如何围绕关节旋转精灵

Question

我需要让手臂和手围绕钩子的中心旋转，如下图所示，它们不分离或改变其形状(手臂和手之间的角度没有变化，只是在A处旋转)，如下图所示：

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我试着旋转手臂，但这使它们分离并改变了形状。你可以查看我下面的代码：

let hookCategoryName = "hook"
let leftArmCategoryName = "leftArm"
let rightArmCategoryName = "rightArm"
let leftHandCategoryName = "leftHand"
let rightHandCategoryName = "rightHand"

let hookCategory             : UInt32 = 0x1 << 0
let leftArmCategory            : UInt32 = 0x1 << 1
let rightArmCategory           : UInt32 = 0x1 << 2
let leftHandCategory           : UInt32 = 0x1 << 3
let rightHandCategory          : UInt32 = 0x1 << 4

extension Int {
  var degreesToRadians: Double { return Double(self) * .pi / 180 }
}
extension FloatingPoint {
  var degreesToRadians: Self { return self * .pi / 180 }
  var radiansToDegrees: Self { return self * 180 / .pi }
}

class GameScene: SKScene, SKPhysicsContactDelegate {

var hook = SKSpriteNode(imageNamed: "hook")
var leftArm = SKSpriteNode(imageNamed: "arm")
var rightArm = SKSpriteNode(imageNamed: "arm")
var leftHand = SKSpriteNode(imageNamed: "leftHand")
var rightHand = SKSpriteNode(imageNamed: "rightHand")

override func didMove(to view: SKView) {

    self.physicsWorld.gravity = CGVector(dx: 0, dy: 0)
    self.physicsWorld.contactDelegate = self

    var yellowBg = SKSpriteNode(imageNamed: "yellowBg")
    yellowBg.position = CGPoint(x: frame.midX, y: frame.midY)
    yellowBg.zPosition = 2
    addChild(yellowBg)

    hook.position = CGPoint(x: frame.midX, y: frame.midY + frame.midY/2)
    hook.zPosition = 5
    hook.name = hookCategoryName
    hook.physicsBody = SKPhysicsBody(rectangleOf: hook.frame.size)
    hook.physicsBody?.categoryBitMask = hookCategory
    hook.physicsBody?.isDynamic = false
    addChild(hook)

    rightArm.anchorPoint = CGPoint(x: 0.5, y: 1)
    rightArm.position = hook.position
    rightArm.zPosition = 5
    rightArm.name = rightArmCategoryName
    rightArm.physicsBody = SKPhysicsBody(rectangleOf: rightArm.frame.size)
    rightArm.physicsBody?.categoryBitMask = rightArmCategory

    rightArm.physicsBody!.isDynamic = true
    addChild(rightArm)

    leftArm.anchorPoint = CGPoint(x: 0.5, y: 1)
    leftArm.position = hook.position
    leftArm.zPosition = 5
    leftArm.name = leftArmCategoryName
    leftArm.physicsBody = SKPhysicsBody(rectangleOf: leftArm.frame.size)
    leftArm.physicsBody?.categoryBitMask = leftArmCategory
    leftArm.physicsBody!.isDynamic = true

    addChild(leftArm)

    // leftHand
    leftHand.anchorPoint = CGPoint(x: 0.5, y: 0.5)
    leftHand.position = CGPoint(x: leftArm.frame.minX - 22, y: leftArm.frame.minY + 7) //CGPoint(x: armLeft.position.x, y: armLeft.position.y)
    leftHand.zPosition = 5
    leftHand.name = leftHandCategoryName
    leftHand.physicsBody = SKPhysicsBody(rectangleOf: leftHand.frame.size)
    leftHand.physicsBody?.categoryBitMask = leftHandCategory

    leftHand.zRotation = CGFloat(Double(-30).degreesToRadians)//CGFloat(-Double.pi/6)
    //armLeft.physicsBody?.categoryBitMask = armCategory
    leftHand.physicsBody!.isDynamic = true

    addChild(leftHand)

