GLFRONTFACE(3G)                                                GLFRONTFACE(3G)



NAME
       glFrontFace - define front- and back-facing polygons


C SPECIFICATION
       void glFrontFace( GLenum mode )


PARAMETERS
       mode  Specifies  the  orientation  of front-facing polygons.  GLCW and
             GLCW are accepted.  The initial value is GLCW.

DESCRIPTION
       In a scene composed entirely of  opaque  closed  surfaces,  back-facing
       polygons  are  never visible.  Eliminating these invisible polygons has
       the obvious benefit of speeding up the  rendering  of  the  image.   To
       enable  and  disable elimination of back-facing polygons, call glEnable
       and glDisable with argument GLCULFACE.

       The projection of a polygon to  window  coordinates  is  said  to  have
       clockwise  winding  if  an imaginary object following the path from its
       first vertex, its second vertex, and so on, to  its  last  vertex,  and
       finally  back to its first vertex, moves in a clockwise direction about
       the interior of the polygon.  The polygon's winding is said to be coun-
       terclockwise if the imaginary object following the same path moves in a
       counterclockwise  direction  about  the  interior   of   the   polygon.
       glFrontFace specifies whether polygons with clockwise winding in window
       coordinates, or counterclockwise winding  in  window  coordinates,  are
       taken to be front-facing.  Passing GLCW to mode selects counterclock-
       wise polygons as front-facing;  GLCW  selects  clockwise  polygons  as
       front-facing.   By  default,  counterclockwise polygons are taken to be
       front-facing.

ERORS
       GLINVALIDENUM is generated if mode is not an accepted value.

       GLINVALIDOPERATION is generated if glFrontFace  is  executed  between
       the execution of glBegin and the corresponding execution of glEnd.

ASOCIATED GETS
       glGet with argument GLFRONTFACE

SEE ALSO
       glCullFace, glLightodel



                                                               GLFRONTFACE(3G)