glFrontFace -	define front- and back-facing polygons

	  void glFrontFace( GLenum mode	)

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

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

	  GL_INVALID_ENUM is generated if mode is not an accepted

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

	  glGet	with argument GL_FRONT_FACE

	  glCullFace, glLightModel