As part of Devcom 2017, Joey Fladderak, a programmer at Sticky Studios, gave a talk about the lessons he learned from porting mobile games to mobile VR. Sticky Studios is the developer behind games such as Suicide Squad: Special Ops, which Fladderak used as his main case study.
Fladderak said, "We felt that this would be very well suited for a VR game", even though it had been designed without any VR functionality in mind. Despite this, the final product ended up quite close to the original.
The first step was to adapt the initial game design to VR. This required the team to rethink the scope of the game to accommodate shorter play sessions, as well as rethinking movement in the game.
While the original mobile release had free movement handled with a joystick, this didn't suit a Gear VR launch due to the potential for motion sickness. Allowing players to teleport between nodes also didn't work for the game because of its fast-paced nature.
In the end, the studio settled for a static viewpoint, despite the fact they felt that exploration was a key pillar of the experience. To combat this, they picked out the most interesting viewpoints in each room of the game, and swapped characters each time a new level started to bring variety to the game.
Suicide Squad also faced performance issues preventing it from hitting a suitable frame rate, leading to an interesting solution in which backgrounds were changed from fully-3D objects to blank cubes with 2D images painted on them, while still appearing 3D.
As for changing the UI for mobile VR, Fladderak recommended that developers, "Don't start too early" when designing the interface – it's difficult to tell what may and may not work until you actually have the game in working order.