Tom Forsyth, Software Architect at Oculus VR gave a talk at GDC Europe on Tuesday entitled “Developing VR Experiences with the Oculus Rift”.

In it, he echoed a lot of the sentiments from Sony’s own talk earlier that day, but he also delved a bit deeper into physiological phenomena that impact development for VR.

Be kind to your players

Tom kicked off by emphasising the point – be kind to your players. VR Developers are poor judges of what is good for VR. Spending all day in and out of an HMD, looking for bugs causes their brains to acclimatise and learn to “ignore the crazy.” By contrast normal people’s brains are fresh and innocent – so much better at judging whether or not your experience works and isn’t too intense. Like Jed from Sony, Tom mentioned that if you give in to the temptation to crank all the action “up to 11” you are likely to traumatise your players to the point that they will want to stop playing.

Every player is different – what will be intolerable to one player might not even be noticed by another. Tom also mentioned that there is no one simple sliding scale of tolerance. For example some folks are sensitive to stairs, others not. Indeed, some people find going up stairs is nauseating but are fine with going down them, whilst for others the converse may be true. Everyone’s sensitivities are different. Although, of course, some are super-sensitive to everything (e.g. Michael Abrash, who apparently used to get motion sick when playing Quake on an old CRT monitor!)

Tolerance can not be built up within a single session in the way you might create a difficulty curve for a game. Indeed, pushing too hard can send the player on a negative feedback spiral.

In summary, err on the side of being gentler – even if you don’t make people sick, they are still unlikely to take in plot and game mechanics if it’s too intense. They’ll just be holding on for dear life. Here, again, Tom referred specifically to Jed’s talk which proposed allowing the player to skip or scale down the intensity of the action; adding to that by suggesting things like reducing in-your-face particles and explosions or that action can be slowed down by reducing the scale of the world.

If you are going to implement variable intensity then you should default to low – allowing players to opt-in, rather than opt-out. Furthermore, you should make it easy for the player to change these settings at any time – so you can dial it back (or up) during play. Bear in mind that a more relaxing experience is a more immersive one!

Physiology – The Vestibulo-Optical Reflex, IPD & Player Height

Tom went on to talk about the Vestibulo-Optical reflex (VOR). This is the phenomenon where when you turn your head, your eyes automatically turn in the opposite direction in 1:1 ratio to stabilise your view – so if I turn my head 10 degrees to the right then my eyes will turn 10 degrees to the left. The issue is that optics impact the “VOR gain.” This is one of the reasons why it takes a while to adjust to new glasses, that alter the scaling of your field of view – with new glasses, when you turn your head 10 degrees you might find your eyes only need to turn 5 degrees to compensate. The brain does make this adjustment, in time, but optometrists say this can take around 2 weeks – not of any use to VR developers. What does this mean for VR? Just that you should not adjust the field of view scale, as you can do in monitor games, where the player has the rest of the room as a reference – field of view is set by the SDK for the player – developers should not mess with it!

Another thing you can not take any artistic licence with is the players Inter-pupillary distance as this is a property of the player and, again, set by the SDK. What you can play with, though is world scale by scaling down the centre-to-eye distances and head motion by and identical ratio. This creates a compelling sense of being larger or smaller. As mentioned before, this can also reduce intensity for some players by scaling down accelerations. It is possible to go too far with this, but as a rule a factor of 2 should be fine. Weirdly, early studies in the field suggested that reducing IPD to zero was a good way to minimise simulation sickness but this has not been borne out by any Oculus VR studies – so don’t do it.

Another thing that you can do take artistic licence with, without worrying too much about disorientation, is the height of player. Tom then launched into a series of examples using Geordie LaForge taking on the body of Commander Riker, which were a joy for the Trekkies in the audience (who were certainly in the majority), although I feel compelled to point out that he misranked the Lieutenant Commander – calling him Ensign! Tsk, Tsk…

One fascinating point that Tom raised on the subject of player height was an issue arising from the problem of having a seated player. Apparently when your feet are touching the ground, this touch stimulus takes precedence over your visual sense – so instead of thinking you’re 5’5″, your brain remains convinced that you’re just 4′ above the ground, and then goes on to judge all other distances based on this scale – this creates some strange scaling effects, causing objects to appear to change size depending on what you’re focussed on. There isn’t a one-size fits all solution for this problem. You could design your game with seated avatars, but obviously this isn’t much of a solution for a lot of experiences. You could try scaling up the world to compensate for this effect, but then you’re really just creating an even greater mismatch. Another option is to have players sit on chairs where their feet don’t touch the ground, but this may not be practical for all situations. Luckily, while it is a little strange, this effect isn’t actually nauseating, so you can simply give in and accept that, for the most part, the player will experience a somewhat scaled down world – this will at least be a more relaxing experience for them.

