title: How to correctly export an .obj using openframework's ofMesh?
body: <p>I'm using <a href="https://github.com/kylemcdonald/ofxFaceTracker" rel="nofollow noreferrer">ofxFaceTracker</a> and trying to export the face mesh:</p>
  
  <p><img src="https://i.stack.imgur.com/E8DP2.jpg" alt="face tracker mesh"></p>
  
  <p><a href="http://makematics.com/research/facetracker/" rel="nofollow noreferrer">image source</a></p>
  
  <p>I tried to export it like so:</p>
  
  <pre><code>void testApp::exportOBJ(ofMesh m,const string name){
      obj.open(ofToDataPath(name),ofFile::WriteOnly);
      obj &lt;&lt; "vertices:\n";
      for(int i = 0 ; i &lt; m.getNumVertices(); i++) {
          ofVec3f v = m.getVertex(i);
          obj &lt;&lt; "v " + ofToString(v.x) + " " + ofToString(v.y) + " " + ofToString(v.z) + "\n";
      }
      obj &lt;&lt; "faces:\n";
      for(int i = 0 ; i &lt; m.getNumIndices(); i += 3)
          obj &lt;&lt; "f " + ofToString(m.getIndex(i)) + " " + ofToString(m.getIndex(i+1)) + " " + ofToString(m.getIndex(i+2)) + "\n";
      obj &lt;&lt; "\n";
      obj.close();
      cout &lt;&lt; "wrote " &lt;&lt; name &lt;&lt; endl;
  }
  </code></pre>
  
  <p>But on osx I can't open the mesh (tried with meshlab/blender/wings3d).
  I've managed to open the same mesh on windows with rhino, and it looks mostly like a face,
  but some vertices are really distorted/in the wrong location, so my guess is I'm doing something wrong with the indices, but not sure what/how.</p>
  
  <p>Here's an example .obj exported:</p>
  
  <pre><code>vertices:
  v -20.6022 -5.66773 21.5579
  v -19.8261 -0.419152 20.9754
  v -18.7688 4.80224 20.5902
  v -17.4952 9.82323 18.4562
  v -15.6561 14.3357 13.5869
  v -12.5987 17.9449 8.00129
  v -8.53776 20.5398 3.32444
  v -3.94841 22.2104 -0.892325
  v 1.02873 22.4121 -4.53705
  v 6.18366 21.5766 -0.714729
  v 10.605 19.0508 3.50892
  v 14.2893 15.6505 8.12131
  v 17.009 11.5584 13.606
  v 18.5784 6.98063 18.3654
  v 19.3276 2.1372 20.5367
  v 19.64 -2.84804 20.831
  v 19.5423 -7.82872 21.2609
  v -17.327 -14.5225 0.123951
  v -14.9373 -16.7636 -1.52573
  v -11.8495 -17.9108 -2.87878
  v -8.56141 -18.0651 -4.1774
  v -5.32835 -17.4937 -5.38178
  v 2.79548 -17.8005 -5.4358
  v 5.63979 -18.6976 -4.14262
  v 8.66089 -18.956 -2.80534
  v 11.6497 -18.4135 -1.37405
  v 14.2054 -16.789 0.341925
  v -0.408693 -11.8925 -4.88226
  v -0.180875 -8.73332 -7.72351
  v 0.0312087 -5.60233 -10.714
  v 0.231803 -2.47574 -13.552
  v -2.84584 1.30904 -6.47237
  v -1.12265 1.67075 -7.31997
  v 0.671659 1.72685 -8.1004
  v 2.29284 1.47247 -7.20141
  v 3.78514 0.901742 -6.43822
  v -12.9266 -9.93115 -0.801998
  v -11.0504 -11.234 -1.02927
  v -8.72255 -11.4499 -1.16927
  v -6.69202 -10.4231 -1.045
  v -8.72807 -9.76957 -1.15914
  v -10.8849 -9.54587 -1.06901
  v 4.84169 -11.0086 -0.905979
  v 6.64327 -12.2275 -1.11565
  v 8.91755 -12.4115 -0.967128
  v 10.9016 -11.366 -0.685089
  v 8.99931 -10.6743 -0.93854
  v 6.88148 -10.6499 -0.986586
  v -6.31415 9.57306 -2.88979
  v -4.28127 7.70573 -5.03882
  v -1.92705 6.22388 -6.66532
  v 0.757197 6.1971 -8.35617
  v 3.3569 5.91561 -6.45012
  v 5.76649 7.07784 -4.82012
  v 7.81309 8.75701 -2.65881
  v 5.91403 10.1098 -3.89979
  v 3.55874 10.8651 -5.05484
  v 1.01962 11.0854 -6.49424
  v -1.54786 11.1077 -5.23493
  v -4.05109 10.6435 -4.02293
  v -1.89044 8.35439 -5.36359
  v 0.896875 8.06717 -7.44355
  v 3.61175 8.07349 -5.06538
  v 3.60898 8.43406 -4.47627
  v 0.941186 8.54596 -6.41103
  v -1.78114 8.73121 -4.70015
  faces:
  f 20 21 23
  f 21 22 23
  f 0 1 36
  f 15 16 45
  f 0 17 36
  f 16 26 45
  f 17 18 37
  f 25 26 44
  f 17 36 37
  f 26 44 45
  f 18 19 38
  f 24 25 43
  f 18 37 38
  f 25 43 44
  f 19 20 38
  f 23 24 43
  f 20 21 39
  f 22 23 42
  f 20 38 39
  f 23 42 43
  f 21 22 27
  f 21 27 39
  f 22 27 42
  f 27 28 42
  f 27 28 39
  f 28 42 47
  f 28 39 40
  f 1 36 41
  f 15 45 46
  f 1 2 41
  f 14 15 46
  f 28 29 40
  f 28 29 47
  f 2 40 41
  f 14 46 47
  f 2 29 40
  f 14 29 47
  f 2 3 29
  f 13 14 29
  f 29 30 31
  f 29 30 35
  f 3 29 31
  f 13 29 35
  f 30 32 33
  f 30 33 34
  f 30 31 32
  f 30 34 35
  f 3 4 31
  f 12 13 35
  f 4 5 48
  f 11 12 54
  f 5 6 48
  f 10 11 54
  f 6 48 59
  f 10 54 55
  f 6 7 59
  f 9 10 55
  f 7 58 59
  f 9 55 56
  f 8 57 58
  f 8 56 57
  f 7 8 58
  f 8 9 56
  f 4 31 48
  f 12 35 54
  f 31 48 49
  f 35 53 54
  f 31 49 50
  f 35 52 53
  f 31 32 50
  f 34 35 52
  f 32 33 50
  f 33 34 52
  f 33 50 51
  f 33 51 52
  f 48 49 60
  f 49 60 50
  f 50 60 61
  f 50 51 61
  f 51 52 61
  f 61 62 52
  f 52 53 62
  f 53 54 62
  f 54 55 63
  f 55 56 63
  f 56 63 64
  f 56 57 64
  f 64 65 57
  f 57 58 65
  f 58 59 65
  f 48 59 65
  </code></pre>
  
  <p>Any hints/tips on how I can correctly export this mesh as an .obj ?</p>