title: when the CgCompiler compile a cgfx file?
body: <p>Find some code in a cgfx file like:</p>
  <pre><code>technique techname
  {
     pass videoproc
     {
        VertexProgram = compile latest vertex();
        FragmentProgram = compile latest fragment():
     }
  }
  </code></pre>
  <p>is that means before draw the texture, CgCompiler will compile this cgfx file or the function?
  By the way, is there any doc or tutorial for classes in Cg?</p>