concave(3G)							   concave(3G)

NAME    [Toc]    [Back]

     concave - allows the system to draw concave polygons

C SPECIFICATION    [Toc]    [Back]

     void concave(b)
     Boolean b;

PARAMETERS    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     bgnpolygon

BUG    [Toc]    [Back]

     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.


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