title: In OpenGL, can I draw a pixel that exactly at the coordinates (5, 5)?
body: <p>By (5, 5) I mean exactly the fifth row and fifth column.</p>
  
  <p>I found it very hard to draw things using screen coordinates, all the coordinates in OpenGL is relative, and usually ranging from -1.0 to 1.0. Why it is so serious to prevent programmers from using screen coordinates / window coordinates?</p>