upstream-man-pages/manglsl/smoothstep.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="smoothstep">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2011</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>smoothstep</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>smoothstep</refname>
  17         <refpurpose>perform Hermite interpolation between two values</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>Declaration</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>genType <function>smoothstep</function></funcdef>
  23                 <paramdef>genType <parameter>edge0</parameter></paramdef>
  24                 <paramdef>genType <parameter>edge1</parameter></paramdef>
  25                 <paramdef>genType <parameter>x</parameter></paramdef>
  26             </funcprototype>
  27         </funcsynopsis>
  28         <funcsynopsis>
  29             <funcprototype>
  30                 <funcdef>genType <function>smoothstep</function></funcdef>
  31                 <paramdef>float <parameter>edge0</parameter></paramdef>
  32                 <paramdef>float <parameter>edge1</parameter></paramdef>
  33                 <paramdef>genType <parameter>x</parameter></paramdef>
  34             </funcprototype>
  35         </funcsynopsis>
  36         <funcsynopsis>
  37             <funcprototype>
  38                 <funcdef>genDType <function>smoothstep</function></funcdef>
  39                 <paramdef>genDType <parameter>edge0</parameter></paramdef>
  40                 <paramdef>genDType <parameter>edge1</parameter></paramdef>
  41                 <paramdef>genDType <parameter>x</parameter></paramdef>
  42             </funcprototype>
  43         </funcsynopsis>
  44         <funcsynopsis>
  45             <funcprototype>
  46                 <funcdef>genDType <function>smoothstep</function></funcdef>
  47                 <paramdef>double <parameter>edge0</parameter></paramdef>
  48                 <paramdef>double <parameter>edge1</parameter></paramdef>
  49                 <paramdef>genDType <parameter>x</parameter></paramdef>
  50             </funcprototype>
  51         </funcsynopsis>
  52     </refsynopsisdiv>
  53     <refsect1 id="parameters"><title>Parameters</title>
  54         <variablelist>
  55         <varlistentry>
  56             <term><parameter>edge0</parameter></term>
  57             <listitem>
  58                 <para>
  59                     Specifies the value of the lower edge of the Hermite function.
  60                 </para>
  61             </listitem>
  62         </varlistentry>
  63         <varlistentry>
  64             <term><parameter>edge1</parameter></term>
  65             <listitem>
  66                 <para>
  67                     Specifies the value of the upper edge of the Hermite function.
  68                 </para>
  69             </listitem>
  70         </varlistentry>
  71         <varlistentry>
  72             <term><parameter>x</parameter></term>
  73             <listitem>
  74                 <para>
  75                     Specifies the source value for interpolation.
  76                 </para>
  77             </listitem>
  78         </varlistentry>
  79         </variablelist>
  80     </refsect1>
  81     <refsect1 id="description"><title>Description</title>
  82         <para>
  83             <function>smoothstep</function> performs smooth Hermite interpolation between 0 and
  84             1 when <parameter>edge0</parameter> &lt; <parameter>x</parameter> &lt; <parameter>edge1</parameter>.
  85             This is useful in cases where a threshold function with a smooth transition is desired.
  86             <function>smoothstep</function> is equivalent to:
  87         </para>
  88         <para>
  89 <programlisting><![CDATA[    genType t;  /* Or genDType t; */
  90     t = clamp((x - edge0) / (edge1 - edge0), 0.0, 1.0);
  91     return t * t * (3.0 - 2.0 * t);
  92 ]]></programlisting>
  93         </para>
  94         <para>
  95             Results are undefined if <parameter>edge0</parameter> &ge; <parameter>edge1</parameter>.
  96         </para>
  97     </refsect1>
  98     <refsect1 id="versions"><title>Version Support</title>
  99         <informaltable frame="topbot">
 100             #VARTABLECOLS#
 101                 <thead>
 102                     #FUNCTABLEHEADER#
 103                     <row>
 104                         <entry>smoothstep (genType)</entry>#newin13#
 105                     </row>
 106                     <row>
 107                         <entry>smoothstep (genDType)</entry>#newin40#
 108                     </row>
 109                 </thead>
 110             </tgroup>
 111         </informaltable>
 112     </refsect1>
 113     <refsect1 id="seealso"><title>See Also</title>
 114         <para>
 115             <citerefentry><refentrytitle>mix</refentrytitle></citerefentry>,
 116             <citerefentry><refentrytitle>step</refentrytitle></citerefentry>
 117         </para>
 118     </refsect1>
 119     <refsect1 id="Copyright"><title>Copyright</title>
 120         <para>
 121             Copyright <trademark class="copyright"></trademark> 2011 Khronos Group.
 122             This material may be distributed subject to the terms and conditions set forth in
 123             the Open Publication License, v 1.0, 8 June 1999.
 124             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 125         </para>
 126     </refsect1>
 127 </refentry>