ARKit physics – Why these two objects don't interact with each other? - swift

Question

Why this 2 object pass through each other and not interact, what I'm doing wrong?
on each object I applied the property physicsBody which should allow to the physic engine to work.
I add the square object using a tap gesture, creating the anchor with name "base" and in the render add the object base.
for the ball I use a raycast query to position the ball over the plane.
all working fine, only the dynamic looks wrong, they pass each other.
// my square base
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
if let nome = anchor.name, nome == "base" {
let geometry = SCNPlane(width: 1, height: 1)
let material = SCNMaterial()
material.diffuse.contents = UIColor(red: 90/255, green: 200/255, blue: 250/255, alpha: 0.50)
geometry.materials = [material]
// physics
let physSchape = SCNPhysicsShape(geometry: geometry, options: nil)
let planePhysic = SCNPhysicsBody(type: .static, shape: physSchape)
planePhysic.restitution = 0.0
planePhysic.friction = 1.0
let nodo = SCNNode(geometry: geometry)
nodo.eulerAngles.x = -.pi / 2
nodo.physicsBody = planePhysic
node.addChildNode(nodo)
}
}
and this ball:
func addBall(recognizer: UITapGestureRecognizer){
let tapLocation = recognizer.location(in: view)
guard let query = view.raycastQuery(from: tapLocation, allowing: .existingPlaneGeometry, alignment: .horizontal) else {return}
// ottengo posizione real world
guard let translation = view.castRay(for: query).first?.worldTransform.translation else {return}
let x = translation.x
let y = translation.y
let z = translation.z
let ballGeometry = SCNSphere(radius: 0.1)
let mat = SCNMaterial()
mat.diffuse.contents = UIImage(named: "ball")
ballGeometry.materials = [mat]
//Physics
let physSchape = SCNPhysicsShape(geometry: ballGeometry, options: nil)
let ballPhysic = SCNPhysicsBody(type: .dynamic, shape: physSchape)
ballPhysic.mass = 0.2
ballPhysic.friction = 0.8
let nodeBall = SCNNode(geometry: ballGeometry)
nodeBall.position = SCNVector3(x,y+0.3,z)
nodeBall.physicsBody = ballPhysic
view.scene.rootNode.addChildNode(nodeBall)
}
they should interact each other , but actually my ball pass through the base.

Answer 1

If you're trying to simulate two objects' collision, first of all, you must implement the protocol called SCNPhysicsContactDelegate and its delegate:
weak var contactDelegate: SCNPhysicsContactDelegate? { get set }
for using its three optional instance methods:
func physicsWorld(_ world: SCNPhysicsWorld, didBegin contact: SCNPhysicsContact)
func physicsWorld(_ world: SCNPhysicsWorld, didUpdate contact: SCNPhysicsContact)
func physicsWorld(_ world: SCNPhysicsWorld, didEnd contact: SCNPhysicsContact)
And, of course, category bit mask and collision bit mask are required.
If you need a more detailed info, please look at THIS POST.