title: Right model of texture coordinates in OpenGL ES
body: <p>I have a trouble with understanding mapping of texture in OpenGL ES. For example, i have a little obj-file containing information like this:</p>
  
  <ol>
  <li>v -75 75 -50</li>
  <li>v 75 75 -50</li>
  <li>v -75 -75 -50</li>
  <li><p>v 75 -75 -50</p></li>
  <li><p>vt 0 0</p></li>
  <li>vt 0 1</li>
  <li>vt 1 1</li>
  <li><p>vt 1 0</p></li>
  <li><p>f 4/3 3/2 1/1</p></li>
  <li>f 2/4 4/3 1/1</li>
  </ol>
  
  <p>If I use this vts then texture isn't mapping correctly. But If I switch vts like this:</p>
  
  <ol>
  <li>vt 1 0 </li>
  <li>vt 0 1 </li>
  <li>vt 1 1 </li>
  <li>vt 0 0</li>
  </ol>
  
  <p>all start working fine. 
  I tryed to draw this coordinates just to get visual representation of them and get image like this (I inverted y-axis coordinates). 
   <a href="http://imgur.com/BRQgKay" rel="nofollow">http://imgur.com/BRQgKay</a>
  In first case I see good representation, but it doesn't work, heh. In second case, I see something horrible, but it work.
  Why it works, I completely cannot understand. 
  Any ideas?
  Thanks for any help.
  EDIT:
  <a href="http://i.stack.imgur.com/4YdpM.jpg" rel="nofollow">http://i.stack.imgur.com/4YdpM.jpg</a>
  I added a little explanation of result that I got. We can divide texture by two parts (triangles). In first case, I get this part switched around diagonal. In second case, I get a good mapping according to divided texture, but I cannot understand why it works.
  Sorry, if my explanation not so clear. </p>