A playground experiment using SceneKit in iOS 8 SDK that shows a plane, a torus and a light attached to it casting shadows

plane_torus_light.playground

import UIKit
import SceneKit
import QuartzCore
import XCPlayground

var sceneView = SCNView(frame: CGRect(x: 0, y: 0, width: 350, height: 450))
var scene = SCNScene()
sceneView.scene = scene

XCPShowView("View", sceneView)
sceneView.allowsCameraControl = true

var camera1 = SCNCamera()
var camera1Node = SCNNode()
camera1Node.camera = camera1
camera1Node.position = SCNVector3(x: 0, y: 0, z: 5)
scene.rootNode.addChildNode(camera1Node)

var light1 = SCNLight()
light1.type = SCNLightTypeSpot
light1.castsShadow = true
light1.color = UIColor.whiteColor()

var light1Node = SCNNode()
light1Node.light = light1
light1Node.position = SCNVector3(x: 4, y: 5, z: 3)
scene.rootNode.addChildNode(light1Node)

var torus = SCNTorus(ringRadius: 1, pipeRadius: 0.25)
var torusNode = SCNNode(geometry: torus)

let lookAt = SCNLookAtConstraint(target: torusNode)
light1Node.constraints = [lookAt]

scene.rootNode.addChildNode(torusNode)
torus.firstMaterial?.diffuse.contents = UIColor.whiteColor()
torus.firstMaterial?.specular.contents = UIColor.whiteColor()

var plane = SCNPlane(width: 5.0, height: 5.0)
var planeNode = SCNNode(geometry: plane)

scene.rootNode.addChildNode(planeNode)
plane.firstMaterial?.diffuse.contents = UIColor.whiteColor()
plane.firstMaterial?.specular.contents = UIColor.whiteColor()

Updated version

import UIKit
import SceneKit
import QuartzCore
import XCPlayground
import PlaygroundSupport

var sceneView = SCNView(frame: CGRect(x: 0, y: 0, width: 350, height: 450))
var scene = SCNScene()
sceneView.scene = scene

PlaygroundPage.current.liveView = sceneView
//XCPShowView(identifier: "View", view: sceneView)
sceneView.allowsCameraControl = true

var camera1 = SCNCamera()
var camera1Node = SCNNode()
camera1Node.camera = camera1
camera1Node.position = SCNVector3(x: 0, y: 0, z: 5)
scene.rootNode.addChildNode(camera1Node)

var light1 = SCNLight()
light1.type = SCNLight.LightType.spot
light1.castsShadow = true
light1.color = UIColor.white

var light1Node = SCNNode()
light1Node.light = light1
light1Node.position = SCNVector3(x: 4, y: 5, z: 3)
scene.rootNode.addChildNode(light1Node)

var torus = SCNTorus(ringRadius: 1, pipeRadius: 0.25)
var torusNode = SCNNode(geometry: torus)

let lookAt = SCNLookAtConstraint(target: torusNode)
light1Node.constraints = [lookAt]

scene.rootNode.addChildNode(torusNode)
torus.firstMaterial?.diffuse.contents = UIColor.white
torus.firstMaterial?.specular.contents = UIColor.white

var plane = SCNPlane(width: 5.0, height: 5.0)
var planeNode = SCNNode(geometry: plane)

scene.rootNode.addChildNode(planeNode)
plane.firstMaterial?.diffuse.contents = UIColor.white
plane.firstMaterial?.specular.contents = UIColor.white