GLFRONTFACE(3G) UNIX Programmer's Manual 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.
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 elimina-
tion 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 counter-
clockwise direction about the interior of the polygon.
glFrontFace specifies whether polygons with clockwise wind-
ing 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.
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 exe-
cution of glEnd.
ASSOCIATED GETS
glGet with argument GL_FRONT_FACE
SEE ALSO
glCullFace(3G), glLightModel(3G)
MirBSD #10-current Printed 2021-12-07 1