GLFRONTFACE() MachTen Programmer’s Manual GLFRONTFACE()

NAME
glFrontFace - define front- and back-facing polygons

C SPECIFICATION
void glFrontFace( GLenum mode )

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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 elimi-
nation of back-facing polygons, call glEnable and glDis-
able 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 ver-
tex, moves in a clockwise direction about the interior of
the polygon. The polygon’s winding is said to be counter-
clockwise 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 counter-
clockwise 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 clock-
wise polygons as front-facing. By default, counterclock-
wise 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 exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd.

ASSOCIATED GETS
glGet with argument GL_FRONT_FACE