   window overlays
  hi,just browsed the GLUT documentation and came across this term and the one of window layers. Didn't find much on this on google so could someone explain to me what that means?   
  bump   ;  Don't know how much "didn't find much" means for you...The overlay is a mechanism often used to display GUI elements on top of a 3D scene. The standard layer shows the scene, while the overlay shows the GUI. Menus and hints are typical candidates for overlays in general, tools especially in editors, and HUDs or rear-views in games.Using an overlay can have the advantage of decoupling GUI (e.g.) rendering from scene rendering. E.g. no need to switch explicitely between perspective and orthogonal projection, because this is done inclusively when switching to the other context:Quote:GLUT V3 specification, chapter 5 "Overlay Management"When overlay hardware is available, GLUT provides a set of routine for establishing, using, and removing an overlay for GLUT windows. When an overlay is established, a separate OpenGL context is also established. A window's overlay OpenGL state is kept distinct from the normal planes OpenGL state.