frontb(3G)frontb(3G)NAME
backbu, frontb - enable and disable drawing to the back or front buffer
FORTRAN 77 SPECIFICATION
subroutine backbu(b)
logical b
subroutine frontb(b)
logical b
PARAMETERS
b is either .TRUE. or .FALSE..
.TRUE. enables updating in the back/front bitplane buffer.
.FALSE. disables updating in the back/front bitplane buffer.
DESCRIPTION
The GL supports four separate framebuffers: pop-up, overlay, underlay,
and normal. Three of these framebuffers, overlay, underlay, and normal,
can be configured in double buffer mode. When so configured, a
framebuffer includes two color bitplane buffers: one visible bitplane
buffer, called the front buffer, and one non-visible bitplane buffer,
called the back buffer. The commands swapbu and mswapb interchange the
front and back buffer assignments.
By default, when a framebuffer is configured in double buffer mode,
drawing is enabled in the back buffer, and disabled in the front buffer.
frontb and backbu enable and disable drawing into the front and back
buffers, allowing the default to be overriden. It is acceptable to
enable neither front nor back, either front or back, or both front and
back simultaneously. Note, for example, that z-buffer drawing continues
to update the z-buffer with depth values when neither the front buffer
nor the back buffer is enabled for drawing.
frontb and backbu state is maintained separately for each of the overlay,
underlay, and normal framebuffers. Calls to these routines affect the
framebuffer that is currently active, based on the current drawmode.
backbu is ignored when the currently active framebuffer is in single
buffer mode. frontb is also ignored when the currently active
framebuffer is in single buffer mode, unless zdraw is enabled for that
framebuffer (see zdraw).
After each call to gconfi, backbu is enabled and frontb is disabled.
SEE ALSO
drawmo, double, getbuf, gconfi, single, swapbu, zdraw, rightb, leftbu
Page 1
frontb(3G)frontb(3G)NOTE
IRIS-4D G, GT, and GTX models, the Personal Iris, Indigo Entry, Indy, XL,
XS, XS24, XZ, Elan and Extreme systems do not support double buffer
operation in the overlay and underlay framebuffers. IRIS-4D
RealityEngine model does not support double buffer operation in the
underlay framebuffer.
At most four color buffers, such as front-left, front-right, back-left,
back-right, and zdraw, can be rendered into simultaneously on the IRIS-4D
RealityEngine model.
Page 2