<HTML>
<BODY>
<PRE>
<STRONG>NAME</STRONG>
<STRONG>glFrontFace</STRONG> - define front- and back-facing polygons
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>glFrontFace</STRONG>( GLenum <EM>mode</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>mode</EM> Specifies the orientation of front-facing polygons.
<STRONG>GL_CW</STRONG> and <STRONG>GL_CCW</STRONG> are accepted. The initial value is
<STRONG>GL_CCW</STRONG>.
<STRONG>DESCRIPTION</STRONG>
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 <STRONG>glEnable</STRONG> and
<STRONG>glDisable</STRONG> with argument <STRONG>GL_CULL_FACE</STRONG>.
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. <STRONG>glFrontFace</STRONG> specifies whether polygons with
clockwise winding in window coordinates, or counterclockwise
winding in window coordinates, are taken to be front-facing.
Passing <STRONG>GL_CCW</STRONG> to <EM>mode</EM> selects counterclockwise polygons as
front-facing; <STRONG>GL_CW</STRONG> selects clockwise polygons as front-
facing. By default, counterclockwise polygons are taken to
be front-facing.
<STRONG>ERRORS</STRONG>
<STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>mode</EM> is not an accepted
value.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>glFrontFace</STRONG> is executed
between the execution of <STRONG>glBegin</STRONG> and the corresponding
execution of <STRONG>glEnd</STRONG>.
<STRONG>ASSOCIATED</STRONG> <STRONG>GETS</STRONG>
<STRONG>glGet</STRONG> with argument <STRONG>GL_FRONT_FACE</STRONG>
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>glCullFace</STRONG>, <STRONG>glLightModel</STRONG>
</PRE>
</BODY>
</HTML>
