concave(3G)

NAME
     concave - allows the system to draw concave polygons

C SPECIFICATION
     void concave(b)
     Boolean b;

PARAMETERS
     b   expects either TRUE or FALSE.

         TRUE tells the system to expect concave polygons.

         FALSE tells the system to expect no concave polygons. This is the
         default.

DESCRIPTION
     concave tells the system whether or not to expect concave polygons. If
     you try to draw a concave polygon while the system does not expect it,
     the results are unpredictable. Although calling concave(TRUE) guarantees
     that all non-selfintersecting polygons will be drawn correctly, the
     performance of non-concave polygons is reduced on some machines.
     Polygons whose edges intersect each other are never guaranteed to be
     drawn correctly.

     In all cases, performance is optimized when concave polygons are
     decomposed into convex pieces before being passed to a GL drawing
     routine.

SEE ALSO
     bgnpolygon

BUG
     IRIS-4D GT and GTX models always expect concave polygons, regardless of
     the value of the concave flag.

     On Impact and Infinite Reality concave(TRUE) severely hurts performance,
     and self-intersecting four sided polygons may not render correctly.