'\" t
.\"     Title: glClipControl
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 01/03/2018
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
.\"
.TH "GLCLIPCONTROL" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
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.nh
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.SH "NAME"
glClipControl \- control clip coordinate to window coordinate behavior
.SH "C SPECIFICATION"
.HP \w'void\ glClipControl('u
.BI "void glClipControl(GLenum\ " "origin" ", GLenum\ " "depth" ");"
.SH "PARAMETERS"
.PP
\fIorigin\fR
.RS 4
Specifies the clip control origin\&. Must be one of
\fBGL_LOWER_LEFT\fR
or
\fBGL_UPPER_LEFT\fR\&.
.RE
.PP
\fIdepth\fR
.RS 4
Specifies the clip control depth mode\&. Must be one of
\fBGL_NEGATIVE_ONE_TO_ONE\fR
or
\fBGL_ZERO_TO_ONE\fR\&.
.RE
.SH "DESCRIPTION"
.PP
\fBglClipControl\fR
controls the clipping volume behavior and the clip coordinate to window coordinate transformation behavior\&.
.PP
The view volume is defined by $$z_{min} \eleq z_c \eleq w_c$$ where $z_{min} = \-w_c$ when
\fIdepth\fR
is
\fBGL_NEGATIVE_ONE_TO_ONE\fR, and $z_{min} = 0$ when
\fIdepth\fR
is
\fBGL_ZERO_TO_ONE\fR\&.
.PP
The normalized device coordinate $y_d$ is given by $$y_d = { { f \etimes y_c } \eover w_c }$$ where $f = 1$ when
\fIorigin\fR
is
\fBGL_LOWER_LEFT\fR, and $f = \-1$ when
\fIorigin\fR
is
\fBGL_UPPER_LEFT\fR\&.
.PP
The window coordinate $z_w$ is given by $$z_w = s \etimes z_d + b$$ where $s = { { f \- n } \eover 2 }$ and $b = { {n + f} \eover 2 }$ when
\fIdepth\fR
is
\fBGL_NEGATIVE_ONE_TO_ONE\fR, and $s = f \- n$ and $b = n$ when
\fIdepth\fR
is
\fBGL_ZERO_TO_ONE\fR\&. $n$ and $f$ are the near and far depth range values set with
\fBglDepthRange\fR()\&.
.PP
Finally, the polygon area computation defined by
\fBgl_FrontFacing\fR()
to determine if a polygon is front\- or back\-facing has its sign negated when
\fIorigin\fR
is
\fBGL_UPPER_LEFT\fR\&.
.SH "NOTES"
.PP
The default GL clip volume definition is for a
\fIorigin\fR
of
\fBGL_LOWER_LEFT\fR
and a
\fIdepth\fR
of
\fBGL_NEGATIVE_ONE_TO_ONE\fR\&.
.PP
An
\fIorigin\fR
of
\fBGL_UPPER_LEFT\fR
and a
\fIdepth\fR
of
\fBGL_ZERO_TO_ONE\fR
corresponds to Direct3D\*(Aqs clip volume definition\&.
.PP
An
\fIorigin\fR
of
\fBGL_UPPER_LEFT\fR
and a
\fIdepth\fR
of
\fBGL_NEGATIVE_ONE_TO_ONE\fR
corresponds to the upper\-left origin of the window coordinate system of Microsoft Windows and the X Window System\&.
.PP
There is extensive discussion of the uses and further consequences of the different clip volume settings in the
GL_ARB_clip_control
extension specification in the OpenGL Registry at URL
\m[blue]\fBhttp://www\&.opengl\&.org/registry/\fR\m[]\&.
.SH "ERRORS"
.PP
An
\fBGL_INVALID_ENUM\fR
error is generated if
\fIorigin\fR
is not
\fBGL_LOWER_LEFT\fR
or
\fBGL_UPPER_LEFT\fR\&.
.PP
An
\fBGL_INVALID_ENUM\fR
error is generated if
\fIdepth\fR
is not
\fBGL_NEGATIVE_ONE_TO_ONE\fR
or
\fBGL_ZERO_TO_ONE\fR\&.
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Version\fR
T}
T{
\fBFunction / Feature Name\fR
T}:T{
\fB2\&.0\fR
T}:T{
\fB2\&.1\fR
T}:T{
\fB3\&.0\fR
T}:T{
\fB3\&.1\fR
T}:T{
\fB3\&.2\fR
T}:T{
\fB3\&.3\fR
T}:T{
\fB4\&.0\fR
T}:T{
\fB4\&.1\fR
T}:T{
\fB4\&.2\fR
T}:T{
\fB4\&.3\fR
T}:T{
\fB4\&.4\fR
T}:T{
\fB4\&.5\fR
T}
.T&
l c c c c c c c c c c c c.
T{
\fBglClipControl\fR
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
✔
T}
.TE
.sp 1
.SH "SEE ALSO"
.PP
\fBgl_ClipDistance\fR(),
\fBgl_CullDistance\fR(),
\fBgl_FrontFacing\fR(),
\fBglDepthRange\fR()\&.
.SH "COPYRIGHT"
.PP
Copyright
\(co
2014 Khronos Group\&. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1\&.0, 8 June 1999\&.
\m[blue]\fBhttp://opencontent\&.org/openpub/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 2014 Khronos Group
.br