title: glsl double-precision vertex buffer
body: <p>If I create a double-precision vertex buffer, for example:</p>
  
  <pre><code>GLuint vertBuffer, spanBuffer, spanCount, patchSize, program; // already setup
  glUseProgram (program);
  glEnableClientState (GL_VERTEX_ARRAY);
  glBindBuffer (GL_ARRAY_BUFFER, vertBuffer);
  glVertexPointer (3, GL_DOUBLE, 0, 0);
  glPatchParameteri (GL_PATCH_VERTICES, patchSize);
  glBindBuffer (GL_ELEMENT_ARRAY_BUFFER, spanBuffer);
  glDrawElements (GL_PATCHES,  spanCount * patchSize, GL_UNSIGNED_INT, 0);
  </code></pre>
  
  <p>How do I access the double precision data in my vertex shader? Should I be able to do this?</p>
  
  <pre><code>// GLSL VERTEX SHADER
  #version 410
  
  in dvec4 gl_Vertex;
  
  void main ()
  {
  &lt;snip&gt;
  </code></pre>