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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>glTransformFeedbackVaryings</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div class="refentry" title="glTransformFeedbackVaryings"><a id="glTransformFeedbackVaryings"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glTransformFeedbackVaryings — specify values to record in transform feedback buffers</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTransformFeedbackVaryings</b>(</code></td><td>GLuint<var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLsizei<var class="pdparam">count</var>, </td></tr><tr><td> </td><td>const char **<var class="pdparam">varyings</var>, </td></tr><tr><td> </td><td>GLenum<var class="pdparam">bufferMode</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><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>
                    The name of the target program object.
                </p></dd><dt><span class="term"><em class="parameter"><code>count</code></em></span></dt><dd><p>
                    The number of varying variables used for transform feedback.
                </p></dd><dt><span class="term"><em class="parameter"><code>varyings</code></em></span></dt><dd><p>
                    An array of <em class="parameter"><code>count</code></em> zero-terminated strings specifying the
                    names of the varying variables to use for transform feedback.
                </p></dd><dt><span class="term"><em class="parameter"><code>bufferMode</code></em></span></dt><dd><p>
                    Identifies the mode used to capture the varying variables when transform feedback is active.
                    <em class="parameter"><code>bufferMode</code></em> must be <code class="constant">GL_INTERLEAVED_ATTRIBS</code> or <code class="constant">GL_SEPARATE_ATTRIBS</code>.
                </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>
            The names of the vertex or geometry shader outputs to be recorded in transform feedback mode
            are specified using <code class="function">glTransformFeedbackVaryings</code>. When a geometry shader
            is active, transform feedback records the values of selected geometry shader output variables
            from the emitted vertices. Otherwise, the values of the selected vertex shader outputs are
            recorded.
        </p><p>
            The state set by <code class="function">glTranformFeedbackVaryings</code> is stored and takes effect
            next time <a class="citerefentry" href="glLinkProgram.xml"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a> is called
            on <em class="parameter"><code>program</code></em>. When <a class="citerefentry" href="glLinkProgram.xml"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>
            is called, <em class="parameter"><code>program</code></em> is linked so that the values of the specified varying variables
            for the vertices of each primitive generated by the GL are written to a single buffer
            object if <em class="parameter"><code>bufferMode</code></em> is <code class="constant">GL_INTERLEAVED_ATTRIBS</code> or multiple
            buffer objects if <em class="parameter"><code>bufferMode</code></em> is <code class="constant">GL_SEPARATE_ATTRIBS</code>.
        </p><p>
            In addition to the errors generated by <code class="function">glTransformFeedbackVaryings</code>, the
            program <em class="parameter"><code>program</code></em> will fail to link if:
            </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
                        The count specified by <code class="function">glTransformFeedbackVaryings</code> is non-zero, but the
                        program object has no vertex or geometry shader.
                    </p></li><li class="listitem"><p>
                        Any variable name specified in the <em class="parameter"><code>varyings</code></em> array is not declared as an output
                        in the vertex shader (or the geometry shader, if active).
                    </p></li><li class="listitem"><p>
                        Any two entries in the <em class="parameter"><code>varyings</code></em> array specify the same varying variable.
                    </p></li><li class="listitem"><p>
                        The total number of components to capture in any varying variable in <em class="parameter"><code>varyings</code></em>
                        is greater than the constant <code class="constant">GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS</code>
                        and the buffer mode is <code class="constant">GL_SEPARATE_ATTRIBS</code>.
                    </p></li><li class="listitem"><p>
                        The total number of components to capture is greater than the constant
                        <code class="constant">GL_MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS</code> and the buffer
                        mode is <code class="constant">GL_INTERLEAVED_ATTRIBS</code>.
                    </p></li></ul></div><p>
        </p></div><div class="refsect1" title="Notes"><a id="notes"></a><h2>Notes</h2><p>
            <code class="function">glGetTransformFeedbackVarying</code> is available only if the GL version is 3.0 or greater.
        </p></div><div class="refsect1" title="Errors"><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
            the name of a program object.
        </p><p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>bufferMode</code></em> is <code class="constant">GL_SEPARATE_ATTRIBS</code>
            and <em class="parameter"><code>count</code></em> is greater than the implementation-dependent limit <code class="constant">GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS</code>.
        </p></div><div class="refsect1" title="Associated Gets"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a class="citerefentry" href="glGetTransformFeedbackVarying.xml"><span class="citerefentry"><span class="refentrytitle">glGetTransformFeedbackVarying</span></span></a>
        </p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glBeginTransformFeedback.xml"><span class="citerefentry"><span class="refentrytitle">glBeginTransformFeedback</span></span></a>,
            <a class="citerefentry" href="glEndTransformFeedback.xml"><span class="citerefentry"><span class="refentrytitle">glEndTransformFeedback</span></span></a>,
            <a class="citerefentry" href="glGetTransformFeedbackVarying.xml"><span class="citerefentry"><span class="refentrytitle">glGetTransformFeedbackVarying</span></span></a>
        </p></div><div class="refsect1" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 2010 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>
