如何对圆形SKPhysicsBody施加摩擦力

Question

我试图在SpriteKit中理解摩擦或物理学的其他方面。我创建了一个旋转的圆圈。我在旋转圆圈的顶部放置了一个正方形。我预计广场会随着圆圈一起旋转而掉落，但是方形不会移动。我设置physicsBody.friction = 1.0试图使表面变粘，但它没有帮助。我需要对物理进行哪些更改才能使方块受到圆周旋转的影响？

我使用Playground创建了一个自包含的示例。测试：

1. 下载附件bluecircle.png并将其放在桌面上（或任何地方）
2. 将以下代码复制到您的Playground
3. 将NSImage路径更改为您保存的任何地方bluecircle.png

代码：

import Cocoa
import SpriteKit
import XCPlayground

let screenWidth = 1400.0
let screenHeight = 1000.0
let xOffset = 300.0

let smallsquareSize = CGSize(width: 100, height: 100)
let bluesquareSize = CGSize(width: 400 , height: 400)
// the img is a blue circle w/ radius of 200 located on my desktop
let img = NSImage(byReferencingFile: "/Users/CHANGETHIS/Desktop/bluecircle.png")

class PlayScene: SKScene {

    let redsquare = SKSpriteNode(color: SKColor.redColor(), size: smallsquareSize)
    let greensquare = SKSpriteNode(color: SKColor.greenColor(), size: smallsquareSize)
    let bluesquare = SKSpriteNode(color: SKColor.blueColor(), size: bluesquareSize)
    let bluecircle = SKSpriteNode(texture: SKTexture(image: img))

    var lastTime = NSTimeInterval(0)


    init(size: CGSize) {
        super.init(size: size)
    }


    override func didMoveToView(view: SKView!) {

        backgroundColor = SKColor.blackColor()

        // RED SQUARE
        redsquare.position = CGPoint(x: screenWidth/2 - xOffset, y: screenHeight - 100)
        redsquare.physicsBody = SKPhysicsBody(rectangleOfSize: smallsquareSize)
        redsquare.physicsBody.friction = 1.0
        addChild(redsquare)

        // BLUE SQUARE
        bluesquare.position = CGPoint(x: screenWidth / 2 - xOffset, y: screenHeight / 2)
        bluesquare.physicsBody = SKPhysicsBody(rectangleOfSize: bluesquareSize)
        bluesquare.physicsBody.dynamic = false
        bluesquare.physicsBody.affectedByGravity = false
        bluesquare.physicsBody.friction = 1.0
        addChild(bluesquare)


        // GREEN SQUARE
        greensquare.position = CGPoint(x: screenWidth/2 + xOffset, y: screenHeight - 100)
        greensquare.physicsBody = SKPhysicsBody(rectangleOfSize: smallsquareSize)
        greensquare.physicsBody.friction = 1.0
        addChild(greensquare)

        // BLUE CIRCLE
        bluecircle.position = CGPoint(x: screenWidth / 2 + xOffset, y: screenHeight / 2)
        bluecircle.physicsBody = SKPhysicsBody(circleOfRadius: 200)
        bluecircle.physicsBody.dynamic = false
        bluecircle.physicsBody.affectedByGravity = false
        bluecircle.physicsBody.friction = 1.0
        addChild(bluecircle)

    }

    override func update(currentTime: NSTimeInterval) {
        let delta = currentTime - lastTime
        lastTime = currentTime

        bluesquare.zRotation += delta
        bluecircle.zRotation += delta

    }
}

var view = SKView(frame:NSRect(x: 0.0, y: 0.0, width: screenWidth, height: screenHeight))
var playScene = PlayScene(size: CGSize(width: screenWidth, height: screenHeight))

view.presentScene(playScene)
view.showsFPS = true
view.showsDrawCount = true
view.showsNodeCount = true
XCPShowView("View", view)

`

Answer 1

我认为你问题的答案是关节。在你的节点之间创建一个固定的联合我相信会解决你的问题。

https://developer.apple.com/library/ios/documentation/SpriteKit/Reference/SKPhysicsJoint_Ref/Reference/Reference.html