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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
<?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>glGetUniformLocation - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /></head><body><div class="refentry"><a id="glGetUniformLocation"></a><div class="titlepage"></div><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 border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><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"><a id="parameters"></a><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"><a id="description"></a><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.xml"><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.xml"><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"><a id="errors"></a><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"><a id="associatedgets"></a><h2>Associated Gets</h2><p><a class="citerefentry" href="glGetActiveUniform.xml"><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.xml"><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.xml"><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.xml"><span class="citerefentry"><span class="refentrytitle">glIsProgram</span></span></a></p></div><div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p><a class="citerefentry" href="glLinkProgram.xml"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>,
<a class="citerefentry" href="glUniform.xml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a></p></div><div class="refsect1"><a id="Copyright"></a><h2>Copyright</h2><p>
Copyright <span class="trademark"></span>© 2003-2005 3Dlabs Inc. Ltd.
Copyright <span class="trademark"></span>© 2010-2013 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="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p></div></div></body></html>
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