glFrontFace(3) glFrontFace(3)
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 coun-
terclockwise 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 counterclock-
wise 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(3), glLightModel(3)
glFrontFace(3)
Mac OS X 10.6 - Generated Thu Sep 17 20:20:19 CDT 2009