Sony originally designed the PlayStation 4's DualShock 4 controller with virtual reality in mind, and that's the reason why it has a lightbar. Speaking with TechRadar, Sony senior designer Jed Ashforth said, "The tracking light… it was our department that said we need that on," he said. "It was for tracking for VR."
The PS4 was released six months ago, and Sony began talking about the system and showing off the controller even before that. This meant Ashforth and the rest of his team had to keep quiet about the real purpose for the DualShock 4's lightbar, even as fans began to wonder.
"When all these things were coming out six months ago and everyone was going 'it's reflecting in my TV,' we were going 'oh no' because we couldn't tell anyone what it was for," he said.
Sony finally announced its PS4 virtual reality initiative, Project Morpheus, during the Game Developers Conference in March.
The DualShock 4's lightbar can be dimmed, but you can't turn it off, at least not yet. Right now, the lightbar's functionality is fairly limited. It works in conjunction with the PlayStation Camera as a tracking beacon. When multiple gamers are playing together, the lightbar will designate each player a color (blue, red, green, pink) depending on the order in which they press the PlayStation button.
The PS4 launched in November 2013 and has sold over 7 million consoles to date.