title: XML3D: generateRay
body: <p>I'm implementing draggable object in XML3D and i need a help with <code>xml3d.generateRay</code> function, as an argument it takes two numbers, as I understand correctly those are x,y coordinates of point in projection space that ray passes through. But are those coordinates in reference to the window element (left-top corner of the browser window) or to the xml upper-left corner?</p>
  
  <p>Second question: how can I get hit point from <code>getElementByRay</code></p>
  
  <p>Specification says differently for different versions - and since there is no spec for 4.9 I ask.</p>