Someone who can't see 3D images uses an Oculus Rift for the first time.

   Last night, at Oxford Hackspace, I had my first try at an Oculus Rift VR headset. It was running one of the Rift demos, an office desk with a lamp and a playing card castle on it. Nothing unusual there, you might say. I'm guessing first Oculus experiences aren't much to write home about these days.
    I am maybe not in Oculus's sights though as a customer, because as I've written here before I was born with a strabismus. I have perfect vision in both eyes, but my left eye looks somewhere around twenty degrees to the left and I can switch my main vision from eye to eye. This means I can see over my left shoulder, keep an eye on the mirror without taking an eye off the road while driving a right hand drive car, and move my left eye independently of my right as a party trick.
    It also means I can't see in 3D in the same way as someone born with both eyes on the same heading. In the few months following my birth when my brain was configuring itself for the world around it, I never acquired the capacity for seeing objects as three-dimensional by combining images from left and right eyes because my eyes didn't deliver images close enough to each other. This doesn't mean I live in a flat two-dimensional world, it simply means I don't process 3D information in the same way as other people. To use an analogy of a modern computer system, I do my 3D processing in software rather than hardware. My brain developed to interpolate 3-dimensional space from a single 2-dimensional image and sometimes by the effect of my movement rather than by comparing two such images from different angles. I live in a 3D world, but sometimes - as for instance when trying to be a batsman in a school cricket team - things happen a little too fast for my 3D processing to follow.
    All of this means that 3D effects designed for people without a strabismus - stereograms, autostereograms, and 3D movies - don't work for me. I will never be able to see an autostereogram, and a 3D movie is for me a 2D movie in which I disregard what's being sent to my left eye. Fine by me, I'm happier to pay less for a 2D showing anyway.
    So I didn't expect much from the Oculus. And yes, once looking into it the feeling was of having a couple of normal 2D screens in front of me. Not too different from my day-to-day workstation, except with full-field vision rather than a pair of LCD monitors.
    The sight of assorted geeks queuing up to flail blindly about a crowded hackspace wearing a headset is mildly amusing. In my case trying to keep my movements to a minimum I started to look around. Looking down, the desk and the lamp were just a 2D picture of a desk surface and a lamp. Switch from eye to eye, nothing changes.
    It was a mild surprise when I moved my head to the left and the card castle came into view. It was a picture of a card castle on a monitor, then suddenly it was a 3D card castle. Swing back to the lamp, and it's a picture of a lamp. Back to the card castle, and it's a 3D object. I was only using my right eye, but I could see inside it as I knelt down.
   So I had one 3D object in otherwise 2D space. Not really Better Than Life, but far more than I expected. What's happening here? In the real world, I interpolate 3D even when I'm not moving because I know something about the environment. I know a teapot in front of me is a 3D object because I have a huge amount of real-world lighting and other visual information. I can reach out and touch it. That knowledge means that when I reach out to take hold of it I know not only roughly where it is, but what size it is so I can grasp its handle with a good expectation of the dimensions my hand will have to close over. If I move around an object the amount of information I have about it increases, and so does my ability to see it in 3D.
    I think that there is an information threshold for me to see something in 3D. A 2D image on a screen or a page does not have enough information from its lighting or how its aspect changes for me to see it as containing 3D objects. I think the lamp and the desk did not pass this information threshold while the card castle did. It had enough complexity for it to provide my brain with the information it needed to cross the threshold as my motion caused the Oculus image to change.
    This opens up the interesting prospect of people with a lifelong strabismus having an ability not shared with most others: that of seeing a 3D image from a single 2D source when that source is coupled with motion sensing. It would be extremely interesting to see if a 3D-rendered-as-2D FPS game could become 3D-immersive for me if it were displayed on an Oculus with its motion sensor controlling in-game movement.
    I am guessing I only have this ability because my strabismus is life-long. I gained it because my brain developed with it, I am therefore guessing someone who grew up with stereoscopic vision but later lost an eye or gained a strabismus through injury would not see a 2D image as 3D in an Oculus headset. I'd be interested to hear whether or not that was the case.
    Some people have a big problem with strabismuses. Parents subject their children to surgery without their consent to have them "corrected". Says more about their insecurities and the desire for "perfect" offspring than it does about the effect of a strabismus. Mine has mostly never been an issue, sometimes it's unnerved people and I'll never play cricket or baseball. I would never subject a child of mine to unnecessary cosmetic procedures, to me a strabismus is just part of who you are. Yesterday's experience added a new angle on my strabismus and for that I'm happy. I can add seeing 2D images in 3D to seeing over my shoulder in the meagre list of super-powers it's given me.