overlay(3G) overlay(3G)
NAME
overlay - sets the number of user-defined bitplanes used for
overlay colors
SPECIFICATION
C overlay(planes)
long planes;
FORTRAN subroutine overla(planes)
integer*4 planes
DESCRIPTION
overlay sets the number of user-defined bitplanes used for
overlay colors. planes is the number of bitplanes that you
want to use for the overlay, 0 or 2. The overlay color
appears whenever any of its bits are non-zero. The system
has two bitplanes that can be allocated as underlay or
overlay. overlay sets them as overlay bitplanes allowing
three overlay colors. overlay and underlay cannot both be
set to 2 at the same time. Setting overlay to 2 forces the
underlay setting to zero, and vice versa. The default value
is 2.
Call gconfig after overlay to activate the overlay setting.
When the drawing mode is OVERDRAW, all drawing occurs in the
overlay bitplanes. In OVERDRAW, FLAT is the only available
shading model.
SEE ALSO
drawmode, gconfig, underlay
Programming Guide, Section 6.4, Overlay and Underlay Modes
NOTE
This routine is available only in immediate mode.
Page 1 (printed 8/20/87)