
<refentry id="glGetClipPlane">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glGetClipPlane</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glGetClipPlane</refname>
        <refpurpose>return the coefficients of the specified clipping plane</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glGetClipPlane</function></funcdef>
                <paramdef>GLenum <parameter>plane</parameter></paramdef>
                <paramdef>GLdouble * <parameter>equation</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>plane</parameter></term>
            <listitem>
                <para>
                    Specifies a clipping plane.
                    The number of clipping planes depends on the implementation,
                    but at least six clipping planes are supported.
                    They are identified by symbolic names of the form <constant>GL_CLIP_PLANE</constant>
                    <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
                    where i ranges from 0 to the value of <constant>GL_MAX_CLIP_PLANES</constant> - 1.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>equation</parameter></term>
            <listitem>
                <para>
                    Returns four double-precision values that are the coefficients of the plane equation of <parameter>plane</parameter> in eye coordinates.
                    The initial value is (0, 0, 0, 0).
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glGetClipPlane</function> returns in <parameter>equation</parameter> the four coefficients of the plane equation
            for <parameter>plane</parameter>.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            It is always the case that <constant>GL_CLIP_PLANE</constant>
            <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
            = <constant>GL_CLIP_PLANE0</constant> + 
            <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>.
        </para>
        <para>
            If an error is generated,
            no change is made to the contents of <parameter>equation</parameter>.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>plane</parameter> is not an accepted value.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glGetClipPlane</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="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glClipPlane</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>
