Provided by: opengl-4-man-doc_1.0~svn22917-1_all bug

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:

       ┌──────────────────────────────────┬─────────────────────────────────────────────────┐
       │                                  │                                                 │
       │                        TransformAllowed                 │
       │Feedback primitiveModeRender Primitive modes                          │
       │                                  │                                                 │
       ├──────────────────────────────────┼─────────────────────────────────────────────────┤
       │GL_POINTSGL_POINTS                                       │
       ├──────────────────────────────────┼─────────────────────────────────────────────────┤
       │GL_LINESGL_LINES, GL_LINE_LOOP,                         │
       │                                  │ GL_LINE_STRIP,                                  │
       │                                  │                         GL_LINES_ADJACENCY,     │
       │                                  │ GL_LINE_STRIP_ADJACENCY                         │
       ├──────────────────────────────────┼─────────────────────────────────────────────────┤
       │GL_TRIANGLESGL_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:

       ┌──────────────────────────────────┬──────────────────────────────────┐
       │                                  │                                  │
       │                        TransformAllowed  │
       │Feedback primitiveModeGeometry Shader Output Primitive │
       │                                  │ Type                             │
       │                                  │                                  │
       ├──────────────────────────────────┼──────────────────────────────────┤
       │GL_POINTSpoints                           │
       ├──────────────────────────────────┼──────────────────────────────────┤
       │GL_LINESline_strip                       │
       ├──────────────────────────────────┼──────────────────────────────────┤
       │GL_TRIANGLEStriangle_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 © 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/.

AUTHORS

       opengl.org