title: Controlling depth buffer and drawing order in OpenSceneGraph
body: <p>I'm working on a little GIS app using OSG, but i'm quite a newbie with it.</p>
  
  <p>As the view is not changing a lot, i'm not struggling to keep a decent fps ratio. </p>
  
  <p>I have to draw multiple layers on the same view. Layers may overlaps, but not always.</p>
  
  <p>Right now, to be able to choose which layer is on top of the others, i'm using the PolygonOffet properties, but I don't like it.</p>
  
  <p>Here is what I want to try :
  -put a clear node on my root to clear all the buffers
  -put a clear node on top of each layer node to clear only the depth buffer
  -find a way to force OSG to draw those layer in a specific order</p>
  
  <p>So my question is :
  - Is it possible ? 
  - How can I choose the rendering order of my layer's node ? </p>