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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<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>