Collision between two nodes not detected ARKit - swift

Question

I created two nodes: a sphere and a box:
var sphere = SCNNode(geometry: SCNSphere(radius: 0.005))
//I get the box node from scn file
let boxScene = SCNScene(named: "art.scnassets/world.scn")!
var boxNode: SCNNode?
I want two nodes or physicsBody's to interact, so I created a category for categoryBitMask and contactTestBitMask:
struct CollisionCategory: OptionSet {
let rawValue: Int
static let box = CollisionCategory(rawValue: 1)
static let sphere = CollisionCategory(rawValue: 2)
}
Here I set the box node as a physics body:
self.boxScene.rootNode.enumerateChildNodes { (node, _) in
if node.name == "box" {
boxNode = node
let boxBodyShape = SCNPhysicsShape(geometry: SCNBox(width: 0.1, height: 0.1, length: 0.1, chamferRadius: 0.1), options: nil)
let physicsBody = SCNPhysicsBody(type: .static, shape: boxBodyShape)
boxNode!.physicsBody = physicsBody
boxNode!.physicsBody?.categoryBitMask = CollisionCategory.box.rawValue
boxNode!.physicsBody?.contactTestBitMask = CollisionCategory.sphere.rawValue
boxNode!.physicsBody?.collisionBitMask = boxNode!.physicsBody!.contactTestBitMask
}
}
Here I set the sphere node in the render function, which you can move around the view:
func setUpSphere() {
let sphereBodySphere = SCNPhysicsShape(geometry: SCNSphere(radius: 0.005))
let physicsBody = SCNPhysicsBody(type: .kinematic, shape: sphereBodySphere)
sphere.physicsBody = physicsBody
sphere.physicsBody?.categoryBitMask = CollisionCategory.sphere.rawValue
sphere.physicsBody?.contactTestBitMask = CollisionCategory.box.rawValue
sphere.geometry?.firstMaterial?.diffuse.contents = UIColor.blue
sphere.physicsBody?.collisionBitMask = sphere.physicsBody!.contactTestBitMask
previousPoint = currentPosition
}
///It Adds a sphere and changes his position
func renderer(_ renderer: SCNSceneRenderer, willRenderScene scene: SCNScene, atTime time: TimeInterval) {
guard let pointOfView = sceneView.pointOfView else { return }
let mat = pointOfView.transform
let dir = SCNVector3(-1 * mat.m31, -1 * mat.m32, -1 * mat.m33)
let currentPosition = pointOfView.position + (dir * 0.185)
if buttonPressed {
if let previousPoint = previousPoint {
sphere.position = currentPosition
sceneView.scene.rootNode.addChildNode(sphere)
}
}
}
I added the protocol SCNPhysicsContactDelegate to the ViewController,
and I set in ViewDidLoad():
override func viewDidLoad() {
super.viewDidLoad()
sceneView.delegate = self
sceneView.scene.physicsWorld.contactDelegate = self
///I correctly see the shapes of the sphere and the box physics bodies using
sceneView.debugOptions = .showPhysicsShapes
createBox()
setUpSphere()
sceneView.scene = boxScene
sceneView.scene.physicsWorld.contactDelegate = self
}
Then I added that function:
func physicsWorld(_ world: SCNPhysicsWorld, didEnd contact: SCNPhysicsContact) {
print("Collision!")
}
This is what happens.
When the two nodes collide nothing happens, so I can't know if the two bodies are touching. Could the problem be about .kinematic, .static or about the function render()?
I followed step by step different tutorials about collisions in ARKit: Tutorial 1, Tutorial 2.
I have no idea why it doesn't work like expected.
Is there something wrong in my code?
Download file code link: https://ufile.io/20sla

Answer 1

willRenderScene is called uptown 60 times a second for every time the scene is going to be rendered. Since you're recreating the physics body every time it's probably messing up the physics engine determine collisions.
Try changing your code to only create the physics body once during setup.