Oculus Rift is so convincing that I want to throw up. There's the big problem, obviously. It's early July 2013 - that glorious, hopeful period, a few weeks after the death by hellfire of Xbox One's always-on checks, a few months before the trauma of "Resolutiongate" - and I'm playing Undercurrent, a deep sea first-person exploration sim created by students at the University of Teeside.
It's the first Oculus Rift game I've ever played. I don the headset expecting some sort of minor epiphany, a breakthrough "I get it" moment to sell me on why Virtual Reality deserves a second shot after the misfires of the '80s and '90s. Here it is: at one point I glance innocently down through the base of my submersible and see a shark glide between my character's weirdly metallic and fleshless thighs. Shocked, I drive straight into a charming coral formation and flounder there like a concussed jellyfish till my oxygen runs out.
The immediate effect of stereoscopic 3D is to render a world's tiniest, least important details oddly fascinating, even where the art design and assets are relatively primitive or generic. You've seen environments like these before, but for want of a less brain-dead phrase, they've never seemed quite as real. Elsewhere in my tour of Undercurrent's serene ocean floor, I spend a few minutes cooing over a string of bubbles, darting the perspective back and forth as they coruscate past on their journey to the unreachable surface.
Sadly, the experience proves too much for my inner ears, who swiftly identify a mismatch between what my eyes can see and what my body is actually doing. Like rebellious children siding with the more indulgent parent, they express their discontent loudly to my stomach, which then treats my brain to a protracted rebuke. Feeling decidedly green about the gills, I'm obliged to hand the headset back and stagger off in search of a glass of water. On the way back I meet Brendan Iribe, Oculus CEO, who kindly takes a moment to discuss my nausea.
Oculus Rift's motion sickness issue is manageable, but right now - and bear in mind that the technology is in a state of rapid evolution - it doesn't appear to be entirely fixable. Part of the problem could be motion blur, which has apparently been nobbled by the most recent incarnation of the device. But as Iribe explains, there's no easy way to overcome that disconnect between eye and inner ear without either "tricking" the ear as comprehensively as the eye, or softening the visual illusion to the point that it ceases to convince.
"If we take the experience in the same headset, and shrink down the field of view - we letterbox it - you stop getting motion-sick, you stop being disoriented," he says. "As soon as you get that field of view somewhere around the 80-90-100 degrees, your brain suddenly goes 'Oh, I am here, I'm in this virtual place'.
"Then you get an eye to inner ear disconnection, and that's what causes the disorientation. And if you're suddenly running around at 40 miles an hour, or rocket-jumping, or doing something superhuman, but your inner ear thinks you're just sitting in a chair - your inner ear and your eyes will say 'Argh, this doesn't add up, I've taken some kind of drug, what am I on'... Because your inner ear and eyes aren't matching up."