GLBEGINTRANSFORMFEED(3G) [FIXME: manual] GLBEGINTRANSFORMFEED(3G)
NAME
glBeginTransformFeedback - start transform feedback operation
C SPECIFICATION
void glBeginTransformFeedback(GLenum primitiveMode);
PARAMETERS
primitiveMode
Specify the output type of the primitives that will be recorded into the buffer objects that are bound for transform feedback.
C SPECIFICATION
void glEndTransformFeedback(void);
DESCRIPTION
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 glBeginTransformFeedback until a subsequent call to glEndTransformFeedback().
Transform feedback commands must be paired.
If no geometry shader is present, while transform feedback is active the mode parameter to glDrawArrays() must match those specified in the
following table:
+-------------------------------------------+---------------------------------------------------+
| | |
| Transform Feedback | Allowed Render Primitive |
|primitiveMode | modes |
| | |
+-------------------------------------------+---------------------------------------------------+
|GL_POINTS | GL_POINTS |
+-------------------------------------------+---------------------------------------------------+
|GL_LINES | GL_LINES, GL_LINE_LOOP, GL_LINE_STRIP, |
| | GL_LINES_ADJACENCY, |
| | GL_LINE_STRIP_ADJACENCY |
+-------------------------------------------+---------------------------------------------------+
|GL_TRIANGLES | GL_TRIANGLES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, |
| | GL_TRIANGLES_ADJACENCY, |
| | GL_TRIANGLE_STRIP_ADJACENCY |
+-------------------------------------------+---------------------------------------------------+
If a geometry shader is present, the output primitive type from the geometry shader must match those provided in the following table:
+-------------------------------------------+-------------------------------------------------+
| | |
| Transform Feedback | Allowed Geometry Shader |
|primitiveMode | Output Primitive Type |
| | |
+-------------------------------------------+-------------------------------------------------+
|GL_POINTS | points |
+-------------------------------------------+-------------------------------------------------+
|GL_LINES | line_strip |
+-------------------------------------------+-------------------------------------------------+
|GL_TRIANGLES | triangle_strip |
+-------------------------------------------+-------------------------------------------------+
NOTES
Geometry shaders, and the GL_TRIANGLES_ADJACENCY, GL_TRIANGLE_STRIP_ADJACENCY, GL_LINES_ADJACENCY and GL_LINE_STRIP_ADJACENCY primtive
modes are available only if the GL version is 3.2 or greater.
ERRORS
GL_INVALID_OPERATION is generated if glBeginTransformFeedback is executed while transform feedback is active.
GL_INVALID_OPERATION is generated if glEndTransformFeedback is executed while transform feedback is not active.
GL_INVALID_OPERATION is generated by glDrawArrays() if no geometry shader is present, transform feedback is active and mode is not one of
the allowed modes.
GL_INVALID_OPERATION is generated by glDrawArrays() 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 primitiveMode.
GL_INVALID_OPERATION is generated by glEndTransformFeedback if any binding point used in transform feedback mode does not have a buffer
object bound.
GL_INVALID_OPERATION is generated by glEndTransformFeedback 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.
COPYRIGHT
Copyright (C) 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. http://opencontent.org/openpub/.
[FIXME: source] 05/30/2012 GLBEGINTRANSFORMFEED(3G)