glFrontFace(3G) OpenGL Reference glFrontFace(3G)
NAME
glFrontFace - define front- and back-facing polygons
C SPECIFICATION
void glFrontFace( GLenum mode )
PARAMETERS
mode Specifies the orientation of front-facing polygons. GLCW and
GLCCW are accepted. The initial value is GLCCW.
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 GLCULLFACE.
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 GLCCW to mode selects counterclockwise
polygons as front-facing; GLCW selects clockwise polygons as front-
facing. By default, counterclockwise polygons are taken to be front-
facing.
ERRORS
GLINVALIDENUM is generated if mode is not an accepted value.
GLINVALIDOPERATION is generated if glFrontFace is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GLFRONTFACE
SEE ALSO
glCullFace, glLightModel
Page 1