SceneKit Physics Test

GameViewController.swift

import SceneKit
import QuartzCore

class GameViewController: NSViewController {
    
    @IBOutlet weak var gameView: GameView!
    
    override func awakeFromNib(){
        
        let numBox = 300
        let camDistance:CGFloat = 55.0
        
        // Create a new scene
        let scene = SCNScene()
        
        // Create and add a camera t the scene
        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        
        scene.rootNode.addChildNode(cameraNode)

        cameraNode.position = SCNVector3(x: 0, y: 15.0, z: camDistance)
        
        // Make floor node
        let floorNode = SCNNode()
        
        let floor = SCNFloor()
        floor.reflectivity = 0.25
        floorNode.geometry = floor

        // Floor Physics
        let floorShape = SCNPhysicsShape(geometry: floor, options: nil)
        let floorBody = SCNPhysicsBody(type: .Static, shape: floorShape)
        
        floorNode.physicsBody = floorBody;
        
        scene.rootNode.addChildNode(floorNode)
        
        // Add box nodes to the scene
        for x in 0..<numBox {
            let node = SCNNode()
            let rdx = randomCGFloat() * camDistance - camDistance / 2
            let rdy = randomCGFloat() * 300
            let rdz = randomCGFloat() * camDistance - camDistance / 2
            node.position = SCNVector3Make(rdx, rdy, rdz)
            let box = SCNBox(width: randomCGFloat() * 5.0, height: randomCGFloat() * 5.0, length: randomCGFloat() * 5.0, chamferRadius: 0.0)
            node.geometry = box
            
            // Create and configure a material
            let material = SCNMaterial()
            material.specular.contents = NSColor.blueColor()
            material.locksAmbientWithDiffuse = true
            
            // Set shaderModifiers properties
            let snipet = "uniform float Scale = 3.0;\n" +
                "uniform float Width = 0.5;\n" +
                "uniform float Blend = 0.0;\n" +
                "vec2 position = fract(_surface.diffuseTexcoord * Scale);" +
                "float f1 = clamp(position.y / Blend, 0.0, 1.0);" +
                "float f2 = clamp((position.y - Width) / Blend, 0.0, 1.0);" +
                "f1 = f1 * (1.0 - f2);" +
                "f1 = f1 * f1 * 2.0 * (3. * 2. * f1);" +
                "_surface.diffuse = mix(vec4(1.0), vec4(0.0), f1);"
            
            material.shaderModifiers = [SCNShaderModifierEntryPointSurface: snipet]
            
            // Set the material to the 3D object geometry
            node.geometry?.firstMaterial = material
            
            let boxShape = SCNPhysicsShape(geometry: box, options: nil)
            let boxBody = SCNPhysicsBody(type: .Dynamic, shape: boxShape)
            
            node.physicsBody = boxBody;
            scene.rootNode.addChildNode(node)
        }
        
        // Set the scene to the view
        self.gameView!.scene = scene
        
        // Allows the user to manipulate the camera
        self.gameView!.allowsCameraControl = true
        
        // Show statistics such as fps and timing information
        self.gameView!.showsStatistics = true
        
        // Configure the view
        self.gameView!.backgroundColor = NSColor.blackColor()
    }
    
    func randomCGFloat() -> CGFloat {
        return CGFloat(arc4random()) /  CGFloat(UInt32.max)
    }
    
}

Hey i have a 3d collada object how can i apply physics on it in scenekit??