title: 3rd texture coordinate in Wavefront *.OBJ file
body: <p>What is the meaning of 3rd component in texture coords in Wavefront *.OBJ file ?</p>
  
  <p>File looks like</p>
  
  <pre><code>vt 0.8490 0.1109 -0.2498
  vt 0.8580 0.1235 -0.2498
  vt 0.8695 0.1338 -0.2498
  vt 0.8828 0.1416 -0.2498
  vt 0.9135 0.1474 -0.2360
  vt 0.8981 0.1457 -0.2360
  vt 0.8835 0.1409 -0.2360 
  </code></pre>
  
  <hr>
  
  <p>UPDATE
  Model was created in 3DS Max and source texture was PNG file. So texture is 2D</p>
  
  <hr>
  
  <p>UPDATE 2</p>
  
  <p>When I flip second coordinate then texture looks properly when I render it with OpenGL.
  3rd coordinate </p>
  
  <p>u1 = u
  v1 = 1 - v</p>
  
  <p>w - is not used at all.</p>