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Manual Reference Pages  - GLFRONTFACE (3G)

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glFrontFace - define front- and back-facing polygons

CONTENTS

C Specification
Parameters
Description
Errors
Associated Gets
See Also

void glFrontFace( GLenum mode )

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 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

 glCullFace(3G),  glLightModel(3G)

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