public void showVelocity(int index, boolean on) {
		if (index < 0 || index >= MolecularModel.SIZE)
			return;
		if (on) {
			Atom at = model.getAtom(index);
			viewer.setAtomVelocities(index, at.getVx(), at.getVy(), at.getVz());
		}
		velocityBitSet.set(index, on);
		repaint();
	}