upstream-man-pages/manglsl/gl_PointSize.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="gl_PointSize">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2011</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>gl_PointSize</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>gl_PointSize</refname>
  17         <refpurpose>contains size of rasterized points, in pixels</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>Declaration</title>
  20         <para>
  21             <function>gl_PointSize</function> is a member of the <function>gl_PerVertex</function>
  22             named block:
  23         </para>
  24         <funcsynopsis>
  25 <programlisting><![CDATA[    out gl_PerVertex {
  26         vec4 gl_Position;
  27         float gl_PointSize;
  28         float gl_ClipDistance[];
  29     };]]></programlisting>
  30         </funcsynopsis>
  31     </refsynopsisdiv>
  32     <refsect1 id="description"><title>Description</title>
  33         <para>
  34             In the vertex, tessellation evaluation and geoemtry languages, a single
  35             global instance of the <function>gl_PerVertex</function> named block is available and
  36             its <function>gl_PointSize</function> member is an output that receives the
  37             intended size of the point to be rasterized, in pixels. It may be written at any time
  38             during shader execution. If <constant>GL_PROGRAM_POINT_SIZE</constant> is enabled,
  39             <function>gl_PointSize</function> is used to determine the size of rasterized
  40             points, otherwise it is ignored by the rasterization stage.
  41         </para>
  42         <para>
  43             In the tessellation control language, the <function>gl_PerVertex</function> named block
  44             is used to construct an array, <function>gl_out[]</function>, whose members become
  45             available as inputs to the subsequent tessellation evaluation shader.
  46         </para>
  47         <para>
  48             The value of <function>gl_PointSize</function> (or the <function>gl_PointSize</function> member of the <function>gl_out[]</function>
  49             array, in the case of the tessellation control shader)
  50             is undefined after the vertex, tessellation control, and tessellation evaluation
  51             shading stages if the corresponding shader executable does
  52             not write to gl_PointSize. It is also undefined after the geometry processing stage if the geometry shader executable calls
  53             <citerefentry><refentrytitle>EmitVertex</refentrytitle></citerefentry> without having
  54             written <function>gl_PointSize</function> since the last call to <citerefentry><refentrytitle>EmitVertex</refentrytitle></citerefentry>
  55             (or hasn't written it at all).
  56         </para>
  57         <para>
  58             In the tessellation control, tessellation evaluation and geoemetry languages,
  59             the <function>gl_PerVertex</function> named block is used to construct an array, <function>gl_in[]</function>
  60             of per-vertex or per-control point inputs whose content represents the corresponding
  61             outputs written by the previous stage.
  62          </para>
  63     </refsect1>
  64     <refsect1 id="versions"><title>Version Support</title>
  65         <informaltable frame="topbot">
  66             #VARTABLECOLS#
  67                 <thead>
  68                     #VARTABLEHEADER#
  69                     <row>
  70                         <entry>gl_PointSize (vertex shader)</entry>#newin11#
  71                     </row>
  72                     <row>
  73                         <entry>gl_PointSize (geometry shader)</entry>#newin15#
  74                     </row>
  75                 </thead>
  76             </tgroup>
  77         </informaltable>
  78     </refsect1>
  79     <refsect1 id="seealso"><title>See Also</title>
  80         <para>
  81             <citerefentry><refentrytitle>gl_Position</refentrytitle></citerefentry>, <citerefentry><refentrytitle>gl_ClipDistance</refentrytitle></citerefentry>
  82         </para>
  83     </refsect1>
  84     <refsect1 id="Copyright"><title>Copyright</title>
  85         <para>
  86             Copyright <trademark class="copyright"></trademark> 2011 Khronos Group.
  87             This material may be distributed subject to the terms and conditions set forth in
  88             the Open Publication License, v 1.0, 8 June 1999.
  89             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
  90         </para>
  91     </refsect1>
  92 </refentry>