“[Weather is] something which fans have been asking for, for a long time,” says Forza Horizon 2 creative director Ralph Fulton. “[It’s] something which fits our world perfectly; the temperate climate of southern Europe – the changeable weather conditions – it meant we had to look at creating a realistic, physically-modelled atmospheric simulation.”
“That’s about the sky. That’s about the particles in it. That’s about the clouds. That’s about changing dynamic weather conditions: fog, mist, rain, wind. Combining all of those so that not only is the gameplay experience changing as you drive around the world – changing up the handling, changing up the visibility – it’s also changing the beauty of the world you’re seeing.”
Dynamic weather is something that has been some time coming for the Forza series. It’s in Forza Horizon 2 that it will make its long-awaited debut. We’ve already discussed how the team at Playground Games has approached lighting Forza Horizon 2. For instance, we’ve outlined how instead of simply making the sky blue they’ve opted to fill the game’s atmosphere with particles that, when lit by the sun, simulate the real-life optical phenomenon that makes the actual sky appear blue, or red, or any number of shades in between. Perhaps unsurprisingly, Playground Games has attacked weather with the same commitment to realism.
“The way we’ve modelled it is that the atmosphere has a number that will drive up, and that number dictates how much moisture is in the atmosphere,” says art director Ben Penrose. “And as that number starts to climb, you’ll start to see different cloud layers build up.”
Technical director Alan Roberts goes on to explain that the weather in Horizon 2 is fully dynamic.
“We’ve got quite a lot of different systems,” says Roberts. “We’ve got fog and haze. We’ve got rain, clouds, we’ve got wind. We’ve even got rainbows.”
“We can combine all of these in an almost limitless number of ways to give you a load of variety in our weather types throughout the game.”
On screen it’s hard to distinguish the simulated clouds from the ones hanging in the sky outside Playground’s UK studio on what’s otherwise a slightly soggy English morning.
“It’s all down to the kind of things you’d expect in real life,” says Penrose. “So when the atmospheric intensity reaches a certain breaking point you would get rain and, if it carries on, you would get more rain.”
“And that rain will affect all the material on the car and the world in the way you would expect. Cracks in the road will start to fill up with water, or if it’s just light rain the tarmac will just darken slightly. But they’re all nuances we can play with to get a whole range of different scenarios going.”
In a nutshell, the physically-based material system of Forza Motorsport 5 is what gives all the surfaces of the game the extraordinarily realistic finish you may have observed. It’s what makes the surface of a steering wheel entirely distinct from the surface of an alloy wheel. This system has made its way across the Horizon 2, although the team at Playground needed to massage it a little for their needs.
“We’ve modelled wetness into the physically-based material system now,” explains Roberts. “So we’ve researched how wetness affects materials and we’ve plugged that into our physically-based materials system.”
“So we know that when rain hits a surface, we know how it’s going to respond to that rain and therefore how light’s going to affect it. And all of that feeds right through to the simulation so you get effects like beading on the paintwork, and you can see the way rain affects the road surface; it’s all tied together in the physically-based system.”
We pan around the Lamborghini Huracán Penrose and Roberts are using for the purposes of the demonstration. It’s speckled with rain drops and coated in a glossy sheen.
“The raindrops,” begins Penrose, “the way they work [is] they take into account what material they’re interacting with on the car as well, so plastic still looks like plastic, rubber still looks like rubber.”
It’s likely you’ve seen glimpses of the remarkable weather details yourself in the demo playthroughs here on the site, from the way rain assaults car windscreens to the way the blazing sun is reflected from rain-slick tarmac as it burns through the clouds after a brief shower. But Horizon 2’s weather system doesn’t just simulate how things become wet. It also takes into account how things dry once the rain eases.
“The rain simulation takes into account how things get wet and how things get dry,” says Penrose. “It was something that one of the artists picked up on really early on during the researching process and, much to some of the rendering guys’ dismay, it was something we really wanted to get right.”
“So yeah, the roads absolutely get dry in a particular way, and over a particular time scale that you would expect, and it’s the same for the cars as well.”
If it sounds like a lot of effort for something that’ll very likely go unnoticed by a large portion of Forza Horizon 2 players, you might be interested to learn that going unnoticed isn’t necessarily a bad thing.
“We’d take that as a compliment in some ways,” admits Roberts. “If people see it and they don’t notice it, in some ways that’s because it’s done in such a realistic way.”
Penrose elaborates.
“I think that when you’re trying to achieve something that’s as photo real as possible it’s all down to the small details,” he says. “And quite often that is the case; it’s the fine details that maybe people won’t even know they’re there, but if it wasn’t there it would break the illusion.”
“Which is why we go to such lengths to try and get everything as spot-on as possible.”
The team at Playground benefitted from Turn 10’s shift to a physically-based material system but the work required to get weather working in Horizon 2 has still been considerable.
“The great thing is that the guys [at Turn 10] had already made that switch to a physically-based material system, which meant that all of that base information was already there,” explains Roberts. “So it was just a case of going in a making sure the weather effects interacted with those materials in the way you would expect. But just having that information there in the first place was a major benefit.”
“But everything else,” continues Fulton, “the atmospheric simulation, the way we do the sky, the particulates [in the atmosphere], it’s all brand new. Built from the ground up. That’s been a large investment.
For instance, every car built for, or integrated into, Horizon 2 doesn’t just need to be made ready for night racing, it needs to be ready for rain also. That doesn’t just mean making sure the surfaces look right; it also means things like accurately-modelled wipers for every car.
During the E3 demo of Forza Horizon 2 you may have noticed a rainbow over the sea off the coast, arcing from the ocean, high into the clearing sky. The sudden downpour for the brief demo was engineered to give players and observers a taste of Horizon 2’s changing weather, but that rainbow itself wasn’t manually created or positioned there.
“I think the cool thing that I just never understood about this is when that rainbow appears – and you saw it [in the demo] – we didn’t place it there.”
“And I kept saying, can we move that rainbow? And people said, ‘No, because it’s being simulated; it’s about where the sun is in the sky, and the amount of moisture in the atmosphere. It’s just creating a rainbow.”
During the E3 demo of Forza Horizon 2 you may have noticed a rainbow over the sea off the coast, arcing from the ocean, high into the clearing sky. The sudden downpour for the brief demo was engineered to give players and observers a taste of Horizon 2’s changing weather, but that rainbow itself wasn’t manually created or positioned there.
“I think the cool thing that I just never understood about this is when that rainbow appears – and you saw it [in the demo] – we didn’t place it there.”
“And I kept saying, can we move that rainbow? And people said, ‘No, because it’s being simulated; it’s about where the sun is in the sky, and the amount of moisture in the atmosphere. It’s just creating a rainbow.”
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