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<refentry id="glGetUniform">
    <refmeta>
	<refentrytitle>glGetUniform</refentrytitle>
	<manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
	<refdescriptor>glGetUniform</refdescriptor>
	<refname>glGetUniformfv</refname>
	<refname>glGetUniformiv</refname>
	<refpurpose>Returns the value of a uniform variable</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
	<funcsynopsis>
	    <funcprototype>
		<funcdef>void <function>glGetUniformfv</function></funcdef>
		<paramdef>GLuint <parameter>program</parameter></paramdef>
		<paramdef>GLint <parameter>location</parameter></paramdef>
		<paramdef>GLfloat *<parameter>params</parameter></paramdef>
	    </funcprototype>
	    <funcprototype>
		<funcdef>void <function>glGetUniformiv</function></funcdef>
		<paramdef>GLuint <parameter>program</parameter></paramdef>
		<paramdef>GLint <parameter>location</parameter></paramdef>
		<paramdef>GLint *<parameter>params</parameter></paramdef>
	    </funcprototype>
	</funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
	<variablelist>
	    <varlistentry>
		<term><parameter>program</parameter></term>
		<listitem>
		    <para>Specifies the program object to be
		    queried.</para>
		</listitem>
	    </varlistentry>
	    <varlistentry>
		<term><parameter>location</parameter></term>
		<listitem>
		    <para>Specifies the location of the uniform variable
		    to be queried.</para>
		</listitem>
	    </varlistentry>
	    <varlistentry>
		<term><parameter>params</parameter></term>
		<listitem>
		    <para>Returns the value of the specified uniform
		    variable.</para>
		</listitem>
	    </varlistentry>
	</variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
	<para><function>glGetUniform</function> returns in
	<parameter>params</parameter> the value(s) of the specified
	uniform variable. The type of the uniform variable specified by
	<parameter>location</parameter> 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
	<function>glGetUniform</function> for each element of the array.
	To query values stored in uniform variables declared as
	structures, call <function>glGetUniform</function> for each
	field in the structure. The values for uniform variables
	declared as a matrix will be returned in column major
	order.</para>

	<para>The locations assigned to uniform variables are not known
	until the program object is linked. After linking has occurred,
	the command
	<citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry>
	can be used to obtain the location of a uniform variable. This
	location value can then be passed to
	<function>glGetUniform</function> 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.</para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
	<para><function>glGetUniform</function> is available only if the
	GL version is 2.0 or greater.</para>

	<para>If an error is generated, no change is made to the
	contents of <parameter>params</parameter>.</para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
	<para><constant>GL_INVALID_VALUE</constant> is generated if
	<parameter>program</parameter> is not a value generated by
	OpenGL.</para>

	<para><constant>GL_INVALID_OPERATION</constant> is generated if
	<parameter>program</parameter> is not a program object.</para>

	<para><constant>GL_INVALID_OPERATION</constant> is generated if
	<parameter>program</parameter> has not been successfully
	linked.</para>

	<para><constant>GL_INVALID_OPERATION</constant> is generated if
	<parameter>location</parameter> does not correspond to a valid
	uniform variable location for the specified program object.</para>

	<para><constant>GL_INVALID_OPERATION</constant> is generated if
	<function>glGetUniform</function> is executed between the
	execution of
	<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
	and the corresponding execution of
	<citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.</para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
	<para><citerefentry><refentrytitle>glGetActiveUniform</refentrytitle></citerefentry>
	with arguments <parameter>program</parameter> and the index of an active
	uniform variable</para>

	<para><citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry>
	with arguments <parameter>program</parameter> and
	<constant>GL_ACTIVE_UNIFORMS</constant> or
	<constant>GL_ACTIVE_UNIFORM_MAX_LENGTH</constant></para>

	<para><citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry>
	with arguments <parameter>program</parameter> and the name of a
	uniform variable</para>
	<para><citerefentry><refentrytitle>glIsProgram</refentrytitle></citerefentry></para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
	<para><citerefentry><refentrytitle>glCreateProgram</refentrytitle></citerefentry>,
	<citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>,
	<citerefentry><refentrytitle>glUniform</refentrytitle></citerefentry></para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 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.
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
        </para>
    </refsect1>
</refentry>
