ltiple indices, but you can bind
    multiple user-defined attribute variables to the same
    index.</p>
        <p>Applications are allowed to bind more than one
    user-defined attribute variable to the same generic vertex
    attribute index. This is called <span class="emphasis"><em>aliasing</em></span>,
    and it is allowed only if just one of the aliased attributes is
    active in the executable program, or if no path through the
    shader consumes more than one attribute of a set of attributes
 