   visible entity picking/selection
  Hi All, I need some help in OpenGL, i need to select only the visible entities in a screen..any one please suggest some ideas/techniques to implement. For example if i draw a cube in a screen user can see some of the faces are visible some of them are not, i need to identify only the visible faces..Thanks   
  Here you gohttp://www.opengl.org/wiki/Common_Mistakes#Selection_and_Picking_and_Feedback_Mode