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=
"faceforward">
9 <holder>Khronos Group
</holder>
12 <refentrytitle>faceforward
</refentrytitle>
13 <manvolnum>3G
</manvolnum>
16 <refname>faceforward
</refname>
17 <refpurpose>return a vector pointing in the same direction as another
</refpurpose>
19 <refsynopsisdiv><title>Declaration
</title>
22 <funcdef>genType
<function>faceforward
</function></funcdef>
23 <paramdef>genType
<parameter>N
</parameter></paramdef>
24 <paramdef>genType
<parameter>I
</parameter></paramdef>
25 <paramdef>genType
<parameter>Nref
</parameter></paramdef>
28 <funcdef>genDType
<function>faceforward
</function></funcdef>
29 <paramdef>genDType
<parameter>N
</parameter></paramdef>
30 <paramdef>genDType
<parameter>I
</parameter></paramdef>
31 <paramdef>genDType
<parameter>Nref
</parameter></paramdef>
35 <refsect1 id=
"parameters"><title>Parameters
</title>
38 <term><parameter>N
</parameter></term>
41 Specifies the vector to orient.
46 <term><parameter>I
</parameter></term>
49 Specifies the incident vector.
54 <term><parameter>Nref
</parameter></term>
57 Specifies the reference vector.
63 <refsect1 id=
"description"><title>Description
</title>
65 <function>faceforward
</function> orients a vector to point away from a surface as defined by its normal.
66 If
<citerefentry><refentrytitle>dot
</refentrytitle></citerefentry><code>(
<parameter>Nref
</parameter>,
<parameter>I
</parameter>)
< 0</code>
67 <function>faceforward
</function> returns
<parameter>N
</parameter>, otherwise it returns
<code>-
<parameter>N
</parameter></code>.
70 <refsect1 id=
"versions"><title>Version Support
</title>
71 <informaltable frame=
"topbot">
76 <entry>faceforward (genType)
</entry>#newin11#
79 <entry>faceforward (genDType)
</entry>#newin40#
85 <refsect1 id=
"seealso"><title>See Also
</title>
87 <citerefentry><refentrytitle>reflect
</refentrytitle></citerefentry>,
88 <citerefentry><refentrytitle>refract
</refentrytitle></citerefentry>
91 <refsect1 id=
"Copyright"><title>Copyright
</title>
93 Copyright
<trademark class=
"copyright"></trademark> 2011 Khronos Group.
94 This material may be distributed subject to the terms and conditions set forth in
95 the Open Publication License, v
1.0,
8 June
1999.
96 <ulink url=
"http://opencontent.org/openpub/">http://opencontent.org/openpub/
</ulink>.