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.\"     Title: gl_CullDistance
.\"    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_CULLDISTANCE" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
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.SH "NAME"
gl_CullDistance \- provides a mechanism for controlling user culling
.SH "DECLARATION"
.PP
\fIgl_CullDistance\fR
is a member of the
\fIgl_PerVertex\fR
named block:
.sp
.nf
    out gl_PerVertex {
        vec4 gl_Position;
        float gl_PointSize;
        float gl_ClipDistance[];
        float gl_CullDistance[];
    };
.fi
.PP
In fragment shaders, it is intrinsically declared as:
in\ \&float\ \&gl_CullDistance[]\ \&;
.SH "DESCRIPTION"
.PP
The
\fIgl_CullDistance\fR
variable provides a mechanism for controlling user culling\&. The element
\fIgl_CullDistance\fR[\fIi\fR] specifies a cull distance for each plane
\fIi\fR\&. 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
\fIi\fR
will be discarded\&.
.PP
The
\fIgl_CullDistance\fR
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
\fIgl_MaxCullDistances\fR\&. The number of varying components consumed by
\fIgl_CullDistance\fR
will match the size of the array\&. Shaders writing
\fIgl_CullDistance\fR
must write all enabled distances, or culling results are undefined\&.
.PP
As an output variable,
\fIgl_CullDistance\fR
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
\fIgl_CullDistance\fR
array contains linearly interpolated values for the vertex values written by a shader to the
\fIgl_CullDistance\fR
vertex output variable\&.
.PP
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
\fIgl_ClipDistance\fR
and
\fIgl_CullDistance\fR
arrays to be larger than
\fIgl_MaxCombinedClipAndCullDistances\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 Shading Language Version\fR
T}
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\fBVariable Name\fR
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\fB1\&.10\fR
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\fB4\&.10\fR
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\fB4\&.20\fR
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\fB4\&.30\fR
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\fB4\&.40\fR
T}:T{
\fB4\&.50\fR
T}
.T&
l c c c c c c c c c c c c.
T{
gl_CullDistance
T}:T{
\-
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\-
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\-
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\-
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\-
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\-
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\-
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\-
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\-
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\-
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\-
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✔
T}
.TE
.sp 1
.SH "SEE ALSO"
.PP
\fBgl_ClipDistance\fR(),
\fBgl_PointSize\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