    // rightHand
    rightHand.anchorPoint = CGPoint(x: 0.5, y: 0.5)
    rightHand.position = CGPoint(x: rightArm.frame.minX + 30, y: rightArm.frame.minY + 7) //CGPoint(x: armLeft.position.x, y: armLeft.position.y)
    rightHand.zPosition = 5
    rightHand.name = rightHandCategoryName

    rightHand.physicsBody = SKPhysicsBody(rectangleOf: rightHand.frame.size)
    rightHand.physicsBody?.categoryBitMask = rightHandCategory
    rightHand.zRotation = CGFloat(Double(30).degreesToRadians)//CGFloat(-Double.pi/6)
    //armLeft.physicsBody?.categoryBitMask = armCategory
    rightHand.physicsBody!.isDynamic = true

    addChild(rightHand)


    leftArm.zRotation = CGFloat(Double(-45).degreesToRadians)
    rightArm.zRotation = CGFloat(Double(45).degreesToRadians)

    rightHand.physicsBody?.contactTestBitMask = rightHandCategory
    leftHand.physicsBody?.contactTestBitMask = leftHandCategory
    rightHand.physicsBody?.collisionBitMask = rightHandCategory
    leftHand.physicsBody?.collisionBitMask = leftHandCategory


    let hookAndRightArmJoint = SKPhysicsJointPin.joint(withBodyA: hook.physicsBody!, bodyB: rightArm.physicsBody!, anchor: CGPoint(x: hook.position.x, y: self.rightArm.frame.maxY))
    self.physicsWorld.add(hookAndRightArmJoint)

    let hookAndLeftArmJoint = SKPhysicsJointPin.joint(withBodyA: hook.physicsBody!, bodyB: leftArm.physicsBody!, anchor: CGPoint(x: hook.position.x, y: self.leftArm.frame.maxY))
    self.physicsWorld.add(hookAndLeftArmJoint)


    let armsFixedJoint = SKPhysicsJointFixed.joint(withBodyA: leftArm.physicsBody!, bodyB: rightArm.physicsBody!, anchor: CGPoint.zero)
    self.physicsWorld.add(armsFixedJoint)

    //left arm and hand joint
    let leftArmAndHandJoint = SKPhysicsJointPin.joint(withBodyA: leftArm.physicsBody!, bodyB: leftHand.physicsBody!, anchor: CGPoint(x: self.leftArm.frame.minX, y: self.leftArm.frame.minY)/*CGPoint(x: armLeft.position.x, y: self.armLeft.frame.minY)*/)
    self.physicsWorld.add(leftArmAndHandJoint)

    //right arm and hand joint
    let rightArmAndHandJoint = SKPhysicsJointPin.joint(withBodyA: rightArm.physicsBody!, bodyB: rightHand.physicsBody!, anchor: CGPoint(x: self.rightArm.frame.maxX, y: self.rightArm.frame.minY)/*CGPoint(x: armLeft.position.x, y: self.armLeft.frame.minY)*/)
    self.physicsWorld.add(rightArmAndHandJoint)
}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    hook.run(SKAction.rotate(byAngle: CGFloat(Double(60).degreesToRadians), duration: 0.5))

}
}  

当运行上述代码时，旋转钩子也不会对手臂和手产生任何影响，如下图所示：

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如何获得图像第一张图像中的旋转？

Answer 1

可以使手臂和手部成为公共父节点的子节点。为此，您可以创建一个空白SKNode，如下所示：

let armsParent = SKNode()

然后，不是将手臂和手作为子对象直接添加到场景中，而是将它们作为armsParent的子对象添加，如下所示：

armsParent.addChild(leftArm)
armsParent.addChild(rightArm) // same for hands...

然后，您可以简单地使用SKAction旋转armsParent来实现您想要的效果。

或者，为了更简单，您可以直接将手臂和手作为子对象添加到hook中，如下所示：

hook.addChild(leftArm) // same for other arm and hands...

由于手臂和手是hook或armParent的子对象，因此它们的位置现在将相对于其父对象确定。因此，您可能需要更改所有.position =初始化代码来适应这种情况。