ARKit and .dae file , strange space between object - swift

Question

on my study project using ARKit and sceneKit I'm facing a strange behaviour when using .dae file.
i have created 2 object a cube and a plane with the following methods (both have physics):
func loadBox() {
let ballGeometry = SCNBox(width: 0.2, height: 0.2, length: 0.2, chamferRadius: 0.02)
let mat = SCNMaterial()
mat.diffuse.contents = UIImage(named: "ball")
ballGeometry.materials = [mat]
//Physic
let physSchape = SCNPhysicsShape(geometry: ballGeometry, options: nil)
let ballPhysic = SCNPhysicsBody(type: .dynamic, shape: physSchape)
ballPhysic.mass = 100
ballPhysic.friction = 0.8
ballPhysic.isAffectedByGravity = true
let nodeBall = SCNNode(geometry: ballGeometry)
nodeBall.name = "ball"
nodeBall.physicsBody = ballPhysic
box = nodeBall
}
func loadPlane(){
let geometry = SCNPlane(width: 1, height: 1)
let material = SCNMaterial()
material.diffuse.contents = UIImage(named: "texture")
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
planePhysic.isAffectedByGravity = true
let nodo = SCNNode(geometry: geometry)
nodo.eulerAngles.x = -.pi / 2
nodo.physicsBody = planePhysic
plane = nodo
}
when I place the box over the plane in the scene they are correctly positioned and touching each other as you can see from the following picture:
Here the problem:
if i use a model downloaded from internet as .dae file of the plane, when insert it in the scene it create a strange space between the box and the plane (see picture)
method I use to load the scn file.
// load the elicopterBase
func loadElicopterBase(){
guard let scene = SCNScene(named: "Model.scnassets/base.scn") else {fatalError()}
guard let nodo = scene.rootNode.childNode(withName: "Plane", recursively: true) else {fatalError()}
// physics
let physSchape = SCNPhysicsShape(node: nodo, options: nil)
let planePhysic = SCNPhysicsBody(type: .static, shape: physSchape)
planePhysic.restitution = 0.0
planePhysic.friction = 1.0
planePhysic.isAffectedByGravity = true
nodo.physicsBody = planePhysic
nodo.name = "base"
DispatchQueue.main.async {
self.eliporto = nodo
}
}
Look like the .dae file have some sort of invisible boundingBox around it.
What or where I can look to find a solution to this.
here some picture of the .dae file in Xcode

Answer 1

Make your floor plane of type "concavePolyhedron" like so:
let body = SCNPhysicsBody(type: .static, shape: SCNPhysicsShape(geometry: yourGeometry, options: [SCNPhysicsShape.Option.type: SCNPhysicsShape.ShapeType.concavePolyhedron]))