title: iPhone opengl es: Conceptual knowledge
body: <p>Hi guys I have a conceptual question in the render function of opengles on the iPhone. Say I have a cube. The cube has 6 faces and consequently 12 triangles. If I calculate a normal for each triangle I have 12 normals, each normal has x,y,z cordinates. Consequently I have an array of 36 floats. In my render function I want to pass the x,y,z cordinates to the vertex for some lighting related calculations.  This is my call to achieve that</p>
  
  <pre><code>  glVertexAttribPointer(_simpleLightNormalAttribute, 3, GL_FLOAT, GL_FALSE, sizeof(float), duplicateNormals); 
  </code></pre>
  
  <p>The indexes 0,1,2 contain the x,y,z cordinates of the first triangle and so on. How does opengl know that indexes 2,3,4 contain the x,y,z cordinates of the 2 triangle?</p>
  
  <p>Any help would be much appreciated/</p>