// maintain a set of items that should be interpolated linearly
// this isn't absolutely necessary, but makes the animations nicer
// the PolarLocationAnimator should read this set and act accordingly
vis.addFocusGroup(Constants.LINEAR, new DefaultTupleSet());
vis.getGroup(Visualization.FOCUS_ITEMS).addTupleSetListener(
new TupleSetListener() {
public void tupleSetChanged(TupleSet t,
Tuple[] add,
Tuple[] rem) {
TupleSet linearInterp = vis.getGroup(Constants.LINEAR);
if (add.length < 1)