upstream-man-pages/manglsl/xhtml/noise.xml

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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>