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<?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>glGetUniform - OpenGL 3.3 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glGetUniform"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glGetUniform — Returns the value 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" style="padding-bottom: 1em"><tr><td><code class="funcdef">void <b class="fsfunc">glGetUniformfv</b>(</code></td><td>GLuint  </td><td><var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">location</var>, </td></tr><tr><td> </td><td>GLfloat * </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr><td><code class="funcdef">void <b class="fsfunc">glGetUniformiv</b>(</code></td><td>GLuint  </td><td><var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">location</var>, </td></tr><tr><td> </td><td>GLint * </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glGetUniformuiv</b>(</code></td><td>GLuint  </td><td><var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">location</var>, </td></tr><tr><td> </td><td>GLuint * </td><td><var class="pdparam">params</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>location</code></em></span></dt><dd><p>Specifies the location of the uniform variable
            to be queried.</p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p>Returns the value of the specified uniform
            variable.</p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p><code class="function">glGetUniform</code> returns in
    <em class="parameter"><code>params</code></em> the value(s) of the specified
    uniform variable. The type of the uniform variable specified by
    <em class="parameter"><code>location</code></em> determines the number of values
    returned. If the uniform variable is defined in the shader as a
    boolean, int, or float, a single value will be returned. If it
    is defined as a vec2, ivec2, or bvec2, two values will be
    returned. If it is defined as a vec3, ivec3, or bvec3, three
    values will be returned, and so on. To query values stored in
    uniform variables declared as arrays, call
    <code class="function">glGetUniform</code> for each element of the array.
    To query values stored in uniform variables declared as
    structures, call <code class="function">glGetUniform</code> for each
    field in the structure. The values for uniform variables
    declared as a matrix will be returned in column major
    order.</p><p>The locations assigned to uniform variables are not known
    until the program object is linked. After linking has occurred,
    the command
    <a href="glGetUniformLocation.xml"><span class="citerefentry"><span class="refentrytitle">glGetUniformLocation</span></span></a>
    can be used to obtain the location of a uniform variable. This
    location value can then be passed to
    <code class="function">glGetUniform</code> 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. The uniform
    variable 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="notes"></a><h2>Notes</h2><p>If an error is generated, no change is made to the
    contents of <em class="parameter"><code>params</code></em>.</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><p><code class="constant">GL_INVALID_OPERATION</code> is generated if
    <em class="parameter"><code>location</code></em> does not correspond to a valid
    uniform variable location for the specified program object.</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="glGetUniformLocation.xml"><span class="citerefentry"><span class="refentrytitle">glGetUniformLocation</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="glCreateProgram.xml"><span class="citerefentry"><span class="refentrytitle">glCreateProgram</span></span></a>,
    <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>
