ate,
    values provided via the generic vertex attribute
    <em class="parameter"><code>index</code></em> will modify the value of the
    user-defined attribute variable specified by
    <em class="parameter"><code>name</code></em>.</p>
        <p>If <em class="parameter"><code>name</code></em> refers to a matrix
    attribute variable, <em class="parameter"><code>index</code></em> refers to the
    first column of the matrix. Other matrix columns are then
    automatically bound to locations <em class="