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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" /><title>glGetUniform</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /></head><body><div class="refentry"><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" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glGetUniformfv</strong>(</code></td><td>GLuint <var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">location</var>, </td></tr><tr><td> </td><td>GLfloat *<var class="pdparam">params</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glGetUniformiv</strong>(</code></td><td>GLuint <var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">location</var>, </td></tr><tr><td> </td><td>GLint *<var class="pdparam">params</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>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"><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 class="citerefentry" 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"><a id="notes"></a><h2>Notes</h2><p><code class="function">glGetUniform</code> is available only if the
	GL version is 2.0 or greater.</p><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"><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><p><code class="constant">GL_INVALID_OPERATION</code> is generated if
	<code class="function">glGetUniform</code> is executed between the
	execution of
	<a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
	and the corresponding execution of
	<a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.</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="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 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="glCreateProgram.xml"><span class="citerefentry"><span class="refentrytitle">glCreateProgram</span></span></a>,
	<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. 
            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>