title: Using RGB for A in fixed pipeline opengl
body: <p>Yes so short question: Is it possible to use any of the RGB components as alpha in Opengl ES 1.1 (fixed pipeline)?</p>
  
  <p>It seems that GL_COMBINE does not allow one to use the RGB as a source for alpha.</p>
  
  <p>Why is this limit imposed, and what are alternatives? I've tried quite a few things but I am unable to find a solution.</p>