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<refentry id="glActiveTexture">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glActiveTexture</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glActiveTexture</refname>
        <refpurpose>select active texture unit</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glActiveTexture</function></funcdef>
                <paramdef>GLenum <parameter>texture</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>texture</parameter></term>
            <listitem>
                <para>
                    Specifies which texture unit to make active. The number
                    of texture units is implementation dependent, but must be at least
                    two. <parameter>texture</parameter> must be one of 
                    <constant>GL_TEXTURE</constant><inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>,
                    where
                    i ranges from 0 to the larger of (<constant>GL_MAX_TEXTURE_COORDS</constant> - 1)
                    and (<constant>GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS</constant> - 1). 
                    The initial value is <constant>GL_TEXTURE0</constant>.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glActiveTexture</function> selects which texture unit subsequent texture state calls will
            affect.  The number of texture units an implementation supports is
            implementation dependent, but must be at least 2.
        </para>
        <para>
            Vertex arrays are client-side GL resources, which are selected by the
            <citerefentry><refentrytitle>glClientActiveTexture</refentrytitle></citerefentry> routine.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            <function>glActiveTexture</function> is only supported if the GL version is 1.3 or greater, or if
            <code>ARB_multitexture</code> is included in the string returned by
            <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry> when called with the argument <constant>GL_EXTENSIONS</constant>.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>texture</parameter> is not one of
            <constant>GL_TEXTURE</constant><inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>,
            where i ranges from 0 to the larger of (<constant>GL_MAX_TEXTURE_COORDS</constant> - 1)
            and (<constant>GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS</constant> - 1).
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_ACTIVE_TEXTURE</constant>, <constant>GL_MAX_TEXTURE_COORDS</constant>, or <constant>GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glClientActiveTexture</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glMultiTexCoord</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
        </para>
    </refsect1>
</refentry>
