glFrontFace

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.  GL_CW and
	     GL_CCW are accepted.  The initial value is GL_CCW.

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 GL_CULL_FACE.

       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
       counterclockwise 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 win-
       dow coordinates, or counterclockwise winding  in	 window	 coordinates,
       are taken to be front-facing.  Passing GL_CCW to mode selects counter-
       clockwise polygons as front-facing; GL_CW selects  clockwise  polygons
       as  front-facing.   By default, counterclockwise polygons are taken to
       be front-facing.

ERRORS
       GL_INVALID_ENUM is generated if mode is not an accepted value.

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

ASSOCIATED GETS
       glGet with argument GL_FRONT_FACE

SEE ALSO
       glCullFace(3G), glLightModel(3G)



							      GLFRONTFACE(3G)