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NAME
       gl_CullDistance - provides a mechanism for controlling user culling


DECLARATION
       gl_CullDistance is a member of the gl_PerVertex named block:

           out gl_PerVertex {
               vec4 gl_Position;
               float gl_PointSize;
               float gl_ClipDistance[];
               float gl_CullDistance[];
           };

       In fragment shaders, it is intrinsically declared as: in float gl_CullDistance[] ;


DESCRIPTION
       The gl_CullDistance variable provides a mechanism for controlling user culling. The
       element gl_CullDistance[i] specifies a cull distance for each plane i. A distance of 0.0
       means that the vertex is on the plane, a positive distance means that the vertex is
       insider the cull volume, and a negative distance means that the point is outside the cull
       volume. Primitives whose vertices all have a negative clip distance for plane i will be
       discarded.

       The gl_CullDistance array is predeclared as unsized and must be sized by the shader either
       by redeclaring it with an size or by indexing it only with integral constant expressions.
       The size determines the number and set of enabled cull distances and can be at most
       gl_MaxCullDistances. The number of varying components consumed by gl_CullDistance will
       match the size of the array. Shaders writing gl_CullDistance must write all enabled
       distances, or culling results are undefined.

       As an output variable, gl_CullDistance provides the place for the shader to write these
       distances. As an input in all but the fragment language, it reads the values written in
       the previous shader stage. In the fragment language, the gl_CullDistance array contains
       linearly interpolated values for the vertex values written by a shader to the
       gl_CullDistance vertex output variable.

       It is a compile-time or link-time error for the set of shaders forming a program to have
       the sum of the sizes of the gl_ClipDistance and gl_CullDistance arrays to be larger than
       gl_MaxCombinedClipAndCullDistances.


VERSION SUPPORT
       ┌────────────────┬───────────────────────────────────────────────────────────────────────────────────┐
       │                │        OpenGL Shading Language Version                                            │
       ├────────────────┼──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┬──────┤
       │Variable        │ 1.10 │ 1.20 │ 1.30 │ 1.40 │ 1.50 │ 3.30 │ 4.00 │ 4.10 │ 4.20 │ 4.30 │ 4.40 │ 4.50 │
       │Name            │      │      │      │      │      │      │      │      │      │      │      │      │
       ├────────────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┤
       │gl_CullDistance │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  -   │  ✔   │
       └────────────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┘


SEE ALSO
       gl_ClipDistance(), gl_PointSize()


COPYRIGHT
       Copyright © 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 © 2014 Khronos Group

[FIXME: source]                             07/22/2015                        GL_CULLDISTANCE(3G)