upstream-doc/manglsl/fwidth.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="fwidth">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2011</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>fwidth</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>fwidth</refname>
  17         <refpurpose>return the sum of the absolute derivatives in x and y</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>Declaration</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>genType <function>fwidth</function></funcdef>
  23                 <paramdef>genType <parameter>p</parameter></paramdef>
  24             </funcprototype>
  25         </funcsynopsis>
  26     </refsynopsisdiv>
  27     <refsect1 id="parameters"><title>Parameters</title>
  28         <variablelist>
  29         <varlistentry>
  30             <term><parameter>p</parameter></term>
  31             <listitem>
  32                 <para>
  33                     Specifies the expression of which to take the partial derivative.
  34                 </para>
  35             </listitem>
  36         </varlistentry>
  37         </variablelist>
  38     </refsect1>
  39     <refsect1 id="description"><title>Description</title>
  40         <para>
  41             <emphasis>Available only in the fragment shader</emphasis>, <function>fwidth</function> returns the sum of
  42             the absolute derivatives in x and y using local differencing for the input argument <parameter>p</parameter>.
  43             It is equivalent to <code><citerefentry><refentrytitle>abs</refentrytitle></citerefentry>(<citerefentry><refentrytitle>dFdx</refentrytitle></citerefentry>(p)) + <citerefentry><refentrytitle>abs</refentrytitle></citerefentry>(<citerefentry><refentrytitle>dFdy</refentrytitle></citerefentry>(p))</code>.
  44         </para>
  45     </refsect1>
  46     <refsect1 id="versions"><title>Version Support</title>
  47         <informaltable frame="topbot">
  48             #VARTABLECOLS#
  49                 <thead>
  50                     #FUNCTABLEHEADER#
  51                     <row>
  52                         <entry>fwidth</entry>#newin11#
  53                     </row>
  54                 </thead>
  55             </tgroup>
  56         </informaltable>
  57     </refsect1>
  58     <refsect1 id="seealso"><title>See Also</title>
  59         <para>
  60             <citerefentry><refentrytitle>dFdx</refentrytitle></citerefentry>,
  61             <citerefentry><refentrytitle>dFdy</refentrytitle></citerefentry>
  62         </para>
  63     </refsect1>
  64     <refsect1 id="Copyright"><title>Copyright</title>
  65         <para>
  66             Copyright <trademark class="copyright"></trademark> 2011 Khronos Group.
  67             This material may be distributed subject to the terms and conditions set forth in
  68             the Open Publication License, v 1.0, 8 June 1999.
  69             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
  70         </para>
  71     </refsect1>
  72 </refentry>