MAbrash GDC2013 (16)

In order to keep the visual system from thinking something is wrong, tracking has to be super-accurate.

How accurate?

On the order of a millimeter at 2 meters distance from the sensor.

There is currently no consumer-priced system that comes close to the required tracking accuracy and reliability across a wide enough range of motion.

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So how close is VR tracking right now to what we really want?

Let’s look at what the tracking in the first Rift development kit can and can’t do.

The Rift uses an inertial measurement unit, or IMU, which contains a gyroscope and accelerometer.

IMU-based tracking is inexpensive and lightweight, which is good.

However, it also drifts because there’s no absolute positioning, and it doesn’t support translation – that is, it doesn’t provide accurate reporting of head movement from side to side, up and down, and forward and back, and that’s a significant lack.

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Here we see translation in action. As the head moves from side to side, the virtual view changes accordingly, with nearer objects shifting by greater distances than farther objects. This produces parallax, one of the key depth cues and an important part of making virtual scenes seem real.

In the case of the Rift, translation has little effect on the virtual scene. I say “little” because there is a head and neck model that attempts to reproduce the translation of your head as it rotates, but it has no way to know about translation resulting from any other head movement.

For those of you clever enough to notice that my illustration of translation actually features a Rift, I admit that the translation in these screenshots didn’t come from the head movement – it was simulated by strafing from the keyboard. But that is how translation would look if the Rift did support it.

IMU tracking works for games that don’t require anything but head rotation – FPSes, for example.

But even in FPSes, the lack of translation means you can’t peek around corners or duck down.

In general, the lack of parallax makes virtual images seem less real.

Also, drift means that IMU-based VR can’t stay stable with respect to the real world, and that rules out games like board games that need to stay in one place.

This is definitely a long way from where we really want to be, although bear in mind that this is only the first development kit, and Oculus continues to work on tracking.

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  • WormSlayer

    My brain hurts! Still I’m excited that guys like him are excited :D

  • Patrick Hogenboom

    Thanks a bundle for transcribing the whole thing :)

  • shole

    If you want to view the two videos in the presentation and don’t have ms powerpoint, you can rename the .pptx file to .zip and the files are in there as .wmv under \ppt\media\

    • Michael Abrash

      Shole,

      Thank you very much for posting this!

      –Michael

  • Andrés

    Thanks so much for transcribing this!

  • Andreas Aronsson

    I thought I would not get to read/hear the actual talk in some time :D Very interesting, somewhat alarming, but at the end uplifting and inspiring! Thanks for this! Also, you could if you wanted to rename the .pptx to .zip and extract the videos (media folder) and upload them unlisted to Youtube and embed them on this page :) Just a thought!

  • Andreas Aronsson

    Ah, in the time it took me to read this (left the article half-read over night) shole already pointed this out :x oops.

  • Esse

    “That means that if you fixate on something while you turn your head, your eyes remain fixed with respect to the real world, but move very quickly relative to the display”

    Hum, no. If your eyes are fixed (in the head referential), they are fixed in the display referential. Because the display & the head are fixed one to the other.

    This is over complicating the subject. Only matters the head movement. Not the eyes movements.

    • Ben

      I think that, in this context, “fixate on something” means a visual fixation on an object in the external world rather than having the eyes be “fixed” relative to the head. If the head is turning while you fixate an external object, the eyes must counter-rotate in order to maintain a stable fixation (eg: via the VOR). Since the VR display is attached to your head frame, this means that your eyes are rotating relative to the display, and that’s the source of the large relative motion that causes issues.

      • Michael Abrash

        Ben,

        You’re correct – that’s what I meant. If you look at a key on the keyboard and keep doing that while you turn your head, you can easily get your eyes moving at several hundred degrees per second relative to the display.

        –Michael

  • Esse

    “The human perceptual system has evolved to be very effective at detecting such anomalies, because anomalies might be thinking about eating you, or might be tasty.”

    It is not some specific “anomalies detection system”, rather that the human brain has in-depth “routines” to analyse the space & movement, and when you broke the rules the routines fail.

    Like when you are sick in a car.

    So I guess the reaction will not be fear or drooling, more puking.

  • Ben Humberston

    Thanks for the transcript for those of us who couldn’t be there!

  • Mattso

    Yeah, just echoing the sentiments above that having it all transcribed meant I actually got to digest it really quickly. Many thanks!

    Very informative stuff – and here was me thinking it was gonna be easy. :)