GLBEGINTRANSFORMFEED(3G)

    .SH "NAME" glBeginTransformFeedback - start transform feedback operation
    .SH "C SPECIFICATION"

            .HP u void glBeginTransformFeedback(GLenum primitiveMode);

            .HP u void glEndTransformFeedback(void);

    .SH "PARAMETERS FOR GLBEGINTRANSFORMFEEDBACK"

        .PP primitiveMode

                    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 glBeginTransformFeedback until a subsequent call to glEndTransformFeedback. Transform feedback commands must be paired. An implicit glResumeTransformFeedback() is performed by glEndTransformFeedback if the transform feedback is paused. Transform feedback is restricted to non-indexed GL_POINTS, GL_LINES, and GL_TRIANGLES.
            .PP If no geometry shader is present, while transform feedback is active the mode parameter to glDrawArrays() and other drawing commands must match those specified in the following table:
            .TS allbox tab(:); lB lB. T{
                            Transform Feedback primitiveMode
    T}:T{
                            Allowed Render Primitive modes
    T} l l l l l l. T{ GL_POINTS T}:T{ GL_POINTS T} T{ GL_LINES T}:T{ GL_LINES,
                            GL_LINE_LOOP,
                            GL_LINE_STRIP,
                            GL_LINES_ADJACENCY,
                            GL_LINE_STRIP_ADJACENCY T} T{ GL_TRIANGLES T}:T{ GL_TRIANGLES,
                            GL_TRIANGLE_STRIP,
                            GL_TRIANGLE_FAN,
                            GL_TRIANGLES_ADJACENCY,
                            GL_TRIANGLE_STRIP_ADJACENCY T}

            .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{
                            Transform Feedback primitiveMode
    T}:T{
                            Allowed Geometry Shader Output Primitive Type
    T} l l l l l l. T{ GL_POINTS T}:T{ points T} T{ GL_LINES T}:T{ line_strip T} T{ GL_TRIANGLES T}:T{ triangle_strip T}

        .SH "NOTES"
            .PP 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 ES version is 3.2 or greater.

        .SH "ERRORS"
            .PP GL_INVALID_OPERATION is generated if glBeginTransformFeedback is executed while transform feedback is active.
            .PP GL_INVALID_ENUM is generated by glBeginTransformFeedback if primitiveMode is not one of GL_POINTS, GL_LINES, or GL_TRIANGLES.
            .PP GL_INVALID_OPERATION is generated if glEndTransformFeedback is executed while transform feedback is not active.
            .PP GL_INVALID_OPERATION is generated by glDrawArrays() and other drawing commands if transform feedback is active and mode is not compatible with primitiveMode as described above.
            .PP GL_INVALID_OPERATION is generated by glBeginTransformFeedback if any binding point used in transform feedback mode does not have a buffer object bound. In interleaved mode, only the first buffer object binding point is ever written to.
            .PP GL_INVALID_OPERATION is generated by glBeginTransformFeedback 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 "API VERSION SUPPORT"

            .TS allbox tab(:); l l l l l l l l l l. T{ glBeginTransformFeedback T}:T{ T}:T{ T}:T{ T}:T{ T} T{ glEndTransformFeedback T}:T{ T}:T{ T}:T{ T}:T{ T}

        .SH "SEE ALSO"
            .PP glPauseTransformFeedback(), glResumeTransformFeedback()

        .SH "COPYRIGHT"
            .PP Copyright © 2010-2015 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/.

COPYRIGHT
Copyright © 2010-2015 Khronos Group