How to keep a 30˚ distance between two lines anchored at a point

Question

I am trying to create two lines that are anchored at a certain point (sprite) and rotate to form a 30 degree angle between them. Below is an image what I want to achieve.

This is what I've done so far:

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 anchorSprite = SKSpriteNode(imageNamed: "anchorSprite")
var armLeft = SKSpriteNode(imageNamed: "lineSprite")
var armRight = SKSpriteNode(imageNamed: "lineSprite")

override func didMove(to view: SKView) {

    self.physicsWorld.gravity = CGVector(dx: 0, dy: -1.8)
    self.physicsWorld.contactDelegate = self

    var tealBg = SKSpriteNode(imageNamed: "tealBg")
    tealBg.position = CGPoint(x: frame.midX, y: frame.midY)
    tealBg.zPosition = 10
    addChild(tealBg)

    anchorSprite.position = CGPoint(x: frame.midX, y: frame.midY + frame.midY/2)
    anchorSprite.zPosition = 20

    anchorSprite.physicsBody = SKPhysicsBody(rectangleOf: anchorSprite.frame.size)
    anchorSprite.physicsBody?.categoryBitMask = pinCategory
    anchorSprite.physicsBody?.isDynamic = false

    addChild(anchorSprite)

    armRight.anchorPoint = CGPoint(x: 0.5, y: 1)
    armRight.position = anchorSprite.position
    armRight.zPosition = 20
    armRight.physicsBody = SKPhysicsBody(rectangleOf: armRight.frame.size)
    armRight.zRotation = CGFloat(Double(15).degreesToRadians)//CGFloat(Double.pi/6)
    armRight.physicsBody!.isDynamic = true
    addChild(armRight)

    armLeft.anchorPoint = CGPoint(x: 0.5, y: 1)
    armLeft.position = anchorSprite.position
    armLeft.zPosition = 20
    armLeft.physicsBody = SKPhysicsBody(rectangleOf: armRight.frame.size)
    armLeft.zRotation = CGFloat(Double(-15).degreesToRadians)//CGFloat(-Double.pi/6)
    armLeft.physicsBody!.isDynamic = true
    addChild(armLeft)

    //Pin joints
    var pinAndRightArmJoint = SKPhysicsJointPin.joint(withBodyA: anchorSprite.physicsBody!, bodyB: armRight.physicsBody!, anchor: CGPoint(x: anchorSprite.position.x, y: self.armRight.frame.maxY))
    self.physicsWorld.add(pinAndRightArmJoint)

    var pinAndLeftArmJoint = SKPhysicsJointPin.joint(withBodyA: anchorSprite.physicsBody!, bodyB: armLeft.physicsBody!, anchor: CGPoint(x: anchorSprite.position.x, y: self.armLeft.frame.maxY))
    self.physicsWorld.add(pinAndLeftArmJoint)

}

Below is an image from running the above code (they are close together).

How can I make sure the lines are always 30˚ apart and maintain 30˚ apart even when rotated?

Answer 1

To keep your two lines separated by exactly 30°, you can use an SKPhysicsJointFixed, which is just what it sounds like: it pins two physicsBodies together in a fixed position. Since you already have them positioned the way you want, just add this code where you have the other SKPhysicsJoints to hold them that way:

let fixArms = SKPhysicsJointFixed.joint(withBodyA: armLeft.physicsBody!, bodyB: armRight.physicsBody!, anchor: CGPoint.zero)
self.physicsWorld.add(fixArms)

Result: