<div class="refentry"><a id="glGetUniformLocation"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glGetUniformLocation — return the location of a uniform variable</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table" 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> or if <em class="parameter"><code>name</code></em>

starts with the reserved prefix "gl_".</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"><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"><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"><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="glGetProgramiv"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</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"><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"><span class="citerefentry"><span class="refentrytitle">glIsProgram</span></span></a></p></div>

{$pipelinestall}{$examples}

<div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p><a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>,

<a class="citerefentry" href="glUniform"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a></p></div><div class="refsect1"><div id="Copyright"><h2>Copyright</h2><p>

Copyright © 2003-2005 3Dlabs Inc. Ltd.

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="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p></div></div></div>