I want to create a line that I can tell it where to start and where to end in a Scene in ARKit. Someone else made this class but I get errors. Something simple like startLine at node... and endLine at node... would be helpful. I feel like it shouldn't be so complicated to do a simple line between two points so if your answer is complicated please explain why it has to be. Thank you all for your help! 

```
class LineNode: SCNNode {

private(set) var cylinder: SCNCylinder
private(set) var positionA: SCNVector3
private(set) var positionB: SCNVector3

init(with startingPoint: SCNVector3, endPoint: SCNVector3, radius: Float = 0.02, color: UIColor = .red) {
    self.positionA = startingPoint
    self.positionB = endPoint
    let vector = endPoint - startingPoint  *//error*
    let height = vector.length()
    cylinder = SCNCylinder(radius: radius, height: Float(height))
    cylinder.radialSegmentCount = 8
    cylinder.firstMaterial?.diffuse.contents = color
    super.init()
    geometry = cylinder
    position = (endPoint + startingPoint) / 2   *//error*
    eulerAngles = SCNVector3.lineEulerAngles(vector: vector)
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
}

```

// I get the error:Binary operator '-' cannot be applied to two 'SCNVector3' operands