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<!DOCTYPE refentry [ <!ENTITY % mathent SYSTEM "math.ent"> %mathent; ]>
<!-- Converted by db4-upgrade version 1.1 -->
<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glGetUniform">
<info>
<copyright>
<year>2003-2005</year>
<holder>3Dlabs Inc. Ltd.</holder>
</copyright>
<copyright>
<year>2010-2014</year>
<holder>Khronos Group</holder>
</copyright>
</info>
<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>
<funcprototype>
<funcdef>void <function>glGetUniformuiv</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLint <parameter>location</parameter></paramdef>
<paramdef>GLuint *<parameter>params</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>glGetUniformdv</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLint <parameter>location</parameter></paramdef>
<paramdef>GLdouble *<parameter>params</parameter></paramdef>
</funcprototype>
<!-- robustness commands -->
<funcprototype>
<funcdef>void <function>glGetnUniformfv</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLint <parameter>location</parameter></paramdef>
<paramdef>GLsizei <parameter>bufSize</parameter></paramdef>
<paramdef>GLfloat *<parameter>params</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>glGetnUniformiv</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLint <parameter>location</parameter></paramdef>
<paramdef>GLsizei <parameter>bufSize</parameter></paramdef>
<paramdef>GLint *<parameter>params</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>glGetnUniformuiv</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLint <parameter>location</parameter></paramdef>
<paramdef>GLsizei <parameter>bufSize</parameter></paramdef>
<paramdef>GLuint *<parameter>params</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>glGetnUniformdv</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLint <parameter>location</parameter></paramdef>
<paramdef>GLsizei <parameter>bufSize</parameter></paramdef>
<paramdef>GLdouble *<parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 xml: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>bufSize</parameter></term>
<listitem>
<para>Specifies the size of the buffer
<parameter>params</parameter>.</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 xml:id="description">
<title>Description</title>
<para><function>glGetUniform</function> and
<function>glGetnUniform</function> return 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> or <function>glGetnUniform</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>
<para>The only difference between <function>glGetUniform</function> and
<function>glGetnUniform</function> is that
<function>glGetnUniform</function> will generate an error if size of the
<parameter>params</parameter> buffer,as described by
<parameter>bufSize</parameter>, is not large enough to hold the result
data.</para>
</refsect1>
<refsect1 xml:id="notes">
<title>Notes</title>
<para>If an error is generated, no change is made to the contents of
<parameter>params</parameter>.</para>
</refsect1>
<refsect1 xml: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 by
<function>glGetnUniform</function> if the buffer size required to store
the requested data is greater than <parameter>bufSize</parameter>.</para>
</refsect1>
<refsect1 xml: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 xml:id="versions"><title>Version Support</title>
<informaltable>
<tgroup cols="13" align="left">
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
<tbody>
<row>
<entry><function>glGetUniformdv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='40']/*)"/>
</row>
<row>
<entry><function>glGetUniformfv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='20']/*)"/>
</row>
<row>
<entry><function>glGetUniformiv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='20']/*)"/>
</row>
<row>
<entry><function>glGetUniformuiv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='30']/*)"/>
</row>
<row>
<entry><function>glGetnUniformdv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='45']/*)"/>
</row>
<row>
<entry><function>glGetnUniformfv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='45']/*)"/>
</row>
<row>
<entry><function>glGetnUniformiv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='45']/*)"/>
</row>
<row>
<entry><function>glGetnUniformuiv</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='45']/*)"/>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 xml: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 xml:id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"/> 2003-2005 3Dlabs Inc. Ltd.
Copyright <trademark class="copyright"/> 2010-2014 Khronos Group.
This material may be distributed subject to the terms and conditions set forth in
the Open Publication License, v 1.0, 8 June 1999.
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://opencontent.org/openpub/">http://opencontent.org/openpub/</link>.
</para>
</refsect1>
</refentry>
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