private void paintForce(Graphics2D g) {
		for (Node node : model.getNodes()) {
			g.setColor(Color.BLUE);
			g.drawLine((int)(margin_x+node.pos_x*min_size), 
			           (int)(margin_y+node.pos_y*min_size), 
			           (int)(margin_x+(node.pos_x+node.for_x)*min_size), 
			           (int)(margin_y+(node.pos_y+node.for_y)*min_size));
		}
	}