update upstream sources

[clinton/guile-figl.git] / upstream-doc / manglsl / gl_PointSize.xml

<?xml version="1.0" encoding="UTF-8"?>\r
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"\r
              "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">\r
<refentry id="gl_PointSize">\r
    <refmeta>\r
        <refmetainfo>\r
            <copyright>\r
                <year>2013</year>\r
                <holder>Khronos Group</holder>\r
            </copyright>\r
        </refmetainfo>\r
        <refentrytitle>gl_PointSize</refentrytitle>\r
        <manvolnum>3G</manvolnum>\r
    </refmeta>\r
    <refnamediv>\r
        <refname>gl_PointSize</refname>\r
        <refpurpose>contains size of rasterized points, in pixels</refpurpose>\r
    </refnamediv>\r
    <refsynopsisdiv><title>Declaration</title>\r
        <para>\r
            <function>gl_PointSize</function> is a member of the <function>gl_PerVertex</function>\r
            named block:\r
        </para>\r
        <funcsynopsis>\r
<programlisting><![CDATA[    out gl_PerVertex {\r
        vec4 gl_Position;\r
        float gl_PointSize;\r
        float gl_ClipDistance[];\r
    };]]></programlisting>\r
        </funcsynopsis>\r
    </refsynopsisdiv>\r
    <refsect1 id="description"><title>Description</title>\r
        <para>\r
            In the vertex, tessellation evaluation and geometry languages, a single\r
            global instance of the <function>gl_PerVertex</function> named block is available and\r
            its <function>gl_PointSize</function> member is an output that receives the\r
            intended size of the point to be rasterized, in pixels. It may be written at any time\r
            during shader execution. If <constant>GL_PROGRAM_POINT_SIZE</constant> is enabled,\r
            <function>gl_PointSize</function> is used to determine the size of rasterized\r
            points, otherwise it is ignored by the rasterization stage.\r
        </para>\r
        <para>\r
            In the tessellation control language, the <function>gl_PerVertex</function> named block\r
            is used to construct an array, <function>gl_out[]</function>, whose members become\r
            available as inputs to the subsequent tessellation evaluation shader.\r
        </para>\r
        <para>\r
            The value of <function>gl_PointSize</function> (or the <function>gl_PointSize</function> member of the <function>gl_out[]</function>\r
            array, in the case of the tessellation control shader)\r
            is undefined after the vertex, tessellation control, and tessellation evaluation\r
            shading stages if the corresponding shader executable does\r
            not write to gl_PointSize. It is also undefined after the geometry processing stage if the geometry shader executable calls\r
            <citerefentry><refentrytitle>EmitVertex</refentrytitle></citerefentry> without having\r
            written <function>gl_PointSize</function> since the last call to <citerefentry><refentrytitle>EmitVertex</refentrytitle></citerefentry>\r
            (or hasn't written it at all).\r
        </para>\r
        <para>\r
            In the tessellation control, tessellation evaluation and geometry languages,\r
            the <function>gl_PerVertex</function> named block is used to construct an array, <function>gl_in[]</function>\r
            of per-vertex or per-control point inputs whose content represents the corresponding\r
            outputs written by the previous stage.\r
         </para>\r
    </refsect1>\r
    <refsect1 id="versions"><title>Version Support</title>\r
        <informaltable frame="topbot">\r
            #VARTABLECOLS#\r
                <thead>\r
                    #VARTABLEHEADER#\r
                    <row>\r
                        <entry>gl_PointSize (vertex shader)</entry>#newin11#\r
                    </row>\r
                    <row>\r
                        <entry>gl_PointSize (geometry shader)</entry>#newin15#\r
                    </row>\r
                    <row>\r
                        <entry>gl_PointSize (tessellation evaluation shader)</entry>#newin40#\r
                    </row>\r
                </thead>\r
            </tgroup>\r
        </informaltable>\r
    </refsect1>\r
    <refsect1 id="seealso"><title>See Also</title>\r
        <para>\r
            <citerefentry><refentrytitle>gl_Position</refentrytitle></citerefentry>, <citerefentry><refentrytitle>gl_ClipDistance</refentrytitle></citerefentry>\r
        </para>\r
    </refsect1>\r
    <refsect1 id="Copyright"><title>Copyright</title>\r
        <para>\r
            Copyright <trademark class="copyright"></trademark> 2011-2013 Khronos Group. \r
            This material may be distributed subject to the terms and conditions set forth in \r
            the Open Publication License, v 1.0, 8 June 1999.\r
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r
        </para>\r
    </refsect1>\r
</refentry>\r