title: Using own descriptor and feature in Visual Structure From Motion
body: <p>Hi i'm using program Visual Structure From Motion to recover the structure  of a 3d-place. However, i 've already computed my descriptors and my features; so i want to use them in Visual Structure From Motion.I've read that the file which contains informations about descriptor should has the following pattern:</p>
  
  <p>[Header][Location Data][Descriptor Data][EOF]</p>
  
  <p>[Header] = int[5] = {name, version, npoint, 5, 128};
  name = ('S'+ ('I'&lt;&lt;8)+('F'&lt;&lt;16)+('T'&lt;&lt;24));
  version = ('V'+('4'&lt;&lt;8)+('.'&lt;&lt;16)+('0'&lt;&lt;24)); or ('V'+('5'&lt;&lt;8)+('.'&lt;&lt;16)+('0'&lt;&lt;24)) if containing color info
  npoint = number of features.</p>
  
  <p>[Location Data]  is a npoint x 5 float matrix and each row  is [x, y, color, scale, orientation]. 
  Write color by casting the float to unsigned char[4]
  scale &amp; orientation are only used for visualization, so you can simply write 0 for them</p>
  
  <ul>
  <li>Sort features in the order of decreasing importance, since VisualSFM may use only part of those features.</li>
  <li>VisualSFM sorts the features in the order of decreasing scales.</li>
  </ul>
  
  <p>[Descriptor Data] is a npoint x 128 unsigned char matrix. Note the feature descriptors are normalized to 512.</p>
  
  <p>[EOF]  int eof_marker = (0xff+('E'&lt;&lt;8)+('O'&lt;&lt;16)+('F'&lt;&lt;24));</p>
  
  <p>There's someone that write a concrete example of this file? This file should be generated automatically by my application.</p>