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_C_ License Applicability. Except to the extent portions of this file are
_C_ made subject to an alternative license as permitted in the SGI Free
_C_ Software License B, Version 1.1 (the "License"), the contents of this
_C_ file are subject only to the provisions of the License. You may not use
_C_ this file except in compliance with the License. You may obtain a copy
_C_ of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
_C_ Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
_C_
_C_ http://oss.sgi.com/projects/FreeB
_C_
_C_ Note that, as provided in the License, the Software is distributed on an
_C_ "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
_C_ DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
_C_ CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
_C_ PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
_C_
_C_ Original Code. The Original Code is: OpenGL Sample Implementation,
_C_ Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
_C_ Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
_C_ Copyright in any portions created by third parties is as indicated
_C_ elsewhere herein. All Rights Reserved.
_C_
_C_ Additional Notice Provisions: The application programming interfaces
_C_ established by SGI in conjunction with the Original Code are The
_C_ OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
_C_ April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
_C_ 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
_C_ Window System(R) (Version 1.3), released October 19, 1998. This software
_C_ was created using the OpenGL(R) version 1.2.1 Sample Implementation
_C_ published by SGI, but has not been independently verified as being
_C_ compliant with the OpenGL(R) version 1.2.1 Specification.
_C_
_C_ The first character in this file must be an '_'!
_C_ Anything on a line after _C_ is ignored
_define(_filters,eqn)_C_
_C_ eqn is automatically replaced with neqn for nroff
_header(FrontFace,define front- and back-facing polygons)
_names(FrontFace)
.EQ
delim $$
.EN
.SH PARAMETERS
_phead(_param1)
Specifies the orientation of front-facing polygons.
_const(CW) and _const(CCW) are accepted.
The initial value is _const(CCW).
.SH 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 _cmnd(Enable)
and _cmnd(Disable) with argument _const(CULL_FACE).
.P
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.
_cmnd specifies whether polygons with clockwise winding in window coordinates,
or counterclockwise winding in window coordinates,
are taken to be front-facing.
Passing _const(CCW) to _param1 selects counterclockwise polygons as
front-facing;
_const(CW) selects clockwise polygons as front-facing.
By default, counterclockwise polygons are taken to be front-facing.
.SH ERRORS
_const(INVALID_ENUM) is generated if _param1 is not an accepted value.
.P
_const(INVALID_OPERATION) is generated if _cmnd
is executed between the execution of _cmnd(Begin)
and the corresponding execution of _cmnd(End).
.SH ASSOCIATED GETS
_cmnd(Get) with argument _const(FRONT_FACE)
.SH SEE ALSO
_cmnd(CullFace),
_cmnd(LightModel)
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