ge assigned to each vertex captured in transform feedback mode
            where the value of the variable will be stored.  Such offsets are
            specified via the <code class="code">xfb_offset</code> layout qualifier or assigned according to
            the variables position in the list of strings passed to
            <a class="citerefentry" href="glTransformFeedbackVaryings"><span class="citerefentry"><span class="refentrytitle">glTransformFeedbackVaryings</span></span></a>.  Offsets are expresse