One of Sega’s most mysterious products ever, the canceled Sega VR headset, finally emerged in a “playable” form on Friday thanks to a team of game history preservationists. It’s a tale of a discovered ROM, a search for its source code, and efforts to not only rebuild the game but also adapt existing Genesis and Mega Drive emulators to translate virtual reality calls from today’s PC headsets.

The story, as posted at the Video Game History Foundation’s site, begins with a ROM discovery by Dylan Mansfield at Gaming Alexandria. The game in question, Nuclear Rush, was one of four games announced for Sega VR, a headset system designed to plug into standard Genesis and Mega Drive consoles.

Not quite 72Hz…

Gamers from that era likely heard about Sega VR, as the game publisher’s PR push included plenty of mentions in gaming magazines, a public reveal at 1993’s Summer CES, and even a segment on ABC’s Nightline. But the ambitious device, slated to launch at a mere $199, was quietly canceled, and former Sega President Tom Kalinske eventually confirmed why: researchers found the device made a huge percentage of testers sick with headaches and dizziness.

Today’s discovery explains in part where those sickness symptoms likely stemmed from. By breaking down and understanding the way Sega VR games communicated with a Genesis, and therefore a Sega VR headset, VGHF digital conservation head Rich Whitehouse discovered the headset’s severe limitations: a mere 15Hz refresh for its stereoscopic images, as opposed to the 72Hz minimum for Oculus Quest (let alone the 90Hz standard established by companies like HTC and Valve). Additionally, Sega VR only translated pitch and yaw movement for users’ heads, not roll—and that’s on top of the system already being limited as a three-degrees-of-freedom (3DOF) system, requiring that users stay seated.

How did Whitehouse find out so much about Sega VR’s functionality this many years after the add-on vanished? As it turns out, Mansfield’s day-to-day search for game history errata includes requests to various ’90s developers for whatever old prototypes or code they might have tucked away in a drawer. In the case of Kenneth Hurley, who worked on Nuclear Rush as part of Futurescape Productions, he went one higher and sent Mansfield a CD-ROM dated August 6, 1994—which miraculously hadn’t succumbed to bit rot.

Whitehouse stepped in at this point to figure out how to compile the leftover nearly complete code (dubbed “final” but not “retail final”), which required a mix of C and assembly. Among Whitehouse’s discoveries: the code as written only worked on certain Genesis and Mega Drive hardware revisions, based on how it handles horizontal and vertical scrolling of sprites and assets, which required a minor fix. Also, metadata in the code hinted to a Winter CES 1994 showing for Sega VR that never came to pass.

Could have used an SVP

Though the discovered CD-ROM was missing key Sega VR files (which Whitehouse says would have been named VR.DOC and VR.TXT), Whitehouse was still able to work out how the system would have worked with 16-bit consoles. Sega VR IO would have revolved around the console’s second controller port—though Whitehouse’s explanation doesn’t clarify whether the console’s video-out port would have been redirected to the Sega VR headset or how that would have worked. Additionally, the Sega VR headset would have been fed two 30Hz images, which Nuclear Rush would have then divided further with its 15fps refresh.

While figuring out how to make Nuclear Rush work as a VR experience in 2020, Whitehouse talked to the game’s original lead programmer, Kevin McGrath, who confirmed that his team did a lot of work on Sega VR without actually having a headset to test on—and they invented a test that had the game’s video output flicker between two computer monitors to see how it might do the same with two headset images. Another Sega VR-era game programmer, Alex Smith, confirmed that the team working on Outlaw Racing never even went hands-on with a headset prototype before its project was canned.

The rest of Whitehouse’s work revolved around building OpenVR support into a working Genesis emulator, which included, among other things, doing serious guesswork about how Sega VR’s panels were positioned and shaped, then fixing 1994-era quirks to run more efficiently on modern computers (in part to reduce potential motion sickness from a Genesis-era game locked at 15fps). The resulting emulator and a pair of compiled Nuclear Rush ROMs are available for download and testing from the VGHF article.

Ars Technica has tested this combination of emulator and ROM on a Windows 10 PC running an HP Reverb G2 headset, and I can confirm that the game plays about as well as you might expect: it’s a rudimentary 3D tank game, as if Atari’s arcade classic Battlezone had been rebuilt with Genesis-era sprites and palettes, but it’s all sprite-field trickery, not the rudimentary polygonal stuff of early ’90s fare like Star Fox or Virtua Fighter. (Sega VR games clearly weren’t being bulked up with extra on-cartridge chips like Sega’s SVP, used in the Genesis version of Virtua Racing.)

The resulting restored game isn’t a revolutionary gameplay experience by any stretch. Still, the combined efforts of everyone listed above brought life back to a game whose original version would likely have made you sick. Thankfully, modern hardware (and its enterprising users) can revive canceled games in ways that won’t make game history aficionados toss their cookies, and that’s a testament to the modern game-preservation movement as a whole.

Check out the whole intriguing story, complete with a ridiculous amount of technical information, at the Video Game History Foundation.

https://arstechnica.com/?p=1724674