Transition animations

Reemphasising “Rule 0” of VR, never take control of the players head, Tom discussed how to handle transition animations. Sometimes transitions need to happen, for example

– getting in and out of vehicles, beds etc

– standing up after being knocked down

– picking something up off the floor

Normally this would be handled by a player animation, but obviously this breaks Rule 0. If you need to transition a player then you should always telegraph it. Other techniques include:

– show the avatar doing it by transition carefully to 3rd person. One thing you could try here is to use a try a ghostly/translucent avatar for something like leaning down to pick something up (where the avatar will eventually reconverted with the players head position)

– Dissolve or fade to black, although it should be stressed that you must maintain tracking as this happens – don’t just freeze the screen.

– the third suggestion was the most interesting – use a ‘Blink’ effect by bringing fuzzy edged black borders up and down over the players view (as if theyre blinking) – close eyes, teleport them where they need to be, then open eyes. Apparently this feels completely natural and if its done quick enough, (around 300ms) some players barely even see it. Indeed, sometimes people don’t even notice that the teleport has taken place – they simply report that they “got in the car”!

Avatar animations

Even though these can be a pain to do, they are really cool, even if they’re not mapped to you perfectly. Some good examples from TF2 include:

– High fives – looks much better in VR than on a monitor

– Yelling ‘Medic’ – brings a hand to your face

– The Sniper’s bird

– Seeing a your own shadow

But you must always remember “Rule 0” – never mess with the camera. Toms solution is ‘the meat hook avatar’ – which is essentially a decapitated avatar that ‘hangs’ off the players camera position. This works fine, and is very convincing, so long as the player can’t see themselves in the mirror, or their headless shadow on the floor!

Maintaining high frame rate

To finish the talk, Tom emphasised that on the DK2 you MUST get a rock solid framerate of 75hz at all times. You should aggressively drop details to achieve this. Never drop frame rate, and alter your production pipeline to get this frame rate throughout production so your designers can test properly. He went on to talk about the main costs to speed – Draw calls and Fill rate – although I must confess much of this went over my head so I’m unable to adequately report it.

Q&A

When pressed on the subject of Oculus VR producing their own hand tracking solution, Tom got very coy: “I would get in a lot of trouble with my boss if I answered that question,” he went on to say that hand tracking is a tough problem, there are lots of other companies working on it and Oculus “would love to see it solved and we’ve just received a lot of additional resources from theses kind people [Facebook]. But I didn’t answer that question.”

Make of that what you will.

Should Oculus get into certification of games, around age ratings and comfort levels? They are publishing some titles but are very reluctant to get into certification for the reason that they do not have all the answers themselves.

When do you think VR will be used mainstream on a day to day basis? Tom talked about VR desktop applications and how he would love to try to use one for programming so he wouldn’t have to alt tab between windows, but resolution is still too big an issue to allow that at the moment. He did note that resolution is rapidly improving, invoking Moore’s Law, but did not speculate as to when it would be good enough to be a viable replacement for monitors.

Someone suggested that CV1 should have a sliding panel at the bottom to allow you to glance down at your keyboard for some apps. Tom said that Oculus have done a lot of experimentation around allowing users to see the outside world, either in hardware design (such as what was suggested) or via a camera. He confirmed that this was the main point of the USB port on the front – so folks could experiment with a camera for AR and other real-world awareness features. The determining factor though is weight and, to a lesser extent, cost.

When asked about users with vision problems, Tom did discuss that Oculus VR are looking at the cost and design implications of a clip-in insert that will allow visual correction for things like astigmatism and near-sightedness, which can not be corrected with the packed in lenses (or indeed any wide FOV lenses). The military have been using this solution for several years.

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