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4 | <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>noise - OpenGL Shading Language (GLSL)</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="noise"></a><div class="titlepage"></div><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"><p><code class="funcdef">float <b class="fsfunc">noise1</b>(</code>genType <var class="pdparam">x</var><code>)</code>;</p><p><code class="funcdef">vec2 <b class="fsfunc">noise2</b>(</code>genType <var class="pdparam">x</var><code>)</code>;</p><p><code class="funcdef">vec3 <b class="fsfunc">noise3</b>(</code>genType <var class="pdparam">x</var><code>)</code>;</p><p><code class="funcdef">vec4 <b class="fsfunc">noise4</b>(</code>genType <var class="pdparam">x</var><code>)</code>;</p></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>x</code></em></span></dt><dd><p> | |
5 | Specifies the value to be used to seed the noise function. | |
6 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
7 | <code class="function">noise1</code>, <code class="function">noise2</code>, <code class="function">noise3</code> and <code class="function">noise4</code> return | |
8 | noise values (vector or scalar) based on the input value <em class="parameter"><code>x</code></em>. The noise function is a stochastic function | |
9 | that can be used to increase visual complexity. Values returned by the noise functions give the appearance of randomness, | |
10 | but are not truly random. They are defined to have the following characteristics: | |
11 | </p><p> | |
12 | </p><div class="itemizedlist"><ul type="disc"><li>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.</li><li>The return value(s) have an overall average of 0.0.</li><li>They are repeatable, in that a particular input value will always produce the same return value.</li><li>They are statistically invariant under rotation (i.e., no matter how the domain is rotated, it has the same statistical character).</li><li>They have a statistical invariance under translation (i.e., no matter how the domain is translated, it has the same statistical character).</li><li>They typically give different results under translation.</li><li>The spatial frequency is narrowly concentrated, centered somewhere between 0.5 to 1.0.</li><li>They are C1 continuous everywhere (i.e., the first derivative is continuous).</li></ul></div><p> | |
13 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="versions"></a><h2>Version Support</h2><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>Function</strong></span></th><th align="left"><span class="bold"><strong>Version 1.10</strong></span></th><th align="left"><span class="bold"><strong>Version 1.20</strong></span></th><th align="left"><span class="bold"><strong>Version 1.30</strong></span></th><th align="left"><span class="bold"><strong>Version 1.40</strong></span></th><th align="left"><span class="bold"><strong>Version 1.50</strong></span></th><th align="left"><span class="bold"><strong>Version 3.30</strong></span></th><th align="left"><span class="bold"><strong>Version 4.00</strong></span></th><th align="left"><span class="bold"><strong>Version 4.10</strong></span></th><th align="left"><span class="bold"><strong>Version 4.20</strong></span></th><th align="center"><span class="bold"><strong>Version 4.30</strong></span></th></tr><tr><th align="left">noise1</th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th></tr><tr><th align="left">noise2</th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th></tr><tr><th align="left">noise3</th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th></tr><tr><th align="left">noise4</th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th></tr></thead></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
14 | Copyright <span class="trademark"></span>© 2011 Khronos Group. | |
15 | This material may be distributed subject to the terms and conditions set forth in | |
16 | the Open Publication License, v 1.0, 8 June 1999. | |
17 | <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. | |
18 | </p></div></div></body></html> |