndex], toPoint: pos)
    if distance >= minDist {
        // find a new "pos" which is EXACTLY minDist distant
        let vx = pos.x - points[lastIndex].x
        let vy = pos.y - points[lastIndex].y
        vx /= distance
        vy /= distance
        vx *= minDist
        vy *= minDist
        let newpos = CGPoint(x: vx, y:vy)
        points.append(newpos)

        //Add a box to that point
        let newCircleNode = SKShapeNode(circleOfRadius: 5.0)
        newCircleNode.fillColor = UIColor.red
        newCircleNode.strokeColor = UIColor.red
        newCircleNode.position = newpos // NOTE
        circleNodes.append(newCircleNode)
        self.addChild(newCircleNode)
    }
}

它可能不完美，但可能看起来更好。