1 <?xml version=
"1.0" encoding=
"UTF-8"?>
2 <!DOCTYPE html PUBLIC
"-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
3 <!-- saved from url=(0013)about:internet -->
4 <?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>glBeginTransformFeedback - OpenGL
4 Reference Pages
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.69.1" /></head><body><div class=
"refentry" lang=
"en" xml:
lang=
"en"><a id=
"glBeginTransformFeedback"></a><div class=
"titlepage"></div><div class=
"refnamediv"><h2>Name
</h2><p>glBeginTransformFeedback — start transform feedback operation
</p></div><div class=
"refsynopsisdiv"><h2>C Specification
</h2><div class=
"funcsynopsis"><table border=
"0" summary=
"Function synopsis" cellspacing=
"0" cellpadding=
"0"><tr><td><code class=
"funcdef">void
<b class=
"fsfunc">glBeginTransformFeedback
</b>(
</code></td><td>GLenum
</td><td><var class=
"pdparam">primitiveMode
</var><code>)
</code>;
</td></tr></table></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"parameters"></a><h2>Parameters
</h2><div class=
"variablelist"><dl><dt><span class=
"term"><em class=
"parameter"><code>primitiveMode
</code></em></span></dt><dd><p>
5 Specify the output type of the primitives that will be recorded into the
6 buffer objects that are bound for transform feedback.
7 </p></dd></dl></div></div><div class=
"refsynopsisdiv"><h2>C Specification
</h2><div class=
"funcsynopsis"><p><code class=
"funcdef">void
<b class=
"fsfunc">glEndTransformFeedback
</b>(
</code><var class=
"pdparam">void
</var><code>)
</code>;
</p></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
8 Transform feedback mode captures the values of varying variables written by the vertex shader (or, if active, the geometry shader).
9 Transform feedback is said to be active after a call to
<code class=
"function">glBeginTransformFeedback
</code>
10 until a subsequent call to
<a href=
"glEndTransformFeedback.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glEndTransformFeedback
</span></span></a>.
11 Transform feedback commands must be paired.
13 If no geometry shader is present, while transform feedback is active the
<em class=
"parameter"><code>mode
</code></em> parameter to
14 <a href=
"glDrawArrays.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawArrays
</span></span></a> must match those specified
15 in the following table:
16 </p><div class=
"informaltable"><table border=
"1"><colgroup><col align=
"left" /><col align=
"left" /></colgroup><thead><tr><th align=
"left"><span class=
"bold"><strong>
17 Transform Feedback
<em class=
"parameter"><code>primitiveMode
</code></em>
18 </strong></span></th><th align=
"left"><span class=
"bold"><strong>
19 Allowed Render Primitive
<em class=
"parameter"><code>modes
</code></em>
20 </strong></span></th></tr></thead><tbody><tr><td align=
"left">
21 <code class=
"constant">GL_POINTS
</code>
22 </td><td align=
"left">
23 <code class=
"constant">GL_POINTS
</code>
24 </td></tr><tr><td align=
"left">
25 <code class=
"constant">GL_LINES
</code>
26 </td><td align=
"left">
27 <code class=
"constant">GL_LINES
</code>,
<code class=
"constant">GL_LINE_LOOP
</code>,
<code class=
"constant">GL_LINE_STRIP
</code>,
28 <code class=
"constant">GL_LINES_ADJACENCY
</code>,
<code class=
"constant">GL_LINE_STRIP_ADJACENCY
</code>
29 </td></tr><tr><td align=
"left">
30 <code class=
"constant">GL_TRIANGLES
</code>
31 </td><td align=
"left">
32 <code class=
"constant">GL_TRIANGLES
</code>,
<code class=
"constant">GL_TRIANGLE_STRIP
</code>,
<code class=
"constant">GL_TRIANGLE_FAN
</code>,
33 <code class=
"constant">GL_TRIANGLES_ADJACENCY
</code>,
<code class=
"constant">GL_TRIANGLE_STRIP_ADJACENCY
</code>
34 </td></tr></tbody></table></div><p>
35 If a geometry shader is present, the output primitive type from the geometry shader must match those
36 provided in the following table:
37 </p><div class=
"informaltable"><table border=
"1"><colgroup><col align=
"left" /><col align=
"left" /></colgroup><thead><tr><th align=
"left"><span class=
"bold"><strong>
38 Transform Feedback
<em class=
"parameter"><code>primitiveMode
</code></em>
39 </strong></span></th><th align=
"left"><span class=
"bold"><strong>
40 Allowed Geometry Shader Output Primitive Type
41 </strong></span></th></tr></thead><tbody><tr><td align=
"left">
42 <code class=
"constant">GL_POINTS
</code>
43 </td><td align=
"left">
44 <code class=
"constant">points
</code>
45 </td></tr><tr><td align=
"left">
46 <code class=
"constant">GL_LINES
</code>
47 </td><td align=
"left">
48 <code class=
"constant">line_strip
</code>
49 </td></tr><tr><td align=
"left">
50 <code class=
"constant">GL_TRIANGLES
</code>
51 </td><td align=
"left">
52 <code class=
"constant">triangle_strip
</code>
53 </td></tr></tbody></table></div><p>
54 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"notes"></a><h2>Notes
</h2><p>
55 Geometry shaders, and the
<code class=
"constant">GL_TRIANGLES_ADJACENCY
</code>,
<code class=
"constant">GL_TRIANGLE_STRIP_ADJACENCY
</code>,
56 <code class=
"constant">GL_LINES_ADJACENCY
</code> and
<code class=
"constant">GL_LINE_STRIP_ADJACENCY
</code> primtive modes are available
57 only if the GL version is
3.2 or greater.
58 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"errors"></a><h2>Errors
</h2><p>
59 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated if
<code class=
"function">glBeginTransformFeedback
</code> is executed
60 while transform feedback is active.
62 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated if
<code class=
"function">glEndTransformFeedback
</code> is executed
63 while transform feedback is not active.
65 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated by
<a href=
"glDrawArrays.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawArrays
</span></span></a>
66 if no geometry shader is present, transform feedback is active and
<em class=
"parameter"><code>mode
</code></em> is not one of the allowed modes.
68 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated by
<a href=
"glDrawArrays.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawArrays
</span></span></a>
69 if a geometry shader is present, transform feedback is active and the output primitive type of the geometry shader does not
70 match the transform feedback
<em class=
"parameter"><code>primitiveMode
</code></em>.
72 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated by
<code class=
"function">glEndTransformFeedback
</code> if any binding
73 point used in transform feedback mode does not have a buffer object bound.
75 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated by
<code class=
"function">glEndTransformFeedback
</code> if no binding
76 points would be used, either because no program object is active of because the active program object has specified
77 no varying variables to record.
78 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
79 Copyright
<span class=
"trademark"></span>©
2010 Khronos Group.
80 This material may be distributed subject to the terms and conditions set forth in
81 the Open Publication License, v
1.0,
8 June
1999.
82 <a href=
"http://opencontent.org/openpub/" target=
"_top">http://opencontent.org/openpub/
</a>.
83 </p></div></div></body></html>