How to use pinch gesture in game scene

Question

I need your help guys. I have game scene and func which allow to move camera using panGesture. Also i need pinchGesture to zoom in and out my SKScene. I found some code here, but it lags. Can plz someone help me to improve this code? `

@objc private func didPinch(_ sender: UIPinchGestureRecognizer) {
            guard let camera = self.camera else {return}
            if sender.state == .changed {
                previousCameraScale = camera.xScale
            }
            camera.setScale(previousCameraScale * 1 / sender.scale)
            sender.scale = 1.0
        }

`

Answer 1

try this pinch code.

//pinch -- simple version
@objc func pinch(_ recognizer:UIPinchGestureRecognizer) {
    guard let camera = self.camera else { return } // The camera has a weak reference, so test it
    
    if recognizer.state == .changed {
        let deltaScale = (recognizer.scale - 1.0)*2
        let convertedScale = recognizer.scale - deltaScale
        let newScale = camera.xScale*convertedScale
        camera.setScale(newScale)
        
        //reset value for next time
        recognizer.scale = 1.0
    }
}

although i would recommend this slightly more complicated version which centers the pinch around the touch point. makes for a much nicer pinch in my experience.

//pinch around touch point
@objc func pinch(_ recognizer:UIPinchGestureRecognizer) {
    guard let camera = self.camera else { return } // The camera has a weak reference, so test it

    //cache location prior to scaling
    let locationInView = recognizer.location(in: self.view)
    let location = self.convertPoint(fromView: locationInView)
    
    if recognizer.state == .changed {
        let deltaScale = (recognizer.scale - 1.0)*2
        let convertedScale = recognizer.scale - deltaScale
        let newScale = camera.xScale*convertedScale
        camera.setScale(newScale)
        
        //zoom around touch point rather than center screen
        let locationAfterScale = self.convertPoint(fromView: locationInView)
        let locationDelta = location - locationAfterScale
        let newPoint = camera.position + locationDelta
        camera.position = newPoint
        
        //reset value for next time
        recognizer.scale = 1.0
    }
}

//also need these extensions to add and subtract CGPoints
extension CGPoint { 
  static func + (a:CGPoint, b:CGPoint) -> CGPoint {
      return CGPoint(x: a.x + b.x, y: a.y + b.y)
  }   

  static func - (a:CGPoint, b:CGPoint) -> CGPoint {
      return CGPoint(x: a.x - b.x, y: a.y - b.y)
  }
}