Provided by: opengl-4-man-doc_1.0~svn33624-1_all bug

NAME

       gl_Layer - contains the selected layer of a multi-layer framebuffer attachment

DECLARATION

       // Geometry stage

       out int gl_Layer ;

       // Fragment stage

       in int gl_Layer ;

DESCRIPTION

       In the geometry language, gl_Layer 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 gl_Layer for all
       vertices in the primitive. If a shader statically assigns a value to gl_Layer, layered
       rendering mode is enabled. If a shader statically assigns a value to gl_Layer, and there
       is an execution path through the shader that does not set gl_Layer, then the value of
       gl_Layer is undefined for invocations of the shader that take that path.

       When used with an array of cube map textures, the gl_Layer 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 gl_Layer to the value layer*6+face will render to face of the
       cube defined in layer. The face values are as follows:

       ┌────────────┬───────────────────────────────┐
       │ Face ValueResulting Target       │
       ├────────────┼───────────────────────────────┤
       │0           │ GL_TEXTURE_CUBEMAP_POSITIVE_X │
       ├────────────┼───────────────────────────────┤
       │1           │ GL_TEXTURE_CUBEMAP_NEGATIVE_X │
       ├────────────┼───────────────────────────────┤
       │2           │ GL_TEXTURE_CUBEMAP_POSITIVE_Y │
       ├────────────┼───────────────────────────────┤
       │3           │ GL_TEXTURE_CUBEMAP_NEGATIVE_Y │
       ├────────────┼───────────────────────────────┤
       │4           │ GL_TEXTURE_CUBEMAP_POSITIVE_Z │
       ├────────────┼───────────────────────────────┤
       │5           │ GL_TEXTURE_CUBEMAP_NEGATIVE_Z │
       └────────────┴───────────────────────────────┘

       For example, to render to the positive y cube map face located in the 5th layer of the
       cube map array, gl_Layer should be set to 5*6+2.

       The input variable gl_Layer in the fragment language will have the same value that was
       written to the output variable gl_Layer in the geometry language. If the geometry stage
       does not dynamically assign a value to gl_Layer, the value of gl_Layer in the fragment
       stage will be undefined. If the geometry stage makes no static assignment to gl_Layer, the
       input gl_Layer 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 gl_Layer, it will count against the
       implementation defined limit for the maximum number of inputs to the fragment stage.

VERSION SUPPORT

       ┌──────────┬───────────────────────────────────────────────────────────────────────────────────┐
       │          │        OpenGL Shading Language Version                                            │
       ├──────────┼──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┤
       │Function1.101.201.301.401.503.304.004.104.204.304.404.50 │
       │Name      │      │      │      │      │      │      │      │      │      │      │      │      │
       ├──────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │gl_Layer  │  -   │  -   │  -   │  -   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │  ✔   │
       │(geometry │      │      │      │      │      │      │      │      │      │      │      │      │
       │stage)    │      │      │      │      │      │      │      │      │      │      │      │      │
       ├──────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │gl_Layer  │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  ✔   │  ✔   │  ✔   │
       │(fragment │      │      │      │      │      │      │      │      │      │      │      │      │
       │stage)    │      │      │      │      │      │      │      │      │      │      │      │      │
       └──────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┘

SEE ALSO

       gl_ViewportIndex()

COPYRIGHT

       Copyright © 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.
       http://opencontent.org/openpub/.

COPYRIGHT

       Copyright © 2012-2014 Khronos Group

[FIXME: source]                             01/03/2018                               GL_LAYER(3G)