glFrontFace - define front- and back-facing polygons
GLenum mode );
Specifies the orientation of front-facing polygons. GL_CW
and GL_CCW are accepted. The initial 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. 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.
GL_INVALID_ENUM is generated if mode is not an accepted
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
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