// Create a sphere at (0,0,0) and apply a diffuse green color to it
@IBAction func startMappingAndRenderSphere(_ sender: Any) {
// start placenote mapping
LibPlacenote.instance.startSession()
// render a sphere at (0,0,0)
let geometry:SCNGeometry = SCNSphere(radius: 0.05) //units, meters
let geometryNode = SCNNode(geometry: geometry)
geometryNode.position = SCNVector3(x:0.0, y:0.0, z:0.0)
geometryNode.geometry?.firstMaterial?.diffuse.contents = UIColor.green
sceneView.scene.rootNode.addChildNode(geometryNode)