'\" t
.\"     Title: glBeginTransformFeedback
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets v1.79.2 <http://docbook.sf.net/>
.\"      Date: 05/21/2022
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
.\"
.TH "GLBEGINTRANSFORMFEED" "3G" "05/21/2022" "[FIXME: source]" "[FIXME: manual]"
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.nh
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.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
glBeginTransformFeedback \- start transform feedback operation
.SH "C SPECIFICATION"
.HP \w'void\ glBeginTransformFeedback('u
.BI "void glBeginTransformFeedback(GLenum\ " "primitiveMode" ");"
.HP \w'void\ glEndTransformFeedback('u
.BI "void glEndTransformFeedback(" "void" ");"
.SH "PARAMETERS FOR GLBEGINTRANSFORMFEEDBACK"
.PP
\fIprimitiveMode\fR
.RS 4
Specify the output type of the primitives that will be recorded into the buffer objects that are bound for transform feedback\&.
.RE
.SH "DESCRIPTION"
.PP
Transform feedback mode captures the values of varying variables written by the vertex shader (or, if active, the geometry shader)\&. Transform feedback is said to be active after a call to
\fBglBeginTransformFeedback\fR
until a subsequent call to

\fBglEndTransformFeedback\fR\&. Transform feedback commands must be paired\&.
.PP
If no geometry shader is present, while transform feedback is active the
\fImode\fR
parameter to
\fBglDrawArrays\fR()
must match those specified in the following table:
.TS
allbox tab(:);
lB lB.
T{
\fB 
                                Transform Feedback \fR\fB\fIprimitiveMode\fR\fR\fB
                            \fR
T}:T{
\fB 
                                Allowed Render Primitive \fR\fB\fImodes\fR\fR\fB
                            \fR
T}
.T&
l l
l l
l l.
T{
\fBGL_POINTS\fR
T}:T{
\fBGL_POINTS\fR
T}
T{
\fBGL_LINES\fR
T}:T{
\fBGL_LINES\fR,
                            \fBGL_LINE_LOOP\fR,
                            \fBGL_LINE_STRIP\fR,
                            \fBGL_LINES_ADJACENCY\fR,
                            \fBGL_LINE_STRIP_ADJACENCY\fR
T}
T{
\fBGL_TRIANGLES\fR
T}:T{
\fBGL_TRIANGLES\fR, 
                            \fBGL_TRIANGLE_STRIP\fR, 
                            \fBGL_TRIANGLE_FAN\fR,
                            \fBGL_TRIANGLES_ADJACENCY\fR, 
                            \fBGL_TRIANGLE_STRIP_ADJACENCY\fR
T}
.TE
.sp 1
.PP
If a geometry shader is present, the output primitive type from the geometry shader must match those provided in the following table:
.TS
allbox tab(:);
lB lB.
T{
\fB
                                Transform Feedback \fR\fB\fIprimitiveMode\fR\fR\fB
                            \fR
T}:T{
\fB
                                Allowed Geometry Shader Output Primitive Type
                            \fR
T}
.T&
l l
l l
l l.
T{
\fBGL_POINTS\fR
T}:T{
\fBpoints\fR
T}
T{
\fBGL_LINES\fR
T}:T{
\fBline_strip\fR
T}
T{
\fBGL_TRIANGLES\fR
T}:T{
\fBtriangle_strip\fR
T}
.TE
.sp 1
.SH "NOTES"
.PP
Geometry shaders, and the
\fBGL_TRIANGLES_ADJACENCY\fR,
\fBGL_TRIANGLE_STRIP_ADJACENCY\fR,
\fBGL_LINES_ADJACENCY\fR
and
\fBGL_LINE_STRIP_ADJACENCY\fR
primtive modes are available only if the GL version is 3\&.2 or greater\&.
.SH "ERRORS"
.PP
\fBGL_INVALID_OPERATION\fR
is generated if
\fBglBeginTransformFeedback\fR
is executed while transform feedback is active\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if
\fBglEndTransformFeedback\fR
is executed while transform feedback is not active\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated by
\fBglDrawArrays\fR()
if no geometry shader is present, transform feedback is active and
\fImode\fR
is not one of the allowed modes\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated by
\fBglDrawArrays\fR()
if a geometry shader is present, transform feedback is active and the output primitive type of the geometry shader does not match the transform feedback
\fIprimitiveMode\fR\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated by
\fBglBeginTransformFeedback\fR
if any binding point used in transform feedback mode does not have a buffer object bound\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated by
\fBglBeginTransformFeedback\fR
if no binding points would be used, either because no program object is active of because the active program object has specified no varying variables to record\&.
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Version\fR
T}
T{
\fBFunction / Feature Name\fR
T}:T{
\fB2\&.0\fR
T}:T{
\fB2\&.1\fR
T}:T{
\fB3\&.0\fR
T}:T{
\fB3\&.1\fR
T}:T{
\fB3\&.2\fR
T}:T{
\fB3\&.3\fR
T}:T{
\fB4\&.0\fR
T}:T{
\fB4\&.1\fR
T}:T{
\fB4\&.2\fR
T}:T{
\fB4\&.3\fR
T}:T{
\fB4\&.4\fR
T}:T{
\fB4\&.5\fR
T}
.T&
l c c c c c c c c c c c c
l c c c c c c c c c c c c.
T{
\fBglBeginTransformFeedback\fR
T}:T{
\-
T}:T{
\-
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}
T{
\fBglEndTransformFeedback\fR
T}:T{
\-
T}:T{
\-
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}
.TE
.sp 1
.SH "SEE ALSO"
.SH "COPYRIGHT"
.PP
Copyright
\(co
2010\-2014 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\&.
\m[blue]\fBhttp://opencontent\&.org/openpub/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 2010-2014 Khronos Group
.br