title: Fixed pipeline to glsl gl_Normal / vnormal / v_normal
body: <p>The more I read the more confused I become. I am trying to learn getting from old <code>opengl1</code> fixed pipeline to modern gl. I learned a lot already but for one thing I am still unsure about. In old tutorials its just used as <code>gl_Normal</code>, in newer its often referred to <code>vnormal</code> or <code>v_normal</code>.</p>
  
  <p>In older versions I didn't have to take care about that, also in fixed pipeline it seems to be provided automatically. So where to get this or rather, how to calculate it? Must it be done in c++ or can it be done in vertex or fragment shader as well from vert position (in old tutorials referred as <code>gl_Vertex</code>)?</p>
  
  <p>A sample or pseudo code would be nice.</p>