concav(3G)concav(3G)NAMEconcav - allows the system to draw concave polygons
FORTRAN 77 SPECIFICATION
subroutine concav(b)
logical 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.
DESCRIPTIONconcav 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 concav(.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
bgnpol
BUG
IRIS-4D GT and GTX models always expect concave polygons, regardless of
the value of the concav flag.
On Impact and Infinite Reality concav(.TRUE.) severely hurts
performance, and self-intersecting four sided polygons may not render
correctly.
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