NAME fglFrontFace - define front- and back-facing polygons FORTRAN SPECIFICATION SUBROUTINE fglFrontFace( INTEGER*4 mode ) PARAMETERS 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 fglEnable and fglDisable 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. fglFrontFace 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. GL_INVALID_OPERATION is generated if fglFrontFace is executed between the execution of fglBegin and the corresponding execution of fglEnd. ASSOCIATED GETS fglGet with argument GL_FRONT_FACE SEE ALSO fglCullFace, fglLightModel