upstream-man-pages/manglsl/refract.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="refract">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2011</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>refract</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>refract</refname>
  17         <refpurpose>calculate the refraction direction for an incident vector</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>Declaration</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>genType <function>refract</function></funcdef>
  23                 <paramdef>genType <parameter>I</parameter></paramdef>
  24                 <paramdef>genType <parameter>N</parameter></paramdef>
  25                 <paramdef>float <parameter>eta</parameter></paramdef>
  26             </funcprototype>
  27             <funcprototype>
  28                 <funcdef>genDType <function>refract</function></funcdef>
  29                 <paramdef>genDType <parameter>I</parameter></paramdef>
  30                 <paramdef>genDType <parameter>N</parameter></paramdef>
  31                 <paramdef>float <parameter>eta</parameter></paramdef>
  32             </funcprototype>
  33         </funcsynopsis>
  34     </refsynopsisdiv>
  35     <refsect1 id="parameters"><title>Parameters</title>
  36         <variablelist>
  37         <varlistentry>
  38             <term><parameter>I</parameter></term>
  39             <listitem>
  40                 <para>
  41                     Specifies the incident vector.
  42                 </para>
  43             </listitem>
  44         </varlistentry>
  45         <varlistentry>
  46             <term><parameter>N</parameter></term>
  47             <listitem>
  48                 <para>
  49                     Specifies the normal vector.
  50                 </para>
  51             </listitem>
  52         </varlistentry>
  53         <varlistentry>
  54             <term><parameter>eta</parameter></term>
  55             <listitem>
  56                 <para>
  57                     Specifies the ratio of indices of refraction.
  58                 </para>
  59             </listitem>
  60         </varlistentry>
  61         </variablelist>
  62     </refsect1>
  63     <refsect1 id="description"><title>Description</title>
  64         <para>
  65             For a given incident vector <parameter>I</parameter>, surface normal <parameter>N</parameter> and ratio of
  66             indices of refraction, <parameter>eta</parameter>, <function>refract</function> returns the refraction vector,
  67             <parameter>R</parameter>.
  68         </para>
  69         <para>
  70             <parameter>R</parameter> is calculated as:
  71         </para>
  72         <para>
  73             <programlisting><![CDATA[    k = 1.0 - eta * eta * (1.0 - dot(N, I) * dot(N, I));
  74     if (k < 0.0)
  75         R = genType(0.0);       // or genDType(0.0)
  76     else
  77         R = eta * I - (eta * dot(N, I) + sqrt(k)) * N;]]></programlisting>
  78         </para>
  79         <para>
  80             The input parameters <parameter>I</parameter> and <parameter>N</parameter> should be normalized in order to achieve the desired result.
  81         </para>
  82     </refsect1>
  83     <refsect1 id="versions"><title>Version Support</title>
  84         <informaltable frame="topbot">
  85             #VARTABLECOLS#
  86                 <thead>
  87                     #FUNCTABLEHEADER#
  88                     <row>
  89                         <entry>refract (genType)</entry>#newin11#
  90                     </row>
  91                     <row>
  92                         <entry>refract (genDType)</entry>#newin40#
  93                     </row>
  94                 </thead>
  95             </tgroup>
  96         </informaltable>
  97     </refsect1>
  98     <refsect1 id="seealso"><title>See Also</title>
  99         <para>
 100             <citerefentry><refentrytitle>dot</refentrytitle></citerefentry>,
 101             <citerefentry><refentrytitle>reflect</refentrytitle></citerefentry>
 102         </para>
 103     </refsect1>
 104     <refsect1 id="Copyright"><title>Copyright</title>
 105         <para>
 106             Copyright <trademark class="copyright"></trademark> 2011 Khronos Group.
 107             This material may be distributed subject to the terms and conditions set forth in
 108             the Open Publication License, v 1.0, 8 June 1999.
 109             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 110         </para>
 111     </refsect1>
 112 </refentry>