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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>noise - OpenGL 4 Reference Pages</title>
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<header/>
<div class="refentry" id="noise">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>noise — generate values with a pseudo-random noise function</p>
</div>
<div class="refsynopsisdiv">
<h2>Declaration</h2>
<div class="funcsynopsis">
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">float <strong class="fsfunc">noise1</strong>(</code>
</td>
<td>genType <var class="pdparam">x</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">vec2 <strong class="fsfunc">noise2</strong>(</code>
</td>
<td>genType <var class="pdparam">x</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">vec3 <strong class="fsfunc">noise3</strong>(</code>
</td>
<td>genType <var class="pdparam">x</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">vec4 <strong class="fsfunc">noise4</strong>(</code>
</td>
<td>genType <var class="pdparam">x</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
</div>
</div>
<div class="refsect1" id="parameters">
<h2>Parameters</h2>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<em class="parameter">
<code>x</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the value to be used to seed the noise function.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
<code class="function">noise1</code>, <code class="function">noise2</code>, <code class="function">noise3</code> and <code class="function">noise4</code> return
noise values (vector or scalar) based on the input value <em class="parameter"><code>x</code></em>. 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:
</p>
<p>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>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.</p>
</li>
<li class="listitem">
<p>The return value(s) have an overall average of 0.0.</p>
</li>
<li class="listitem">
<p>They are repeatable, in that a particular input value will always produce the same return value.</p>
</li>
<li class="listitem">
<p>They are statistically invariant under rotation (i.e., no matter how the domain is rotated, it has the same statistical character).</p>
</li>
<li class="listitem">
<p>They have a statistical invariance under translation (i.e., no matter how the domain is translated, it has the same statistical character).</p>
</li>
<li class="listitem">
<p>They typically give different results under translation.</p>
</li>
<li class="listitem">
<p>The spatial frequency is narrowly concentrated, centered somewhere between 0.5 to 1.0.</p>
</li>
<li class="listitem">
<p>They are C1 continuous everywhere (i.e., the first derivative is continuous).</p>
</li>
</ul>
</div>
<p>
</p>
</div>
<div class="refsect1" id="versions">
<h2>Version Support</h2>
<div class="informaltable">
<table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
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<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; " class="lastvers"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; ">
</th>
<th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
<span class="bold"><strong>OpenGL Shading Language Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function Name</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.10</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.20</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.30</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.40</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.50</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.30</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.00</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.10</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.20</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.30</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.40</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.50</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">noise1</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-bottom: 2px solid ; ">✔</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">noise2</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-bottom: 2px solid ; ">✔</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">noise3</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">✔</td>
<td style="text-align: center; border-bottom: 2px solid ; ">✔</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">noise4</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; ">✔</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 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.
<a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p>
</div>
</div>
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