upstream-man-pages/man4/glTransformFeedbackVaryings.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glTransformFeedbackVaryings">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2010</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glTransformFeedbackVaryings</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glTransformFeedbackVaryings</refname>
  17         <refpurpose>specify values to record in transform feedback buffers</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glTransformFeedbackVaryings</function></funcdef>
  23                 <paramdef>GLuint<parameter>program</parameter></paramdef>
  24                 <paramdef>GLsizei<parameter>count</parameter></paramdef>
  25                 <paramdef>const char **<parameter>varyings</parameter></paramdef>
  26                 <paramdef>GLenum<parameter>bufferMode</parameter></paramdef>
  27             </funcprototype>
  28         </funcsynopsis>
  29     </refsynopsisdiv>
  30     <refsect1 id="parameters"><title>Parameters</title>
  31         <variablelist>
  32         <varlistentry>
  33             <term><parameter>program</parameter></term>
  34             <listitem>
  35                 <para>
  36                     The name of the target program object.
  37                 </para>
  38             </listitem>
  39         </varlistentry>
  40         <varlistentry>
  41             <term><parameter>count</parameter></term>
  42             <listitem>
  43                 <para>
  44                     The number of varying variables used for transform feedback.
  45                 </para>
  46             </listitem>
  47         </varlistentry>
  48         <varlistentry>
  49             <term><parameter>varyings</parameter></term>
  50             <listitem>
  51                 <para>
  52                     An array of <parameter>count</parameter> zero-terminated strings specifying the
  53                     names of the varying variables to use for transform feedback.
  54                 </para>
  55             </listitem>
  56         </varlistentry>
  57         <varlistentry>
  58             <term><parameter>bufferMode</parameter></term>
  59             <listitem>
  60                 <para>
  61                     Identifies the mode used to capture the varying variables when transform feedback is active.
  62                     <parameter>bufferMode</parameter> must be <constant>GL_INTERLEAVED_ATTRIBS</constant> or <constant>GL_SEPARATE_ATTRIBS</constant>.
  63                 </para>
  64             </listitem>
  65         </varlistentry>
  66         </variablelist>
  67     </refsect1>
  68     <refsect1 id="description"><title>Description</title>
  69         <para>
  70             The names of the vertex or geometry shader outputs to be recorded in transform feedback mode
  71             are specified using <function>glTransformFeedbackVaryings</function>. When a geometry shader
  72             is active, transform feedback records the values of selected geometry shader output variables
  73             from the emitted vertices. Otherwise, the values of the selected vertex shader outputs are
  74             recorded.
  75         </para>
  76         <para>
  77             The state set by <function>glTranformFeedbackVaryings</function> is stored and takes effect
  78             next time <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> is called
  79             on <parameter>program</parameter>. When <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>
  80             is called, <parameter>program</parameter> is linked so that the values of the specified varying variables
  81             for the vertices of each primitive generated by the GL are written to a single buffer
  82             object if <parameter>bufferMode</parameter> is <constant>GL_INTERLEAVED_ATTRIBS</constant> or multiple
  83             buffer objects if <parameter>bufferMode</parameter> is <constant>GL_SEPARATE_ATTRIBS</constant>.
  84         </para>
  85         <para>
  86             In addition to the errors generated by <function>glTransformFeedbackVaryings</function>, the
  87             program <parameter>program</parameter> will fail to link if:
  88             <itemizedlist>
  89                 <listitem>
  90                     <para>
  91                         The count specified by <function>glTransformFeedbackVaryings</function> is non-zero, but the
  92                         program object has no vertex or geometry shader.
  93                     </para>
  94                 </listitem>
  95                 <listitem>
  96                     <para>
  97                         Any variable name specified in the <parameter>varyings</parameter> array is not declared as an output
  98                         in the vertex shader (or the geometry shader, if active).
  99                     </para>
 100                 </listitem>
 101                 <listitem>
 102                     <para>
 103                         Any two entries in the <parameter>varyings</parameter> array specify the same varying variable.
 104                     </para>
 105                 </listitem>
 106                 <listitem>
 107                     <para>
 108                         The total number of components to capture in any varying variable in <parameter>varyings</parameter>
 109                         is greater than the constant <constant>GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS</constant>
 110                         and the buffer mode is <constant>GL_SEPARATE_ATTRIBS</constant>.
 111                     </para>
 112                 </listitem>
 113                 <listitem>
 114                     <para>
 115                         The total number of components to capture is greater than the constant
 116                         <constant>GL_MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS</constant> and the buffer
 117                         mode is <constant>GL_INTERLEAVED_ATTRIBS</constant>.
 118                     </para>
 119                 </listitem>
 120             </itemizedlist>
 121         </para>
 122     </refsect1>
 123     <refsect1 id="notes"><title>Notes</title>
 124         <para>
 125             <function>glGetTransformFeedbackVarying</function> is available only if the GL version is 3.0 or greater.
 126         </para>
 127     </refsect1>
 128     <refsect1 id="errors"><title>Errors</title>
 129         <para>
 130             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>program</parameter> is not
 131             the name of a program object.
 132         </para>
 133         <para>
 134             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>bufferMode</parameter> is <constant>GL_SEPARATE_ATTRIBS</constant>
 135             and <parameter>count</parameter> is greater than the implementation-dependent limit <constant>GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS</constant>.
 136         </para>
 137     </refsect1>
 138         <refsect1 id="associatedgets"><title>Associated Gets</title>
 139         <para>
 140             <citerefentry><refentrytitle>glGetTransformFeedbackVarying</refentrytitle></citerefentry>
 141         </para>
 142     </refsect1>
 143     <refsect1 id="seealso"><title>See Also</title>
 144         <para>
 145             <citerefentry><refentrytitle>glBeginTransformFeedback</refentrytitle></citerefentry>,
 146             <citerefentry><refentrytitle>glEndTransformFeedback</refentrytitle></citerefentry>,
 147             <citerefentry><refentrytitle>glGetTransformFeedbackVarying</refentrytitle></citerefentry>
 148         </para>
 149     </refsect1>    <refsect1 id="Copyright"><title>Copyright</title>
 150         <para>
 151             Copyright <trademark class="copyright"></trademark> 2010 Khronos Group.
 152             This material may be distributed subject to the terms and conditions set forth in
 153             the Open Publication License, v 1.0, 8 June 1999.
 154             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 155         </para>
 156     </refsect1>
 157 </refentry>