NAME

backface - turns on and off backfacing polygon removal

SPECIFICATION

C
backface(b)
Boolean b;

FORTRAN
subroutine backfa(b)
logical b

Pascal
procedure backface(b: Boolean);

DESCRIPTION

backface initiates or terminates backfacing polygon removal.  A backfacing polygon is defined to be a polygon whose vertices appear in clockwise order in screen space.  When backfacing polygon removal is turned on, only polygons whose vertices appear in counterclockwise order are displayed.  The backface utility improves the performance of programs which represent solid objects as collections of polygons.  Because the orientation of polygons is determined in screen space, backfacing polygon removal is not a rigorous technique.  When a polygon shrinks to the point where its vertices are coincident, its orientation is indeterminate and it is displayed.  Thus, backfacing polygon removal should be used in conjunction with some other hidden surface removal technique, such as z-buffering. 

SEE ALSO

zbuffer

Version 2.3  —  July 04, 1985