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<!DOCTYPE refentry [ <!ENTITY % mathent SYSTEM "math.ent"> %mathent; ]>
<!-- Converted by db4-upgrade version 1.1 -->
<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="gl_SampleID">
<info>
<copyright>
<year>2011-2014</year>
<holder>Khronos Group</holder>
</copyright>
</info>
<refmeta>
<refentrytitle>gl_SampleID</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>gl_SampleID</refname>
<refpurpose>contains the index of the sample currently being processed</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Declaration</title>
<fieldsynopsis>
<modifier>in</modifier>
<type>int</type>
<varname>gl_SampleID</varname>
</fieldsynopsis>
</refsynopsisdiv>
<refsect1 xml:id="description"><title>Description</title>
<para>
<varname>gl_SampleID</varname> is a fragment language input variable that contains
the index of the sample currently being processed. This variable is in the range
0 to <citerefentry><refentrytitle>gl_NumSamples</refentrytitle></citerefentry> - 1, where
<citerefentry><refentrytitle>gl_NumSamples</refentrytitle></citerefentry>
is the total number of samples in each fragment for the current framebuffer (and thus 1 if
rendering to a non-multisample buffer). Any static use of this variable in a fragment
shader causes the entire shader to be evaluated per-sample rather than per-fragment.
</para>
<para>
When rendering to a non-multisample buffer, or if multisample rasterization is disabled,
<varname>gl_SampleID</varname> will always be zero. <citerefentry><refentrytitle>gl_NumSamples</refentrytitle></citerefentry>
is the sample count of the framebuffer regardless of whether multisample rasterization is
enabled or not.
</para>
</refsect1>
<refsect1 xml:id="versions"><title>Version Support</title>
<informaltable>
<tgroup cols="13" align="left">
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="varhead.xml" xpointer="xpointer(/*/*)"/>
<tbody>
<row>
<entry>gl_SampleID</entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="version.xml" xpointer="xpointer(/*/*[@role='40']/*)"/>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 xml:id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>gl_SamplePosition</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>gl_NumSamples</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 xml:id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="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.
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://opencontent.org/openpub/">http://opencontent.org/openpub/</link>.
</para>
</refsect1>
</refentry>
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