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sync code with last improvements from OpenBSD

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purplerain 2023-08-28 05:57:34 +00:00
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'\" te
'\"! tbl|eqn | mmdoc
'\"macro stdmacro
.ds Vn Version 1.2
.ds Dt 24 September 1999
.ds Re Release 1.2.1
.ds Dp Jan 14 18:30
.ds Dm 01 depthfunc
.ds Xs 34310 5 depthfunc.gl
.TH GLDEPTHFUNC 3G
.SH NAME
.B "glDepthFunc
\- specify the value used for depth buffer comparisons
.SH C SPECIFICATION
void \f3glDepthFunc\fP(
GLenum \fIfunc\fP )
.nf
.fi
.SH PARAMETERS
.TP \w'\f2func\fP\ \ 'u
\f2func\fP
Specifies the depth comparison function.
Symbolic constants
\%\f3GL_NEVER\fP,
\%\f3GL_LESS\fP,
\%\f3GL_EQUAL\fP,
\%\f3GL_LEQUAL\fP,
\%\f3GL_GREATER\fP,
\%\f3GL_NOTEQUAL\fP,
\%\f3GL_GEQUAL\fP, and
\%\f3GL_ALWAYS\fP are accepted.
The initial value is \%\f3GL_LESS\fP.
.SH DESCRIPTION
\%\f3glDepthFunc\fP specifies the function used to compare each incoming pixel depth value
with the depth value present in the depth buffer.
The comparison is performed only if depth testing is enabled.
(See \%\f3glEnable\fP and \%\f3glDisable\fP of \%\f3GL_DEPTH_TEST\fP.)
.P
\f2func\fP specifies the conditions under which the pixel will be drawn.
The comparison functions are as follows:
.TP 16
\%\f3GL_NEVER\fP
Never passes.
.TP
\%\f3GL_LESS\fP
Passes if the incoming depth value is less than the stored depth value.
.TP
\%\f3GL_EQUAL\fP
Passes if the incoming depth value is equal to the stored depth value.
.TP
\%\f3GL_LEQUAL\fP
Passes if the incoming depth value is less than or equal to
the stored depth value.
.TP
\%\f3GL_GREATER\fP
Passes if the incoming depth value is greater than the stored depth value.
.TP
\%\f3GL_NOTEQUAL\fP
Passes if the incoming depth value is not equal to the stored depth value.
.TP
\%\f3GL_GEQUAL\fP
Passes if the incoming depth value is greater than or equal to
the stored depth value.
.TP
\%\f3GL_ALWAYS\fP
Always passes.
.P
The initial value of \f2func\fP is \%\f3GL_LESS\fP.
Initially, depth testing is disabled.
.NOTES
Even if the depth buffer exists and the depth mask is non-zero, the
depth buffer is not updated if the depth test is disabled.
.SH ERRORS
\%\f3GL_INVALID_ENUM\fP is generated if \f2func\fP is not an accepted value.
.P
\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glDepthFunc\fP
is executed between the execution of \%\f3glBegin\fP
and the corresponding execution of \%\f3glEnd\fP.
.SH ASSOCIATED GETS
\%\f3glGet\fP with argument \%\f3GL_DEPTH_FUNC\fP
.br
\%\f3glIsEnabled\fP with argument \%\f3GL_DEPTH_TEST\fP
.SH SEE ALSO
\%\f3glDepthRange(3G)\fP,
\%\f3glEnable(3G)\fP,
\%\f3glPolygonOffset(3G)\fP