I'm trying to use glDrawElements() to draw geometry from an obj file. I've created separate arrays for vertex,normal and texture coords and have a index array. The problem i'm running into is that a typical obj file has separate indexes for each data type. Opengl on the other hand only uses one index to traverse all three arrays. In order for glDrawElements() to work these separate arrays must be parallel to each other. so a line for a Quad face in a .obj file that reads:

f 1/1/1 2/2/2 3/3/3 4/4/4

is fine. but a line that reads:

f 7/8/13 9/12/14 10/11/15 8/8/16

won't work since the data isn't parallel.  if opengl only uses one index to traverse the three arrays then the size of the three arrays has to match also.  for example if i'm drawing a simple cube using an indexed array:

Total number of vertices = 8
Total number of normals = 24
Total number of Texture coord = 14

after reorganizing the data so that the three arrays match in size and order the number of vertices goes from 8 to 24, not a big deal for a cube but if i'm dealing with 500,000 polys... well you get the idea. why even bother using an indexed array?