OpenGL man pages
glFrontFace - define front- and back-facing polygons
void glFrontFace( GLenum mode )
mode Specifies the orientation of front-facing polygons. GL_CW and GL_CCW
are accepted. The default value is GL_CCW.
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. Elimination of
back-facing polygons is enabled and disabled with glEnable and glDisable
using 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 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 counterclockwise polygons as front-facing; GL_CW
selects clockwise polygons as front-facing. By default, counterclockwise
polygons are taken to be front-facing.
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.
glGet with argument GL_FRONT_FACE
Fri Dec 6 11:18:03 EST 1996
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