How GT Sport Uses Artificial Intelligence to Calculate Penalties & BoP

Gran Turismo Sport 59 November 29, 2018 by

Despite all the action going on around us at Monaco, GTPlanet was able to sit down with Gran Turismo series creator Kazunori Yamauchi. We had a few questions derived from queries on the our forums, which you can read about more in future articles.

Viewers of the Manufacturer Series final will doubtless have spotted the unexpected result. Despite being strong pre-race favorites, the Nissan team of Igor Fraga (IOF_Racing17), Mikail Hizal (TRL_LIGHTNING) and Ryota Kokubun (akagi_1942mi) soon fell by the wayside.

Before running out of fuel some 300 yards from the finish line, the team had to endure a number of trials. The first was a relatively large penalty on the opening lap, when Kokubun misjudged the NGK Chicane before heading onto the Nordschleife. For what was a relatively minor cut, the six-second slowdown seemed rather harsh.

With the Nissan’s trip to the naughty step still flashing red in our memory, we put the question to Yamauchi of how the game determines the magnitude of any given penalty.

“There’s actually various elements to it,” explains Yamauchi. Firstly the game has to determine that the car has left the track limits. “For example if a car passes through here [off-track], where it needs to go around here [on-track]. When it’s determined that all four wheels cut the inside of that corner, that judgment is binary.”

After that, the penalty system relies on GT Sport‘s AI. Yamauchi continues: “The simplest aspect to it the system is always looking at and comparing how much time gain there was by making that shortcut as compared to the lap time of an AI. Once we know that it did cut, at the next sector it compares the time the AI would have gotten as opposed to the driver, and there you can see how much of a gain there was – two or three seconds or so.”

It’s an interesting approach that could end up punishing faster drivers more; a driver who is particularly adept at a course could see a larger penalty for a small cut simply through being much faster than the AI anyway. “That is a part of the penalty,” says Yamauchi. “It’s not completely exact, but for the most part it’s very fair.”

Polyphony Digital actually uses the AI drivers, in part, to verify the game’s BOP — Balance of Performance — calculations. However, the primary responsibility for this falls on humans.

Just as with the various Sport Mode and FIA race car/track combinations, GT Sport’s BOP comes down to a in-house driver test team.

“We have a few of the top drivers in Gran Turismo throughout the years who’ve joined the company, so they do the final adjustment,” explains Yamauchi. “AI is of course used as a reference, but AIs have certain tracks that they’re good at driving and certain tracks that they’re not good at – or certain corners. So the AI laptimes are used just as a reference.”

“Yesterday in the overall qualifier, the top eight drivers drove an eight-minute track and they were within 1-2 seconds of each other. Revision to the BOP will always be constantly in progress; we did it in the middle of this year.”

Featured GT Sport Photomode image by MrWaflz55.

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