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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
<?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 4 Reference Pages</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><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glGetUniformuiv</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>GLuint *<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">glGetUniformdv</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>GLdouble *<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>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></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.
Copyright <span class="trademark"></span>© 2010-2013 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.
<a class="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p></div></div></body></html>
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