Issue with adding node to scene view - swift

Question

I am having an issue with the way the model is being placed on the scene view.
The problem is that the model downloads successfully but for some reason it appears on top of the scene view.
here is a video of the problem:
https://www.youtube.com/watch?v=-pTPEZTF9zo
view did load:
override func viewDidLoad() {
super.viewDidLoad()
self.dowloadModel()
self.sceneView.debugOptions = [ARSCNDebugOptions.showWorldOrigin, ARSCNDebugOptions.showFeaturePoints]
self.configuration.planeDetection = .horizontal
self.sceneView.session.run(configuration)
self.registerGestureRecogniser()
}
Gesture recofniser:
func registerGestureRecogniser(){
let tapGestureRecogiser = UITapGestureRecognizer(target: self, action: #selector(tapped))
self.sceneView.addGestureRecognizer(tapGestureRecogiser)
}
Tapped function:
#objc func tapped(sender:UITapGestureRecognizer){
let sceneView = sender.view as! ARSCNView
let tapLocation = sender.location(in: sceneView)
let hitTest = sceneView.hitTest(tapLocation, types: .existingPlaneUsingExtent)
if !hitTest.isEmpty{
print("touched a horizontal surface")
self.addItem2(hitTestResult: hitTest.first!)
}
else{
print("no match")
}
}
Download model from AWS:
private func dowloadModel(){
let url = URL(string: "https://ENTER URL HERE")!
URLSession.shared.dataTask(with: url) { data, response, error in
if let error = error{
print(error.localizedDescription)
return
}
if let data = data{
print(data)
let documentDirectories = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
if let documentDirectory = documentDirectories.first{
let fileURL = documentDirectory.appendingPathComponent("Food.scn")
let dataNS : NSData? = data as NSData
try! dataNS?.write(to: fileURL, options: .atomic)
print("Saved!")
}
}
}.resume()
}
Add Item 2 function:
func addItem2(hitTestResult : ARHitTestResult){
let documentDirectories = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
if let documentDirectory = documentDirectories.first{
let fileURL = documentDirectory.appendingPathComponent("Food.scn")
do{
let scene = try SCNScene(url: fileURL, options: nil)
let node = scene.rootNode.childNode(withName: "Burger", recursively: true)!
let material = SCNMaterial()
material.diffuse.contents = UIImage(named: "Hamburger_BaseColor")
material.diffuse.wrapT = SCNWrapMode.repeat
material.diffuse.wrapS = SCNWrapMode.repeat
material.isDoubleSided = true
let transform = hitTestResult.worldTransform
let thirdColumn = transform.columns.3
node.position = SCNVector3(thirdColumn.x, thirdColumn.y, thirdColumn.z)
self.sceneView.scene.rootNode.addChildNode(node)
}
catch{
print(error)
}
}
}

Answer 1

It seems that this issue entirely depends on a pivot point's position and a scale of your model.
Pivot point meets ARAnchor and helps you control a model's offset, orientation and scale of model on a floor, a table-top, or a wall.
node.scale = SCNVector3(x: 0.2, y: 0.2, z: 0.2)
node.pivot = SCNMatrix4MakeTranslation(0, -0.5, 0)
...or for positioning pivot use this approach:
node.simdPivot.columns.3.y = -0.5
So if you want your model to precisely stand on an invisible detected plane move a pivot point in SceneKit toward desired place or set its position in 3D authoring tool (like 3dsMax or Blender).