   Backgrounds
  What do I do to a projection transformation to ensure that a single billboard quad always takes up the entire projection window?   
  This is an OpenGL or DirectX question.  Use 2D perspective:glViewport(*rect)glMatrixMode(GL_PROJECTION)glLoadIdentity()gluOrtho2D(rect[0],rect[0]+rect[2],rect[1],rect[1]+rect[3])glMatrixMode(GL_MODELVIEW)glLoadIdentity()