<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
<!-- saved from url=(0013)about:internet -->
<?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</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><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" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">GLint <b class="fsfunc">glGetUniformLocation</b>(</code></td><td>GLuint  </td><td><var class="pdparam">program</var>, </td></tr><tr><td> </td><td>const GLchar * </td><td><var class="pdparam">name</var><code>)</code>;</td></tr></table></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>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" lang="en" xml:lang="en"><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 href="glUniform.xml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a>
    to set the value of the uniform variable or to
    <a 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" lang="en" xml:lang="en"><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" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p><a 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 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 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 href="glIsProgram.xml"><span class="citerefentry"><span class="refentrytitle">glIsProgram</span></span></a></p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p><a href="glLinkProgram.xml"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>,
    <a href="glUniform.xml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a></p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 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 href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p></div></div></body></html>
