
<refentry id="glPassThrough">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glPassThrough</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glPassThrough</refname>
        <refpurpose>place a marker in the feedback buffer</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glPassThrough</function></funcdef>
                <paramdef>GLfloat <parameter>token</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>token</parameter></term>
            <listitem>
                <para>
                    Specifies a marker value to be placed in the feedback buffer
                    following a <constant>GL_PASS_THROUGH_TOKEN</constant>.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
        </para>
        <para>
            Feedback is a GL render mode.
            The mode is selected by calling
            <citerefentry><refentrytitle>glRenderMode</refentrytitle></citerefentry> with <constant>GL_FEEDBACK</constant>.
            When the GL is in feedback mode,
            no pixels are produced by rasterization.
            Instead,
            information about primitives that would have been rasterized
            is fed back to the application using the GL.
            See the <citerefentry><refentrytitle>glFeedbackBuffer</refentrytitle></citerefentry> reference page for a description of the
            feedback buffer and the values in it.
        </para>
        <para>
            <function>glPassThrough</function> inserts a user-defined marker in the feedback buffer
            when it is executed in feedback mode.
            <parameter>token</parameter> is returned as if it were a primitive;
            it is indicated with its own unique identifying value:
            <constant>GL_PASS_THROUGH_TOKEN</constant>.
            The order of <function>glPassThrough</function> commands with respect to the specification
            of graphics primitives is maintained.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            <function>glPassThrough</function> is ignored if the GL is not in feedback mode.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glPassThrough</function> is executed between
            the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_RENDER_MODE</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glFeedbackBuffer</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glRenderMode</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>
