   <span class="comment">%------------------------------------------------------------------</span>
        <span class="keyword">function</span> createInteractPP(this,drv,p1,p2,addVL)
            <span class="comment">% Compute separation between particles surfaces</span>
            <span class="comment">% PS: This is exclusive for round particles to avoid calling the</span>
            <span class="comment">%     base kinematic object (a bit slower).</span>
            <span class="comment">%     For oth