make SKPhysicsBody unidirectional

Question

I have a SKSpriteNode as a ball, it's been given all the SKPhysicsBody properties move around in all direction. What I want now is to make it unidirectional (only move in that direction it hasn't move to before and not go back in to a path it had move upon). Currently I have following thoughts on this the problem,

make a fieldBitMask, to the path that is iterated by it and repel the ball to not go back
apply some kind of force/ impulses on the ball from touchesBegan/ touchesMoved method to keep it from going back
something that can be handled in update method
a lifesaver from stackflowoverflow, who is coding even on the weekend :)

Supporting Code snippets for better understanding,

//getting current touch position by using UIEvent methods
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touch = touches.first else {return}
        let location = touch.location(in: self)
        lastTouchPoint = location
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touch = touches.first else {return}
        let location = touch.location(in: self)
        lastTouchPoint = location
    }
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        lastTouchPoint = nil
    }
    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        lastTouchPoint = nil
    }

//ball created
    func createPlayer(){
        player = SKSpriteNode(imageNamed: "player")
        player.position = CGPoint(x: 220, y: 420)
        player.zPosition = 1

    //physics for ball
    player.physicsBody = SKPhysicsBody(circleOfRadius: player.size.width / 2)
    player.physicsBody?.allowsRotation = false
    player.physicsBody?.linearDamping =  0.5


    player.physicsBody?.categoryBitMask = collisionTypes.player.rawValue
    player.physicsBody?.contactTestBitMask = collisionTypes.finish.rawValue
    player.physicsBody?.collisionBitMask = collisionTypes.wall.rawValue

    addChild(player)
}

//unwarp the optional property, calclulate the postion between player touch and current ball position
override func update(_ currentTime: TimeInterval) {
    guard isGameOver == false else { return }
    if let lastTouchPosition = lastTouchPoint {
        //this usually gives a large value (related to screen size of the device) so /100 to normalize it
        let diff = CGPoint(x: lastTouchPosition.x - player.position.x, y: lastTouchPosition.y - player.position.y)
        physicsWorld.gravity = CGVector(dx: diff.x/100, dy: diff.y/100)
    }
}

i'm due to submit this tomorrow, any help is appreciated ;( – Frostmourne Feb 02 '20 at 09:55 — Frostmourne, Feb 02 '20 at 09:55

score 0 · Accepted Answer · answered Feb 06 '20 at 08:55

Well it was a combination little hacks in touchesBegan/ touchesMoved and update func,

First you need to catch on which touch occurred, get it's name (in my case I made nodes which had alpha of 0, but become visible upon moving over them i.e alpha 1). In touchesBegan, touchesMoved as follow

                        guard let touch = touches.first else {return}
                        let location = touch.location(in: self)
                        lastTouchPoint = location

                        let positionInScene = touch.location(in: self)
                        let touchedNode = self.atPoint(positionInScene)

                        if let name = touchedNode.name
                        {
                            if name == "vortex"
                            {
                                touching = false
                                self.view!.isUserInteractionEnabled = false
                                print("Touched on the interacted node")
                            }else{
                                self.view!.isUserInteractionEnabled = true
                                touching = true
                            }
                        }
                    }

Second use a BOOL touching to track user interactions, on the screen by using getting a tap recogniser setup, as follow

func setupTapDetection() {
        let t = UITapGestureRecognizer(target: self, action: #selector(tapped(_:)))
        view?.addGestureRecognizer(t)
    }

@objc func tapped(_ tap: UITapGestureRecognizer) {
        touching = true
    }

Finally in update put checks as follow,

        guard isGameOver == false else { return }
        self.view!.isUserInteractionEnabled = true

        if(touching ?? true){
            if let lastTouchPosition = lastTouchPoint {
                //this usually gives a large value (related to screen size of the device) so /100 to normalize it
                let diff = CGPoint(x: lastTouchPosition.x - player.position.x, y: lastTouchPosition.y - player.position.y)
                physicsWorld.gravity = CGVector(dx: diff.x/100, dy: diff.y/100)
            }
        }
    }

make SKPhysicsBody unidirectional

1 Answers1