'\" t
.\"     Title: noise
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: 05/21/2015
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
.\"
.TH "NOISE" "3G" "05/21/2015" "[FIXME: source]" "[FIXME: manual]"
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.SH "NAME"
noise \- generate values with a pseudo\-random noise function
.SH "DECLARATION"
.HP \w'float\ noise1('u
.BI "float noise1(genType\ " "x" ");"
.HP \w'vec2\ noise2('u
.BI "vec2 noise2(genType\ " "x" ");"
.HP \w'vec3\ noise3('u
.BI "vec3 noise3(genType\ " "x" ");"
.HP \w'vec4\ noise4('u
.BI "vec4 noise4(genType\ " "x" ");"
.SH "PARAMETERS"
.PP
\fIx\fR
.RS 4
Specifies the value to be used to seed the noise function\&.
.RE
.SH "DESCRIPTION"
.PP
\fBnoise1\fR,
\fBnoise2\fR,
\fBnoise3\fR
and
\fBnoise4\fR
return noise values (vector or scalar) based on the input value
\fIx\fR\&. The noise function is a stochastic function that can be used to increase visual complexity\&. Values returned by the noise functions give the appearance of randomness, but are not truly random\&. They are defined to have the following characteristics:
.PP
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The return value(s) are always in the range [\-1\&.0,1\&.0], and cover at least the range [\-0\&.6, 0\&.6], with a Gaussian\-like distribution\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The return value(s) have an overall average of 0\&.0\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
They are repeatable, in that a particular input value will always produce the same return value\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
They are statistically invariant under rotation (i\&.e\&., no matter how the domain is rotated, it has the same statistical character)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
They have a statistical invariance under translation (i\&.e\&., no matter how the domain is translated, it has the same statistical character)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
They typically give different results under translation\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The spatial frequency is narrowly concentrated, centered somewhere between 0\&.5 to 1\&.0\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
They are C1 continuous everywhere (i\&.e\&., the first derivative is continuous)\&.
.RE
.sp
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Shading Language Version\fR
T}
T{
\fBFunction Name\fR
T}:T{
\fB1\&.10\fR
T}:T{
\fB1\&.20\fR
T}:T{
\fB1\&.30\fR
T}:T{
\fB1\&.40\fR
T}:T{
\fB1\&.50\fR
T}:T{
\fB3\&.30\fR
T}:T{
\fB4\&.00\fR
T}:T{
\fB4\&.10\fR
T}:T{
\fB4\&.20\fR
T}:T{
\fB4\&.30\fR
T}:T{
\fB4\&.40\fR
T}:T{
\fB4\&.50\fR
T}
.T&
l c c c c c c c c c c c c
l c c c c c c c c c c c c
l c c c c c c c c c c c c
l c c c c c c c c c c c c.
T{
noise1
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}
T{
noise2
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
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T}:T{
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T}:T{
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T}:T{
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✔
T}:T{
✔
T}
T{
noise3
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
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T}:T{
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T}:T{
✔
T}:T{
✔
T}
T{
noise4
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
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T}:T{
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T}:T{
✔
T}:T{
✔
T}
.TE
.sp
.SH "COPYRIGHT"
.PP
Copyright
\(co
2011\-2014 Khronos Group\&. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1\&.0, 8 June 1999\&.
\m[blue]\fBhttp://opencontent\&.org/openpub/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 2011-2014 Khronos Group
.br