Turn 10 gets technical with Ars, explaining some of the nuts and bolts inside Forza Motorsport.

Microsoft made a big show of officially announcing Forza Motorsport 6 at its pre-E3 press conference this morning, but we here at Ars got our hands on the game days ago. Last week, Ars traveled to Redmond, Washington, to visit Creative Director Dan Greenawalt and his team at Turn 10 for an exclusive, world-first look under the hood of the latest iteration of this franchise. What we saw was nothing less than one would expect from a team with depth and breadth of experience, one that's been in place since the franchise premiered on the original Xbox in 2005. What we saw made September 15—the game's US release date—seem an awful long way away (other countries will have to wait even longer—Japan gets it on the 17th, with the rest of the world on the 18th).

We knew a bit about the game before the trip. Thanks to a screw up at Microsoft Japan, we learned that FM6 will feature 450 cars, 26 tracks (including some new ones like Daytona and Rio), as well as night racing and wet weather. Turn 10 Studios has also bumped up the car count in each race; now grids are 24-deep, with no change to their core mantra of "1080p 60fps."

With Forza Motorsport 5, the team at Turn 10 was still struggling to learn how to develop for new console hardware and rushing to finish development in time for launch. As such, Forza Motorsport 6 makes much fuller use of the Xbox One's power, something studio head Alan Hartman attributed to a stable codebase for the rendering and physics engines. The new version also benefitted from the work of UK-based Playground Games, which brought us last year's open-world Forza Horizon 2. That game featured dynamic day-to-night transitions and weather, but did so at the cost of frame rate. Those compromises are now gone, the product of "two great studios working with the same codebase," Hartman told Ars.

Simulating the wet and the dark

The resolution and frame rate weren't the only non-negotiable features. With FM6, Greenawalt and his team say they want to accurately deliver the feeling of driving on wet pavement. That's something the Turn 10 team knows quite a lot about, given the weather in the Seattle area. As Alan Hartman put it: "Dan hates it when I say this, but we live in Seattle, we know what driving in rain and hydroplaning is like. So when we started getting it right and people would say, 'Yep, this is it,' it's not just making the entire track 15 percent more slippery. It's about picking your line, worrying about puddles, worrying, 'Oh shit I just dragged the left side of the car through a puddle.' When that stuff started coming into the build, it started clicking with people."

A brief primer on Physically Based Materials According to Chris Tector, Turn 10's software architect, PBMs solved the problem of a game that was getting too large for developers to hand-tune the look of each different material used in each car and track. "For example, in the past we'd have issues with a white car that looks great on one track but terrible on another, because some of the weird multipliers we'd have in place wouldn't be doing the right thing [on the second track]," he said. This happened across other colors, as well. "Black cars looked great, red cars looked pretty good, yellow cars would be weird and blow out at certain points, and then white was the hardest," he said. According to Chris Tector, Turn 10's software architect, PBMs solved the problem of a game that was getting too large for developers to hand-tune the look of each different material used in each car and track. "For example, in the past we'd have issues with a white car that looks great on one track but terrible on another, because some of the weird multipliers we'd have in place wouldn't be doing the right thing [on the second track]," he said. This happened across other colors, as well. "Black cars looked great, red cars looked pretty good, yellow cars would be weird and blow out at certain points, and then white was the hardest," he said. "With the move to PBM (in FM5), it really changed that story for us. It's about how many properties you want to model," he said. Cars and tracks are modeled with a layered approach. "You know what the different layers of paint and coating do to refraction—a diffuse base layer, a more transparent layer with metal flake, a clear coat—each one has different properties that affect the light," he said. "We want to attenuate the light as it refracts, so when it hits the flake it's a different brightness than when it was coming in the surface or bouncing back out," he told Ars.

This level of simulation required adding a new layer of complexity to the game's engine. When FM5 was written for the Xbox One, Turn 10 adopted a new way of modeling. Out was the old reliance on mere polygons and textures, in came physically based materials, or PBMs. "We're talking about the physics as well as rendering," Greenawalt said. "We learn things through the rendering side that affect physics and vice versa. For example, if we learn why a wet rumble strip is shiny visually, it tells us something about the physics," he said.

This kind of simulation doesn't only help with the game's realism, but also streamlines the development of a game that was getting too unwieldy to tune by hand, Greenawalt said. "Teams have gotten more complex, games have gotten bigger, we've been able to do more," he told Ars. "The role of intuitive custom tuning or brute force doesn't scale. The theme we found over and over again to fix things was physics, and it put it right in our wheel house," he said before noting that the increased reliance on physics was incredibly useful: "It was a real help when we did night and rain because we could apply it." (see sidebar for more on this)

The newest addition to this aspect of FM6 was the porosity of a material, which affects how water sticks or runs off a surface. Bill Giese, creative director for FM6, described the tension of racing in wet conditions that the game is trying so hard to capture: "The pucker moment." To achieve that moment, Turn 10 visited race tracks, capturing surface types and measuring details down to the depths of puddles and the way water accumulates differently across a track. The team calculated porosity for 148 different types of surface with wet and dry values.

Giese uses Sebring as an example, a track with concrete and asphalt sections joined by transitions covered in sealant. "Even that has different properties," he said. "It affects the way it looks but also the way the player experiences it through the game, in a unified way. So the way the rain drops streak across the screen or the way driving through a puddle pulls you sideways," he said.

Disappointingly, this focus on wet driving doesn't include the addition of dynamic weather. Consequently, the race track won't change over the course of a race; no dry lines appearing on the track, no growing or shrinking rivers across different parts of the course.

The aim of adding night racing was also to evoke different emotional responses. Night racing under the stadium lights of Yas Marina or Daytona should give a player a sense of the grandeur of the events, Giese said. He contrasted that with Le Mans, where "it's just you and your headlights; 'I've got tunnel vision. I hope I can see the car in front's brake lights so I can see where the brake markers are." Racing in such limited visibility, you should be fearful of what happens when you see and hear a faster car coming up behind you, he said. And no, extra lights will not be available as upgrades to alleviate these fears.

Anyone who's ever raced at night will be familiar with these sensations. We didn't play the game enough to see if it also replicates that other aspect of night racing on a dark track, where inadequate lighting couples with track elevation to hide corner apices and clipping points. Racing in these conditions requires a sense of rhythm and a general trust that the course layout remains the same as it was during the day.

Nick Wiswell, the game's audio lead, showed us some of the improvements his team had made to FM6. There's a greater attention to detail in background noises, like impact wrenches in the pit lane. The sound of other cars has been made a bit more dynamic, as well; if you park and wait in one spot, you'll be able to hear the sound of the other 23 cars rise and fall as they get closer or farther away. The sound of rain hitting the roof of your car will vary based on whether that roof is metal, or carbon fiber, or fabric, and driving through puddles gives you sound cues to add to the haptic feedback.

Listing image by Turn 10