zwritemask(3G)

NAME
     zwritemask - specifies a write mask for the z-buffer of the current
     framebuffer

C SPECIFICATION
     void zwritemask(mask)
     unsigned long mask;

PARAMETERS
     mask   expects a mask indicating which z-buffer bitplanes are read only
            and which can be written to.  Z-buffer bitplanes that correspond
            to zeros in the mask are read only.  Z-buffer bitplanes that
            correspond to ones in the mask can be written.

DESCRIPTION
     zwritemask specifies a mask used to control which z-buffer bitplanes are
     written, and which are read only.  A separate mask is maintained by each
     of the framebuffers, normal, popup, overlay, and underlay.  The mask
     affects both writes to the z-buffer that are the result of z-buffer pixel
     operation, and writes resulting from zclear operation.

     zwritemask is ignored while drawing directly to the z-buffer, as when
     zdraw is TRUE. In this case the current writemask applies to the z-buffer
     as well as to the color bitplanes.

     zwritemask is initialized when a window is created, and when gconfig is
     called, to enable all z-buffer bitplanes.

SEE ALSO
     gconfig, wmpack, writemask, zbuffer, zdraw

NOTES
     Currently z-buffer operation is supported only in the normal framebuffer.
     To insure compatibility with future releases of the GL, make calls to
     zwritemask only while draw mode is NORMALDRAW.

BUGS
     This subroutine does not function on IRIS-4D B or G models.

     IRIS-4D GT and GTX models, RealityEngine models, and the Personal Iris,
     currently support a subset of z write mask functionality.  Specifically,
     zwritemask either enables or disables the writing of all z-buffer
     bitplanes. The mask passed to zwritemask will disable z-buffer writes if
     it is zero; otherwise all z-buffer bitplanes are written.  To assure
     upward compatibility with the IRIS-4D VGX and other future models, call
     zwritemask with mask equal to either 0 or 0xFFFFFFFF when all-or-nothing
     update is desired.

     On Impact and Infinite Reality individual z bitplanes are not maskable.