This is a screen capture at Cal Maritime of a Transas simulation of a Damen 2411 Z-Drive tug escorting a tanker. The tug controls are in the lower right and the red oval indicates the towline force generated by the tug. Ship's speed is about 6 knots.
The pilot orders the tug to "Indirect My Port" because he/she wants to assist the vessel in turning to starboard or the ship's rudder might have failed to port.
The red oval indicates the towline force, the green oval is the tugs speed and course over ground. The force is relatively low because the order is "indirect" not "power indirect".
The tug controls indicate direction and power order to the z-drive units.
The second half of the video illustrates the vectors developed in the towline. The white arrow is the braking vector, the yellow line is the towline vector and the red line is the steering vector.