glFrontFace -	define front- and back-facing polygons

glFrontFace
	glFrontFace(mode) -> None

void glFrontFace( GLenum mode	)

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

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
value.

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