zfunct(3G)zfunct(3G)NAMEzfunct - 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.
DESCRIPTIONzfunct 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
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zfunct(3G)zfunct(3G)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.
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