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.\"     Title: gl_FragCoord
.\"    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
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.TH "GL_FRAGCOORD" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
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.SH "NAME"
gl_FragCoord \- contains the window\-relative coordinates of the current fragment
.SH "DECLARATION"
in\ \&vec4\ \&gl_FragCoord\ \&;.SH "DESCRIPTION"
.PP
Available only in the fragment language,
\fIgl_FragCoord\fR
is an input variable that contains the window relative coordinate (x, y, z, 1/w) values for the fragment\&. If multi\-sampling, this value can be for any location within the pixel, or one of the fragment samples\&. This value is the result of fixed functionality that interpolates primitives after vertex processing to generate fragments\&. The z component is the depth value that would be used for the fragment\*(Aqs depth if no shader contained any writes to
\fBgl_FragDepth\fR()\&.
.PP
\fIgl_FragCoord\fR
may be redeclared with the additional layout qualifier identifiers
\fBorigin_upper_left\fR
or
\fBpixel_center_integer\fR\&. By default,
\fIgl_FragCoord\fR
assumes a lower\-left origin for window coordinates and assumes pixel centers are located at half\-pixel centers\&. For example, the (x, y) location (0\&.5, 0\&.5) is returned for the lower\-left\-most pixel in a window\&. The origin of
\fIgl_FragCoord\fR
may be changed by redeclaring
\fIgl_FragCoord\fR
with the
\fBorigin_upper_left\fR
identifier\&. The values returned can also be shifted by half a pixel in both x and y by
\fBpixel_center_integer\fR
so it appears the pixels are centered at whole number pixel offsets\&. This moves the (x, y) value returned by
\fIgl_FragCoord\fR
of (0\&.5, 0\&.5) by default to (0\&.0, 0\&.0) with
\fBpixel_center_integer\fR\&.
.PP
If
\fIgl_FragCoord\fR
is redeclared in any fragment shader in a program, it must be redeclared in all fragment shaders in that program that have static use of
\fIgl_FragCoord\fR\&. Redeclaring
\fIgl_FragCoord\fR
with any accepted qualifier affects only
\fIgl_FragCoord\&.x\fR
and
\fIgl_FragCoord\&.y\fR\&. It has no affect on rasterization, transformation or any other part of the OpenGL pipline or language features\&.
.SH "VERSION SUPPORT"
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gl_FragCoord
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.TE
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.SH "SEE ALSO"
.PP
\fBgl_FragCoord\fR()
.SH "COPYRIGHT"
.PP
Copyright
\(co
2011\-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 2011-2014 Khronos Group
.br