title: send data to shader per-index(not per-vertex)
body: <p>I have some nodes and edges with same position attribute.
  I want to change color of edges on click event and I use a float vertex attribute for check activation in fragment shader and if it was 1 I will color that fragment to red.
  But I have a problem, imagine a triangle , when I selecting two edge of it the active property for all three vertex changed to one and in this time the third edge will make red because both vertex of it are active.</p>
  
  <p>So I want a way to set attribute per index and then I can use them for any edge Independently. is it possible? how?</p>
  
  <p><strong>EDIT</strong> :</p>
  
  <p>my input is like this:</p>
  
  <pre><code>pos : [x0,y0,z0 , x1,y1,z1 , x2,y2,z2] // should use with indexing
  index for pos : [0,2 , 1,2 , 0,1]
  active [0,1,1,0,1,0] // should not use with indexing
  </code></pre>
  
  <p>with giving those inputs I want some output like this</p>
  
  <pre><code>pos : [x0,y0,z0 , x2,y2,z2 , x1,y1,z1 , x2,y2,z2 , x0,y0,z0 , x1,y1,z1]
  active : [0,1,1,0,1,0]
  </code></pre>
  
  <p>Thanks in advance</p>