boolean hbondsAreVisible(int modelIndex) {
		if (frame == null)
			return false;
		int bondCount = getBondCount();
		Bond[] bonds = frame.bonds;
		for (int i = bondCount; --i >= 0;)
			if (modelIndex < 0 || modelIndex == bonds[i].atom1.modelIndex)
				if (bonds[i].isHydrogen() && bonds[i].mad > 0)
					return true;
		return false;
	}