Mark Rober, who is best known for his YouTube videos of spectacular science stunts, has been quietly working as an engineer for Apple’s secretive special projects group, Variety has learned. Rober’s work for Apple includes contributions to the company’s virtual reality projects, with a focus on using VR as on-board entertainment for self-driving cars.

An Apple spokesperson declined to comment when contacted for this story. Rober didn’t immediately respond to a requests for comment.

Rober, who has close to 3.4 million YouTube followers and has been an occasional guest on “The Tonight Show With Jimmy Fallon,” changed jobs in the summer of 2015, according to his Linkedin profile. The profile currently states that he has been working as a product design engineer at an unnamed company ever since.

In a Reddit AmA, Rober told fans a year ago that he was working at “a large tech company in the Bay Area.” He declined to name the company, saying that he was asked not to, but added: “I work on the team formulating products that haven’t been released.”

Some patent applications filed by Apple this spring give us an idea of what Rober has been working on: In March, Apple filed a patent application for an “immersive virtual display” as well as one for an “augmented virtual display.” Both describe VR systems that could be used by passengers of self-driving cars, who ostensibly weren’t needed to observe traffic anymore.

Courtesy of Apple

From Apple’s patent application for an “augmented virtual display.”

Apple has been vocal about its interest in augmented reality (AR), and released a framework for phone-based AR dubbed ARKit last year. The company has been much quieter on virtual reality, as well as plans to bring either of those technologies to future headsets. Cnet reported in April that Apple was working on a headset that would combine both AR and VR, with a goal of shipping the device in 2020.

Apple’s AR/VR efforts and its work on autonomous cars have long been closely related. Case in point: Munich-based AR startup Metaio, which Apple acquired in 2015, had been working with several car manufacturers, including Audi, BMW and Ferrari. However, Apple reportedly scaled back its autonomous vehicle efforts last year, and more recently focused on partnerships with vehicle makers to build on-campus transportation for its own employees.

Courtesy of Apple

From Apple’s patent application for an “augmented virtual display.”

Interestingly, Apple has apparently been thinking about ways to integrate real-world data from vehicles into the VR experience. From the patent application for an augmented virtual display:

“Embodiments of the VR system may provide enhanced immersive virtual experiences to passengers in moving vehicles that are not achievable in conventional stationary VR systems. Integrating the VR system with a vehicle in motion provides opportunities for enhancing virtual experiences that are not available while sitting in a room using a stationary simulator or wearing a (VR headset). For example, accelerations and motions in a virtual experience can be matched to or enhanced by accelerations and motions of the vehicle, and thus do not have to be simulated using gravity vectors as in a stationary simulator.”

Courtesy of Apple

From Apple’s patent application for an “augmented virtual display.”

The patent application also mentions the possibility of incorporating social VR as well as virtual avatars into a in-vehicle experience: “For example, a virtual representation of an author or talk show host may appear to be sitting in the seat next to the passenger; the virtual author may be reading one of their books to the passenger, or the virtual talk show host may be hosting their show from the seat next to the passenger, with their voices provided through the audio system. As another example, the passenger may experience riding on a flatbed truck with a band playing a gig on the flatbed, with the band’s music provide (sic) through the audio system.”

And while Rober’s Apple patent applications are primarily focusing on VR for autonomous cars, a lot of the technology described could also be used for VR in other contexts. For instance, the “augmented virtual display” patent application describes ways to combine virtual TV screens, e-books and other content in VR while at the same time still providing real-world visual cues — something that could be essential to any attempt to build a headset that combines AR and VR, whether it is used in a moving vehicle or not.