title: Using SceneKit for hitTesting not returning a hit with SCNNode
body: <p>The documentation in XCode clearly states that hitTesting a geometry in SceneKit can be done with SCNRender, SCNView or the SCNNode themselves when one plans to test a 3D line segment.  I have a use for SCNScene with its nodes without a renderer or a view, therefore I am planning to use SCNNode hitTesting.  I  create a SCNScene, put a SCNNode in it and test a simple ray that goes through, but I always get an empty hitList and I don't understand why:</p>
  
  <pre><code>import Swift
  import SceneKit
  
  let boxGeometry = SCNBox(width: 1.0, height: 1.0, length: 1.0, chamferRadius: 0)
  let boxNode = SCNNode(geometry: boxGeometry)
  
  var scene = SCNScene()
  scene.rootNode.addChildNode(boxNode)
  
  let from = SCNVector3(x: 0, y: -2, z: 0)
  let to = SCNVector3(x: 0, y: 2 , z: 0)
  
  var hits = scene.rootNode.hitTestWithSegmentFromPoint(from, toPoint: to, options:nil) // this is always empty
  if hits != nil {
      if hits!.count &gt; 0 {
          var hit = (hits!.first as! SCNHitTestResult).node as SCNNode
      }
  }
  </code></pre>
  
  <p>I have tried passing various forms of options but nothing changes.</p>
  
  <ol>
  <li>SCNHitTestFirstFoundOnlyKey: yes or no does not change anything</li>
  <li>SCNHitTestSortResultsKey:  yes or no does not change anything </li>
  <li>SCNHitTestClipToZRangeKey: invalid for SCNNode</li>
  <li>SCNHitTestBackFaceCullingKey: yes or no does not change anything </li>
  <li>SCNHitTestBoundingBoxOnlyKey: yes or no does not change anything </li>
  <li>SCNHitTestRootNodeKey: rootNOde of scene or boxNode does not change
  anything </li>
  <li>SCNHitTestIgnoreHiddenNodesKey: yes or no does not change anything </li>
  </ol>
  
  <p>What am I doing wrong?</p>