public void loadWorldDescriptor(String fname) {
		WDLoader loader = new JAXBWDLoader(fname);
		WorldDescriptor descr = loader.load();
		if (descr != null) {
			long dly = 100;
			if (sim != null) {
				dly = sim.getDelay();
				sim.stopSimulation();
			}
			sim = new Simulation(descr, dly);
		} else
			ui.error("Could not load world descriptor file.");
	}