2013-10-10 23:58:54 +00:00
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glTransformFeedbackVaryings">
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2013-11-03 11:43:50 +00:00
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<refentryinfo>
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<copyright>
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<year>2010-2013</year>
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<holder>Khronos Group</holder>
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</copyright>
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</refentryinfo>
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2013-10-10 23:58:54 +00:00
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<refmeta>
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<refentrytitle>glTransformFeedbackVaryings</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glTransformFeedbackVaryings</refname>
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<refpurpose>specify values to record in transform feedback buffers</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTransformFeedbackVaryings</function></funcdef>
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<paramdef>GLuint<parameter>program</parameter></paramdef>
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<paramdef>GLsizei<parameter>count</parameter></paramdef>
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<paramdef>const char **<parameter>varyings</parameter></paramdef>
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<paramdef>GLenum<parameter>bufferMode</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>program</parameter></term>
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<listitem>
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<para>
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The name of the target program object.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>count</parameter></term>
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<listitem>
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<para>
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The number of varying variables used for transform feedback.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>varyings</parameter></term>
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<listitem>
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<para>
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An array of <parameter>count</parameter> zero-terminated strings specifying the
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names of the varying variables to use for transform feedback.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>bufferMode</parameter></term>
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<listitem>
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<para>
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Identifies the mode used to capture the varying variables when transform feedback is active.
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<parameter>bufferMode</parameter> must be <constant>GL_INTERLEAVED_ATTRIBS</constant> or <constant>GL_SEPARATE_ATTRIBS</constant>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para>
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The names of the vertex or geometry shader outputs to be recorded in transform feedback mode
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are specified using <function>glTransformFeedbackVaryings</function>. When a geometry shader
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is active, transform feedback records the values of selected geometry shader output variables
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from the emitted vertices. Otherwise, the values of the selected vertex shader outputs are
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recorded.
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</para>
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<para>
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The state set by <function>glTranformFeedbackVaryings</function> is stored and takes effect
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next time <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> is called
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on <parameter>program</parameter>. When <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>
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is called, <parameter>program</parameter> is linked so that the values of the specified varying variables
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for the vertices of each primitive generated by the GL are written to a single buffer
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object if <parameter>bufferMode</parameter> is <constant>GL_INTERLEAVED_ATTRIBS</constant> or multiple
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buffer objects if <parameter>bufferMode</parameter> is <constant>GL_SEPARATE_ATTRIBS</constant>.
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</para>
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<para>
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In addition to the errors generated by <function>glTransformFeedbackVaryings</function>, the
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program <parameter>program</parameter> will fail to link if:
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<itemizedlist>
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<listitem>
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<para>
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The count specified by <function>glTransformFeedbackVaryings</function> is non-zero, but the
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program object has no vertex or geometry shader.
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</para>
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</listitem>
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<listitem>
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<para>
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Any variable name specified in the <parameter>varyings</parameter> array is not declared as an output
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in the vertex shader (or the geometry shader, if active).
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</para>
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</listitem>
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<listitem>
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<para>
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Any two entries in the <parameter>varyings</parameter> array specify the same varying variable.
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</para>
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</listitem>
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<listitem>
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<para>
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The total number of components to capture in any varying variable in <parameter>varyings</parameter>
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is greater than the constant <constant>GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS</constant>
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and the buffer mode is <constant>GL_SEPARATE_ATTRIBS</constant>.
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</para>
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</listitem>
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<listitem>
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<para>
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The total number of components to capture is greater than the constant
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<constant>GL_MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS</constant> and the buffer
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mode is <constant>GL_INTERLEAVED_ATTRIBS</constant>.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</refsect1>
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<refsect1 id="notes"><title>Notes</title>
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<para>
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<function>glGetTransformFeedbackVarying</function> is available only if the GL version is 3.0 or greater.
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</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para>
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<constant>GL_INVALID_VALUE</constant> is generated if <parameter>program</parameter> is not
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the name of a program object.
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</para>
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<para>
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<constant>GL_INVALID_VALUE</constant> is generated if <parameter>bufferMode</parameter> is <constant>GL_SEPARATE_ATTRIBS</constant>
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and <parameter>count</parameter> is greater than the implementation-dependent limit <constant>GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS</constant>.
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</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para>
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<citerefentry><refentrytitle>glGetTransformFeedbackVarying</refentrytitle></citerefentry>
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</para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para>
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<citerefentry><refentrytitle>glBeginTransformFeedback</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glEndTransformFeedback</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glGetTransformFeedbackVarying</refentrytitle></citerefentry>
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</para>
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</refsect1> <refsect1 id="Copyright"><title>Copyright</title>
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<para>
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2013-11-03 11:43:50 +00:00
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Copyright <trademark class="copyright"></trademark> 2010-2013 Khronos Group.
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This material may be distributed subject to the terms and conditions set forth in
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2013-10-10 23:58:54 +00:00
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the Open Publication License, v 1.0, 8 June 1999.
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<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
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</para>
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</refsect1>
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</refentry>
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