'\" t
.\"     Title: gl_Layer
.\"    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 "GL_LAYER" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
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.nh
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.SH "NAME"
gl_Layer \- contains the selected layer of a multi\-layer framebuffer attachment
.SH "DECLARATION"
.PP
.nf
// Geometry stage
.fi
.sp

out\ \&int\ \&gl_Layer\ \&;
.PP
.nf
// Fragment stage
.fi
.sp

in\ \&int\ \&gl_Layer\ \&;
.SH "DESCRIPTION"
.PP
In the geometry language,
\fIgl_Layer\fR
is used to select a specific layer (or face and layer of cube map) in a multi\-layer framebuffer attachment\&. The actual layer used will come from one of the vertices in the primitive being shaded\&. Which vertex the layer comes from is undefined and as such it is recommended to write the same value to
\fIgl_Layer\fR
for all vertices in the primitive\&. If a shader statically assigns a value to
\fIgl_Layer\fR, layered rendering mode is enabled\&. If a shader statically assigns a value to
\fIgl_Layer\fR, and there is an execution path through the shader that does not set
\fIgl_Layer\fR, then the value of
\fIgl_Layer\fR
is undefined for invocations of the shader that take that path\&.
.PP
When used with an array of cube map textures, the
\fIgl_Layer\fR
output variable takes on a special value\&. Instead of referring to only the layer, it is used to select a cube map face and a layer\&. Setting
\fIgl_Layer\fR
to the value
layer*6+face
will render to
face
of the cube defined in
layer\&. The face values are as follows:
.TS
allbox tab(:);
lB cB.
T{
\fB Face Value \fR
T}:T{
\fB Resulting Target \fR
T}
.T&
l c
l c
l c
l c
l c
l c.
T{
0
T}:T{
\fBGL_TEXTURE_CUBEMAP_POSITIVE_X\fR
T}
T{
1
T}:T{
\fBGL_TEXTURE_CUBEMAP_NEGATIVE_X\fR
T}
T{
2
T}:T{
\fBGL_TEXTURE_CUBEMAP_POSITIVE_Y\fR
T}
T{
3
T}:T{
\fBGL_TEXTURE_CUBEMAP_NEGATIVE_Y\fR
T}
T{
4
T}:T{
\fBGL_TEXTURE_CUBEMAP_POSITIVE_Z\fR
T}
T{
5
T}:T{
\fBGL_TEXTURE_CUBEMAP_NEGATIVE_Z\fR
T}
.TE
.sp 1
.PP
For example, to render to the positive y cube map face located in the 5th
layer of the cube map array,
\fIgl_Layer\fR
should be set to
5*6+2\&.
.PP
The input variable
\fIgl_Layer\fR
in the fragment language will have the same value that was written to the output variable
\fIgl_Layer\fR
in the geometry language\&. If the geometry stage does not dynamically assign a value to
\fIgl_Layer\fR, the value of
\fIgl_Layer\fR
in the fragment stage will be undefined\&. If the geometry stage makes no static assignment to
\fIgl_Layer\fR, the input
\fIgl_Layer\fR
in the fragment stage will be zero\&. Otherwise, the fragment stage will read the same value written by the geometry stage, even if that value is out of range\&. If a fragment shader contains a static access to
\fIgl_Layer\fR, it will count against the implementation defined limit for the maximum number of inputs to the fragment stage\&.
.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 Shading Language Version\fR
T}
T{
\fBFunction Name\fR
T}:T{
\fB1\&.10\fR
T}:T{
\fB1\&.20\fR
T}:T{
\fB1\&.30\fR
T}:T{
\fB1\&.40\fR
T}:T{
\fB1\&.50\fR
T}:T{
\fB3\&.30\fR
T}:T{
\fB4\&.00\fR
T}:T{
\fB4\&.10\fR
T}:T{
\fB4\&.20\fR
T}:T{
\fB4\&.30\fR
T}:T{
\fB4\&.40\fR
T}:T{
\fB4\&.50\fR
T}
.T&
l c c c c c c c c c c c c
l c c c c c c c c c c c c.
T{
gl_Layer (geometry stage)
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}
T{
gl_Layer (fragment stage)
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_ViewportIndex\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 2012-2014 Khronos Group
.br