Why is SCNNode "jiggling" when dropped onto SCNPlane? - ios

Question

I have a SCNPlane that is added to the scene when a sufficient area is detected for a horizontal surface. The plane appears to be placed in a correct spot, according to the floor/table it's being placed on. The problem is when I drop a SCNNode(this has been consistent whether it was a box, pyramid, 3D-model, etc.) onto the plane, it will eventually find a spot to land and 99% start jiggling all crazy. Very few times has it just landed and not moved at all. I also think this may be cause by the node being dropped and landing slightly below the plane surface. It is not "on top" neither "below" the plane. Maybe the node is freaking out because it's kind of teetering between both levels?
Here is a video of what's going on, you can see at the beginning that the box is below and above the plane and the orange box does stop when it collides with the dark blue box, but does go back to its jiggling ways when the green box collides with it at the end:
The code is here on github
I will also show some of the relevant parts embedded in code:
I just create a Plane class to add to the scene when I need to
class Plane: SCNNode {
var anchor :ARPlaneAnchor
var planeGeometry :SCNPlane!
init(anchor :ARPlaneAnchor) {
self.anchor = anchor
super.init()
setup()
}
func update(anchor: ARPlaneAnchor) {
self.planeGeometry.width = CGFloat(anchor.extent.x)
self.planeGeometry.height = CGFloat(anchor.extent.z)
self.position = SCNVector3Make(anchor.center.x, 0, anchor.center.z)
let planeNode = self.childNodes.first!
planeNode.physicsBody = SCNPhysicsBody(type: .static, shape: SCNPhysicsShape(geometry: self.planeGeometry, options: nil))
}
private func setup() {
//plane dimensions
self.planeGeometry = SCNPlane(width: CGFloat(self.anchor.extent.x), height: CGFloat(self.anchor.extent.z))
//plane material
let material = SCNMaterial()
material.diffuse.contents = UIImage(named: "tronGrid.png")
self.planeGeometry.materials = [material]
//plane geometry and physics
let planeNode = SCNNode(geometry: self.planeGeometry)
planeNode.physicsBody = SCNPhysicsBody(type: .static, shape: SCNPhysicsShape(geometry: self.planeGeometry, options: nil))
planeNode.physicsBody?.categoryBitMask = BodyType.plane.rawValue
planeNode.position = SCNVector3Make(anchor.center.x, 0, anchor.center.z)
planeNode.transform = SCNMatrix4MakeRotation(Float(-Double.pi / 2.0), 1, 0, 0)
//add plane node
self.addChildNode(planeNode)
}
This is the ViewController
enum BodyType: Int {
case box = 1
case pyramid = 2
case plane = 3
}
class ViewController: UIViewController, ARSCNViewDelegate, SCNPhysicsContactDelegate {
//outlets
#IBOutlet var sceneView: ARSCNView!
//globals
var planes = [Plane]()
var boxes = [SCNNode]()
//life cycle
override func viewDidLoad() {
super.viewDidLoad()
//set sceneView's frame
self.sceneView = ARSCNView(frame: self.view.frame)
//add debugging option for sceneView (show x, y , z coords)
self.sceneView.debugOptions = [ARSCNDebugOptions.showFeaturePoints, ARSCNDebugOptions.showWorldOrigin]
//give lighting to the scene
self.sceneView.autoenablesDefaultLighting = true
//add subview to scene
self.view.addSubview(self.sceneView)
// Set the view's delegate
sceneView.delegate = self
//subscribe to physics contact delegate
self.sceneView.scene.physicsWorld.contactDelegate = self
//show statistics such as fps and timing information
sceneView.showsStatistics = true
//create new scene
let scene = SCNScene()
//set scene to view
sceneView.scene = scene
//setup recognizer to add scooter to scene
let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(tapped))
sceneView.addGestureRecognizer(tapGestureRecognizer)
}
//MARK: helper funcs
#objc func tapped(recognizer: UIGestureRecognizer) {
let scnView = recognizer.view as! ARSCNView
let touchLocation = recognizer.location(in: scnView)
let touch = scnView.hitTest(touchLocation, types: .existingPlaneUsingExtent)
//take action if user touches box
if !touch.isEmpty {
guard let hitResult = touch.first else { return }
addBox(hitResult: hitResult)
}
}
private func addBox(hitResult: ARHitTestResult) {
let boxGeometry = SCNBox(width: 0.1,
height: 0.1,
length: 0.1,
chamferRadius: 0)
let material = SCNMaterial()
material.diffuse.contents = UIColor(red: .random(),
green: .random(),
blue: .random(),
alpha: 1.0)
boxGeometry.materials = [material]
let boxNode = SCNNode(geometry: boxGeometry)
//adding physics body, a box already has a shape, so nil is fine
boxNode.physicsBody = SCNPhysicsBody(type: .dynamic, shape: nil)
//set bitMask on boxNode, enabling objects with diff categoryBitMasks to collide w/ each other
boxNode.physicsBody?.categoryBitMask = BodyType.plane.rawValue | BodyType.box.rawValue
boxNode.position = SCNVector3(hitResult.worldTransform.columns.3.x,
hitResult.worldTransform.columns.3.y + 0.3,
hitResult.worldTransform.columns.3.z)
self.sceneView.scene.rootNode.addChildNode(boxNode)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
let configuration = ARWorldTrackingConfiguration()
configuration.planeDetection = .horizontal
//track objects in ARWorld and start session
sceneView.session.run(configuration)
}
//MARK: - ARSCNViewDelegate
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
//if no anchor found, don't render anything!
if !(anchor is ARPlaneAnchor) {
return
}
DispatchQueue.main.async {
//add plane to scene
let plane = Plane(anchor: anchor as! ARPlaneAnchor)
self.planes.append(plane)
node.addChildNode(plane)
//add initial scene object
let pyramidGeometry = SCNPyramid(width: CGFloat(plane.planeGeometry.width / 8), height: plane.planeGeometry.height / 8, length: plane.planeGeometry.height / 8)
pyramidGeometry.firstMaterial?.diffuse.contents = UIColor.white
let pyramidNode = SCNNode(geometry: pyramidGeometry)
pyramidNode.name = "pyramid"
pyramidNode.physicsBody = SCNPhysicsBody(type: .dynamic, shape: nil)
pyramidNode.physicsBody?.categoryBitMask = BodyType.pyramid.rawValue | BodyType.plane.rawValue
pyramidNode.physicsBody?.contactTestBitMask = BodyType.box.rawValue
pyramidNode.position = SCNVector3(-(plane.planeGeometry.width) / 3, 0, plane.planeGeometry.height / 3)
node.addChildNode(pyramidNode)
}
}
func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
let plane = self.planes.filter {
plane in return plane.anchor.identifier == anchor.identifier
}.first
if plane == nil {
return
}
plane?.update(anchor: anchor as! ARPlaneAnchor)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
//pause session
sceneView.session.pause()
}
}

