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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>glGetUniformLocation - OpenGL 4 Reference Pages</title>
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<header/>
<div class="refentry" id="glGetUniformLocation">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>glGetUniformLocation — Returns the location of a uniform variable</p>
</div>
<div class="refsynopsisdiv">
<h2>C Specification</h2>
<div class="funcsynopsis">
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">GLint <strong class="fsfunc">glGetUniformLocation</strong>(</code>
</td>
<td>GLuint <var class="pdparam">program</var>, </td>
</tr>
<tr>
<td> </td>
<td>const GLchar *<var class="pdparam">name</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>program</code>
</em>
</span>
</dt>
<dd>
<p>Specifies the program object to be
queried.</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>name</code>
</em>
</span>
</dt>
<dd>
<p>Points to a null terminated string containing
the name of the uniform variable whose location is
to be queried.</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p><code class="function">glGetUniformLocation </code> returns an
integer that represents the location of a specific uniform
variable within a program object. <em class="parameter"><code>name</code></em>
must be a null terminated string that contains no white space.
<em class="parameter"><code>name</code></em> must be an active uniform variable
name in <em class="parameter"><code>program</code></em> that is not a structure,
an array of structures, or a subcomponent of a vector or a
matrix. This function returns -1 if <em class="parameter"><code>name</code></em>
does not correspond to an active uniform variable in
<em class="parameter"><code>program</code></em>, if <em class="parameter"><code>name</code></em>
starts with the reserved prefix "gl_", or if
<em class="parameter"><code>name</code></em> is associated with an atomic counter or
a named uniform block.</p>
<p>Uniform variables that are structures or arrays of
structures may be queried by calling
<code class="function">glGetUniformLocation</code> for each field within
the structure. The array element operator "[]" and the
structure field operator "." may be used in
<em class="parameter"><code>name</code></em> in order to select elements within
an array or fields within a structure. The result of using these
operators is not allowed to be another structure, an array of
structures, or a subcomponent of a vector or a matrix. Except if
the last part of <em class="parameter"><code>name</code></em> indicates a uniform
variable array, the location of the first element of an array
can be retrieved by using the name of the array, or by using the
name appended by "[0]".</p>
<p>The actual locations assigned to uniform variables are not
known until the program object is linked successfully. After
linking has occurred, the command
<code class="function">glGetUniformLocation</code> can be used to obtain
the location of a uniform variable. This location value can then
be passed to
<a class="citerefentry" href="glUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a>
to set the value of the uniform variable or to
<a class="citerefentry" href="glGetUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetUniform</span></span></a>
in order to query the current value of the uniform variable.
After a program object has been linked successfully, the index
values for uniform variables remain fixed until the next link
command occurs. Uniform variable locations and values can only
be queried after a link if the link was successful.</p>
</div>
<div class="refsect1" id="errors">
<h2>Errors</h2>
<p><code class="constant">GL_INVALID_VALUE</code> is generated if
<em class="parameter"><code>program</code></em> is not a value generated by
OpenGL.</p>
<p><code class="constant">GL_INVALID_OPERATION</code> is generated if
<em class="parameter"><code>program</code></em> is not a program object.</p>
<p><code class="constant">GL_INVALID_OPERATION</code> is generated if
<em class="parameter"><code>program</code></em> has not been successfully
linked.</p>
</div>
<div class="refsect1" id="associatedgets">
<h2>Associated Gets</h2>
<p><a class="citerefentry" href="glGetActiveUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniform</span></span></a>
with arguments <em class="parameter"><code>program</code></em> and the index of
an active uniform variable</p>
<p><a class="citerefentry" href="glGetProgram.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetProgram</span></span></a>
with arguments <em class="parameter"><code>program</code></em> and
<code class="constant">GL_ACTIVE_UNIFORMS</code> or
<code class="constant">GL_ACTIVE_UNIFORM_MAX_LENGTH</code></p>
<p><a class="citerefentry" href="glGetUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetUniform</span></span></a>
with arguments <em class="parameter"><code>program</code></em> and the name of a
uniform variable</p>
<p>
<a class="citerefentry" href="glIsProgram.xhtml">
<span class="citerefentry">
<span class="refentrytitle">glIsProgram</span>
</span>
</a>
</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 ; ">
<colgroup>
<col style="text-align: left; "/>
<col style="text-align: center; " class="firstvers"/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<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 Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function / Feature Name</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.4</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.5</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="function">glGetUniformLocation</code>
</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="seealso">
<h2>See Also</h2>
<p><a class="citerefentry" href="glLinkProgram.xhtml"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>,
<a class="citerefentry" href="glUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a></p>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 2003-2005 3Dlabs Inc. Ltd.
Copyright <span class="trademark"/>© 2010-2014 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>
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