Question

大家好！首先，我知道这个问题与Draw images evenly spaced along a path in iOS非常相似。但是，这是在Objective-C（我无法阅读）和它在使用CGImageRefs的普通ViewController中。我需要在swift中使用SKSpriteNodes（不是CGImageRefs）。这是我的问题：

我尝试制作一个让用户绘制简单形状（如圆圈）的程序，并沿着用户绘制的路径以固定间隔放置SKSpriteNodes。我已经让它以缓慢的速度正常工作，但是如果用户绘制太快，那么节点就会放得太远。这是我慢慢画出来的一个例子：

用户绘制的路径，节点彼此相距约60个像素。蓝色是起始节点，紫色是结束节点。

目标是每个节点都有一个物理实体，使实体不会越过用户绘制的线（这些实体不能在均匀间隔的节点之间挤压）。但是，如果用户吸引得过快，我将无法修复防御方面的差距。例如：

注意第7和第8节点之间明显较大的间隙。发生这种情况是因为我画得太快了。许多人的问题略微相似但对我的任务没有帮助（例如，沿着路径均匀地放置特定数量的节点，而不是放置尽可能多的节点以使它们沿路径分开60个像素）。

总之，这是我的主要问题：如何在任何形状的用户绘制路径上完美地间隔节点？预先感谢您的帮助！这是我的GameScene.swift文件：

import SpriteKit

导入GameplayKit

类GameScene：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)
    }
}

它可能不会很完美，但可能看起来更好。

Answer 2

我已经弄明白了！我受到了Christian Cerri建议的启发，所以我用下面的代码来制作我想要的东西：

// I added the typedef for more easily understood declarations of `p` and `end`.
typedef char array_alias_t[sizeOfAnElement];

// p's type is the same as in the previous code (char (*)[sizeOfAnElement]).
array_alias_t *p = A;

// p + x == &p[x], and &p[nElementsA] is one element past the end of A,
// which is allowed by ISO C, provided you don't dereference the pointer
// (i.e. *end is not allowed).
for (array_alias_t *end = p + nElementsA; p != end; p++) {
    if (isPositive(*p)) {
        *bStart = *p;
        bStart++;
    } else {
        *bEnd = *p;
        bEnd--;
    }
}

这导致以下结果：

无论用户移动手指的速度有多快，它都会沿着路径均匀地放置节点。非常感谢您的帮助，我希望将来可以帮助更多的人！

Swift 3沿用户

2 个答案: