title: GL_UNSIGNED_BYTE
body: <p>I've got colors in GL_UNSIGNED_BYTE r,g,b but I want to use the alpha channel to put a custom value that is going to be used inside the pixel shader to color the geometry differently.
  There are two possible values 0 and 127 now my problem is that when I do this in the vertex shader :</p>
  
  <p>[vertex]</p>
  
  <pre><code>varying float factor;
  
  factor = gl_Color.w
  </code></pre>
  
  <p>it seems that the factor is always 1.0 because if I do this:</p>
  
  <p>[fragment]</p>
  
  <pre><code>varying float factor;
  
  factor = factor;
  
  gl_FragColor = vec4(factor, 0.0, 0.0, 1.0)
  </code></pre>
  
  <p>The output is always red why I would expect two different colors, one when the factor is zero  and one when the factor is 127.</p>
  
  <p>So if I assign two values 0 and 127 I should get in the vertex shader 0/0.5? is this correct?</p>
  
  <p>[Edit]
  Ok I see now two different values but I don't know why I get them, there s any operation the GPU does in the gl_Colow.w component I am not aware of?</p>
  
  <p>[Edit2]
  As Nicholas has pointed out I am using glColorPointer(4...); </p>