Answer 1

I think i followed the same tutorial. I also had same result. Reason is because when the cube drops from higher place, it accelerates and doesnot exactly hit on the plane but passes through. If you scale down the cube to '1 mm' you can see box completely passes through plane and continue falling below plane. You can try droping cube from nearer to the plane, box drops slower and this 'jiggling' will not occur. Or you can try with box with small height instead of plane.

Answer 2

I had the same problem i found out one solution.I was initializing the ARSCNView programmatically.I just removed those code and just added a ARSCNView in the storyboard joined it in my UIViewcontroller class using IBOutlet it worked like a charm.
Hope it helps anyone who is going through this problem.
The same code is below.
#IBOutlet var sceneView: ARSCNView!
override func viewDidLoad() {
super.viewDidLoad()
self.sceneView.debugOptions = [ARSCNDebugOptions.showFeaturePoints,ARSCNDebugOptions.showWorldOrigin]
sceneView.delegate = self
sceneView.showsStatistics = true
let scene = SCNScene()
sceneView.scene = scene
}

Answer 3

The "jiggling" is probably caused by an incorrect gravity vector. Try experimenting with setting the gravity of your scene.
For example, add this to your viewDidLoad function:
sceneView.scene.physicsWorld.gravity = SCNVector3Make(0.0, -1.0, 0.0)
I found that setting the gravity - either through code, or by loading an empty scene - resolves this issue.