Forza Motorsport's highly-regarded (and dangerously addictive!) "suggested line" driving aid was one of our innovations.

A game like Forza, which heavily (and successfully we'd like to think) emphasises the simulation aspect of the driving and racing experience, can be difficult for a new player to come to terms with. To counter this, and boost the accessibility of the game, the "suggested line" driving aid was conceived.

The idea of rendering a line on the track for the player to follow is of course a rather obvious one. What makes the Forza implementation of this device so effective is the way that speed information, and thereby acceleration and braking hints, are progressively displayed and dynamically encoded in the line in real-time.

The principle is nevertheless straightforward. The combination of the topology of the track ahead, the geometry of the racing line upon it, and the properties of the car place a limit on the maximum speed the player can hope to sustain at any given point (i.e. go any faster, and a loss of grip and thus control is likely). If the player is currently going faster than the maximum speed at that given point ahead, the line is variably shaded in red in that location. If the player is going slower, it is shaded in green. By this mechanism, the player is given a clear and progressive indication of the requirement to brake, or accelerate, in multiple places ahead. Furthermore, this information is updated frame-by-frame, and so immediately reacts to any changes in speed the player may make.

Although the principle is straightforward, the implementation nevertheless is highly dependent on the accuracy of the "maximum" speed prediction, based on car, track and racing line properties. The novel solution to this problem that was derived for the Drivatar system turns out to be very accurate. While its certainly not perfect (it is an approximation after all), it is more than sufficiently reliable to make the suggested line system work extremely effectively.