void clear() {
		setRefreshing(true); // XIE: move up for refreshing in the first time
		if (modelManager.getFrame() == null)
			return;
		setBooleanProperty("slabEnabled", false);
		fileManager.clear();
		repaintManager.clear();
		transformManager.clear();
		pickingManager.clear();
		selectionManager.clear();
		clearAllMeasurements();
		modelManager.clear();
		statusManager.clear();
		stateManager.clear(global);
		refresh(0, "Viewer:clear()");
		// g3d.destroy();
		System.gc();
	}