zfunct(3G)

NAME
     zfunct - specifies the function used for z-buffer comparison by the
     current framebuffer

FORTRAN 77 SPECIFICATION
     subroutine zfunct(func)
     integer*4 func

PARAMETERS
     func   expects one of eight possible flags used when comparing z values.
            The available flags are:

            ZFNEVE, the z-buffer function never passes.

            ZFLESS, the z-buffer function passes if the incoming pixel z value
            is less than the z value stored in the z-buffer bitplanes.

            ZFEQUA, the z-buffer function passes if the incoming pixel z value
            is equal to the z value stored in the z-buffer bitplanes.

            ZFLEQU, the z-buffer function passes if the incoming pixel z value
            is less than or equal to the z value stored in the z-buffer
            bitplanes.  (This is the default value.)

            ZFGREA, the z-buffer function passes if the incoming pixel z value
            is greater than the z value stored in the z-buffer bitplanes.

            ZFNOTE, the z-buffer function passes if the incoming pixel z value
            is not equal to the z value stored in the z-buffer bitplanes.

            ZFGEQU, the z-buffer function passes if the incoming pixel z value
            is greater than or equal to the z value stored in the z-buffer
            bitplanes.

            ZFALWA, the z-buffer function always passes.

DESCRIPTION
     zfunct specifies the function used to compare each incoming pixel z value
     with the z value present in the z-buffer bitplanes.  For example, if func
     is ZFLESS and the incoming pixel z value is less than the z value in the
     z-buffer bitplanes, the comparison passes.  Refer to the zbuffe manual
     page for an explanation of z-buffer operation in the cases of z function
     pass and failure.

     A separate zfunct mode is retained by each of the framebuffers:  normal,
     popup, overlay, and underlay.  The current draw mode determines which z
     function value is used, and which is modified by zfunct.

SEE ALSO
     drawmo, zbuffe, zsourc
NOTES
     Currently z-buffer operation is supported only in the normal framebuffer.
     To insure compatibility with future releases of the GL, make calls to
     zfunct only while draw mode is NORMAL.

     On the Personal Iris, if you use zfunct with czclea you can increase the
     speed of buffer clearing.