define front- and back-facing polygons
Signature
Parameters
| Variables | Description |
|---|---|
| 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 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.
Errors
GL_INVALID_ENUM
is generated if
mode
is not an accepted value.
Associated Gets
glGet
with argument
GL_FRONT_FACE
See Also
Copyright
Copyright
1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/
.
Sample Code References
The following code samples have been found which appear to reference the functions described here. Take care that the code may be old, broken or not even use PyOpenGL.
glFrontFace