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<refentry id="glStencilMaskSeparate">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glStencilMaskSeparate</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glStencilMaskSeparate</refname>
        <refpurpose>control the front and/or back writing of individual bits in the stencil planes</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glStencilMaskSeparate</function></funcdef>
                <paramdef>GLenum <parameter>face</parameter></paramdef>
                <paramdef>GLuint <parameter>mask</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>face</parameter></term>
            <listitem>
                <para>
                    Specifies whether the front and/or back stencil writemask is updated.
                    Three symbolic constants are valid:
                    <constant>GL_FRONT</constant>,
                    <constant>GL_BACK</constant>, and
                    <constant>GL_FRONT_AND_BACK</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>mask</parameter></term>
            <listitem>
                <para>
                    Specifies a bit mask to enable and disable writing of individual bits
                    in the stencil planes.
                    Initially, the mask is all 1's.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glStencilMaskSeparate</function> controls the writing of individual bits in the stencil planes.
            The least significant 
            <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>
            bits of <parameter>mask</parameter>,
            where 
            <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>
            is the number of bits in the stencil buffer,
            specify a mask.
            Where a 1 appears in the mask,
            it's possible to write to the corresponding bit in the stencil buffer.
            Where a 0 appears,
            the corresponding bit is write-protected.
            Initially, all bits are enabled for writing.
        </para>
        <para>
            There can be two separate <parameter>mask</parameter> writemasks; one affects back-facing polygons, and the other
            affects front-facing polygons as well as other non-polygon primitives. 
            <citerefentry><refentrytitle>glStencilMask</refentrytitle></citerefentry> sets both front
            and back stencil writemasks to the same values, as if
            <citerefentry><refentrytitle>glStencilMaskSeparate</refentrytitle></citerefentry> were called
            with <parameter>face</parameter> set to <constant>GL_FRONT_AND_BACK</constant>.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
	<para>
            <function>glStencilMaskSeparate</function> is available only if
            the GL version is 2.0 or greater.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glStencilMaskSeparate</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_STENCIL_WRITEMASK</constant>, <constant>GL_STENCIL_BACK_WRITEMASK</constant>, 
            or <constant>GL_STENCIL_BITS</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glColorMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDepthMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glIndexMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilFuncSeparate</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilOpSeparate</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 2006 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.
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
        </para>
    </refsect1>
</refentry>
