在没有framedrops的情况下创建无限的cgpath

Question

我需要不断创建一个cgpath.目前我这样做:

 func createLine(){
        var rand = randomBetweenNumbers(1, 2)
        currentY--
        if rand < 1.5{
            currentX--
            CGPathAddLineToPoint(leftPath, nil, currentX, currentY)
        }else{
            currentX++
            CGPathAddLineToPoint(leftPath, nil, currentX, currentY)
        }
        CGPathAddLineToPoint(rightPath, nil, currentX+tileSize, currentY)
        lineNode.path = leftPath
        rightNode.path = rightPath

}

并称之为:

NSTimer.scheduledTimerWithTimeInterval(0.05, target: self, selector: Selector("startTile"), userInfo: nil, repeats: true)

但问题是,帧随着时间的推移越来越低.有什么我必须改变,以便帧率不再下降？

我的目标是创建一个随机的无尽路径.

Answer 1

在绘制逐渐增加的线条数的同时保持高 FPS 计数的关键是快速达到向场景添加更多线条对帧速率影响很小或没有影响的状态。至少有两种方法可以实现这一点。

两者中最直接的方法是定期将先前绘制的线条转换为 anSKTexture并将结果显示为 an 的纹理SKSpriteNode。步骤如下：

1. 创建一个SKNode用作线路容器
2. 创建一个SKSpriteNode将用作线条画布
3. 创建一个SKShapeNode用于绘制新线的
4. 将容器添加到场景中，并将画布和形状节点添加到容器中
5. path使用形状节点的属性绘制一组连接的线段
6. 当行数达到预定值时，将容器的内容转换为“SKTexture”
7. 将画布的纹理属性设置为SKTexture. 请注意，由于画布也是容器的子级，因此它的内容也会添加到纹理中
8. 起泡沫，冲洗，重复步骤 5 - 7

下面是一个用 Swift 实现的示例，它在 iPhone 6 设备上以 60 FPS 的速度绘制了一组无尽的线条（您应该在设备上测试性能，而不是使用模拟器）：

class GameScene: SKScene {
    // 1. Create container to hold new and old lines
    var lineContainer = SKNode()
    // 2. Create canvas
    var lineCanvas:SKSpriteNode?
    // 3. Create shape to draw new lines
    var lineNode = SKShapeNode()

    var lastDrawTime:Int64 = 0
    var lineCount = 0
    var timeScan:Int64 = 0
    var path = CGPathCreateMutable()

    var lastPoint = CGPointZero

    override func didMoveToView(view:SKView) {
        scaleMode = .ResizeFill

        // 4. Add the container to the scene and the canvas to the container 
        addChild(lineContainer)
        lineCanvas = SKSpriteNode(color:SKColor.clearColor(),size:view.frame.size)
        lineCanvas!.anchorPoint = CGPointZero
        lineCanvas!.position = CGPointZero
        lineContainer.addChild(lineCanvas!)
        lastPoint = CGPointMake(view.frame.size.width/2.0, view.frame.size.height/2.0)
    }

    // Returns a random value in the specified range
    func randomInRange(minValue:CGFloat, maxValue:CGFloat) -> CGFloat {
        let r = CGFloat(Double(arc4random_uniform(UInt32.max))/Double(UInt32.max))
        return (maxValue-minValue) * r + minValue
    }

    func drawLine() {
        if (CGPathIsEmpty(path)) {
            // Create a new line that starts where the previous line ended
            CGPathMoveToPoint(path, nil, lastPoint.x, lastPoint.y)
            lineNode.path = nil
            lineNode.lineWidth = 1.0
            lineNode.strokeColor = SKColor.blueColor()
            lineNode.zPosition = 100
            lineContainer.addChild(lineNode)
        }
        // Add a random line segment
        let x = randomInRange(size.width*0.1, maxValue: size.width*0.9)
        let y = randomInRange(size.height*0.1, maxValue: size.height*0.9)
        CGPathAddLineToPoint(path, nil, x, y)
        lineNode.path = path
        // Save the current point so we can connect the next line to the end of the last line
        lastPoint = CGPointMake(x, y)
    }

    override func update(currentTime: CFTimeInterval) {
        let lineDrawTime = timeScan / 10
        // 5. Draw a new line every 10 updates. Increment line count
        if (lineDrawTime != lastDrawTime) {
            drawLine()
            ++lineCount
        }
        // 6. and 7. Add all newly and previously drawn lines to the canvas
        if (lineCount == 8) {
            addLinesToTexture()
            lineCount = 0
        }
        lastDrawTime = lineDrawTime
        ++timeScan
    }

    func addLinesToTexture () {
        // Convert the contents of the line container to an SKTexture
        let texture = self.view!.textureFromNode(lineContainer)
        // Display the texture
        lineCanvas!.texture = texture
        // Start a new line
        lineNode.removeFromParent()
        path = CGPathCreateMutable()
    }
}