Eagle Flight is a VR game about becoming a bird, soaring high above the streets of an unpopulated Paris, swooping through the tiniest of alcoves and diving through the empty buildings, guiding yourself through the air by simply aiming your gaze.

Ubisoft Montreal came up with the concept while playing around with the strengths and limitations of VR, testing how to best explore and interact with virtual spaces. While seeking a balance between comfort and exhilaration, they stumbled across their unique control scheme.

The controls are so simple and intuitive that explaining them almost seems redundant. To go left, tilt your head left. To go right, tilt your head right. To climb or dive, tilt your head up or down. The head mounted display tracks the subtle movements of your head, and the game translates them into minor course corrections in the bird's flight path.

"There was something very natural, almost universal in this way of moving in the world, bringing back those dreams where you fly that are always too fleeting," says Charles Huteau, creative director on Eagle Flight. "The prototype delivered that dream. We knew that we had something unique on our hands."

Hitting upon a startlingly direct control scheme

Huteau said that Eagle Flight began with a very small team led by game director Olivier Palmieri that was simply doing R&D on virtual reality. "Their goal was to comprehend this new piece of technology and its limitations in order to be ready when the time came to make games with it," says Huteau.

Ubisoft Montreal had been testing several different control styles and concepts to see which ones would give the player a great gameplay experience without making them feel ill or disoriented. "They created several prototypes, exploring different ways of navigating in space and interacting with a virtual world," he says. "They started playtesting internally to see how people would respond, what would trigger the most exciting sensation while staying the most comfortable." 

In their testing, a single concept stood out above all the rest. "One of those prototypes came out very unique, with feedback scores off the charts. It was flying controls, and surprisingly, it wasn’t a plane or spaceship-type of controls," says Huteau. "Actually, quite the opposite." 

To Huteau, the distinction is very important. "There was zero inertia between the commands the player was giving and the response from the game," he says. "They weren’t piloting something. They weren’t 'inside' a vehicle. They were literally flying, and reactions were immediately super positive."

The key to the success of the game was cutting out the middleman. Not just the middleman of a pilot within the game world, but the middleman of a gamepad used to input commands. "There’s something very simple and intuitive about those controls," says Huteau. "When you try Eagle Flight for the first time, you quickly notice that using your head to 'point' where you want to go feels super natural. Way more logical for your body than sending an order to your thumbs to push sticks in 2D directions."

The same technology that allows a head mounted display to gauge your head movements so that your field of view shifts in the virtual world makes this sort of subtle and immediate flight control possible. "VR headset tracking is so precise that each degree of orientation is taken into account on three axes." says Huteau.

"That means that, after just a few minutes playing our game, you feel like an expert pilot. You’re able to fly through the city and come really close to buildings or the ground with total control, and you will succeed to pass through obstacles that seem impossibly tight. People watching the screen while you play are often scared for you because, from their perspective, you’re flying through the eye of a needle. But in the headset it’s very different - you feel totally in control and the tracking offers you a degree of accuracy that no game pad or joystick can compete with."

Limiting field of view to boost comfort

After playtesting with over 400 people internally, they began taking the prototype to events like E3 and Gamescom for playtesting. "The data we gathered helped us a lot in refining every detail, from the angle for your tilt command, to the maximum speed when you dive and the curve of acceleration." says Huteau. "All those parameters were very sensitive, and if we weren’t cautious with those, the game was broken and nobody could play safely – even our team."

They discovered a fundamental issue with their gaze-controlled game--one that would force them to dynamically change the gaze.

"Very early on, we noticed that players who were sensitive to motion sickness had almost no problem flying high in the sky, but as soon as they were diving in the city and flying low, comfort was broken," says Huteau.

The developers discovered that fast-moving objects in your peripheral view triggered nausea very quickly. “In real life, for most people, your brain creates a tunnel vision to help you concentrate on the center of your view,”  says Huteau. “In VR, we needed to help it a little."

They created “dynamic blinders” that track your orientation and your position in space. “When you fly too close to an object, we start closing that side of the screen for you to mimic tunnel vision. The beauty of this  is that, when you play, you won’t notice it much," says Huteau. "It is one of the features that our team is really proud of because it allowed people who were very sensitive to suddenly enjoy a VR experience without any issues."

This visual effect would be key in a game about controlling motion with head movement and the player's eyes, as it would keep them from getting sick at the high speeds the game offered them. If the developers were to help players achieve that sensation of real flight, they would need to keep players from feeling sick as they rushed through city streets and over rooftops.

The fact that designers have to grapple with issues like this might make VR seem daunting. But Huteau prefers to see if as part of the reason that so unique.

“The immersion into the virtual world is so intense that it goes both ways: when you design your experience well, the sensations are outstanding. When you’re not careful, it’s a disaster and you reach that point where nobody can play anymore. You can’t ignore the issue, and have to fix it if you want to go further. That’s a super cool design constraint, honestly."