scenekit edit model

 // add a tap gesture recognizer
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleTap(_:)))
        scnView.addGestureRecognizer(tapGesture)`

func handleTap(gestureRecognize: UIGestureRecognizer) {
        // retrieve the SCNView
        let scnView = self.view as! SCNView
        
        // check what nodes are tapped
        let p = gestureRecognize.locationInView(scnView)
        let hitResults = scnView.hitTest(p, options: nil)
        // check that we clicked on at least one object
        if hitResults.count > 0 {
            // retrieved the first clicked object
            let result: AnyObject! = hitResults[0]
            
            // get its material
            let material = result.node!.geometry!.firstMaterial!
            
            
            // highlight it
            SCNTransaction.begin()
            SCNTransaction.setAnimationDuration(0.5)
            
            // on completion - unhighlight
            SCNTransaction.setCompletionBlock {
                SCNTransaction.begin()
                SCNTransaction.setAnimationDuration(0.5)
                
                material.emission.contents = UIColor.blackColor()
                
                SCNTransaction.commit()
            }
            
            material.emission.contents = UIColor.redColor()
            
            SCNTransaction.commit()
        }
    }