I have already talked a bit about this technique that I discovered back at 3DUI 2008 but which was introduced by UNC Chapel Hill. The principle is quite simple:  suppose you have a virtual world potentially infinite, and you want to physically walk this world (with a HMD for example). If you directly apply your real movements to your virtual self, you’ll run into the walls of your small room quite soon.

What’s nice about VR is that it allows you to fool your senses. You’re already fooling your visual sense with incredible graphics (tell me you’re not using a 3DFX anymore!), so why not cheat your sense of movement, which relies a lot on visual cues?

So instead of having a 1:1 mapping from real to virtual, we could modify the translation and rotation speed applied to the avatar. For example, a rotation of the user of 90° would result in a rotation of 100° or 80° in the VE. Same for translation, 1m in reality could result in 1.2m or 0.8m in the VE.

What’s more is that the opposite is also possible : suppose you walk in a straight line in the VE, we could have you walk along a curve in reality!

At VRST 2008, Frank Steinicke from the Muenster University  and David Engel from the Max Planck Institute of Tuebingen each presented a paper on this topic at VRST 2008 : “Analyses of Human Sensitity to Redirected Walking” and “A Psychophysically calibrated controller for navigating through large environments in a limited free-walking space“.

Dr Steinicke’s presentation’s focus was on the evaluation of the limits of redirected walking, whereas M. Engel’s  work is about how to dynamically change the gains of translation and rotation to fit the user’s path in a known environment.

I’ve asked them both a few questions about their work :

> What’s your background, interests and goals with this work ? 

Frank Steinicke : My research interests include human-computer interaction with special consideration on VR, perception and cognition in computer generated environments and visualizations. The goal of this project is to provide intuitive interfaces for exploring VEs. As a matter of fact the most natural way of locomotion in the real world is walking. So, from a computer graphics perspective I am very interested in the question how real walking through CG environments can be realized if only a limited laboratory environments is available. I’m fascinated by the psychophysical phenomena, which allow to trick users, for example, in such a way that they unknowingly move on a path in the real world that differs from the path they perceive in the VE. Of course, we want to know how much we can trick users without them noticing discrepancies.

David Engel : I’ve studied computer science in Tübingen and one of my main interest always has been virtual environments. I first came in contact with redirected walking during a presentation at APGV 2007. I found the idea of being able to explore infinite virtual worlds, like in the Holodeck from Star Trek, very compelling.

> Where does this idea comes from? 

Frank : Redirected walking (RDW) techniques have been used for a few years now. The main idea of redirected walking has been introduced by Sharif Razzaque et al. from the UNC at Chapel Hill. RDW is based on the fact that the visual sense dominates proprioceptive and vestibular senses. This has been shown much earlier, for example, by Alain Berthoz (who gave the keynote talk at VRST).

David : The idea to determine the redirection factors dynamically, emerged from the problems I encountered during my early implementations of redirected walking. As soon as the paths through the virtual environments got longer the errors in the predicted positions accumulated to a point where the users kept running into the walls.

> What are, for you, the most interesting conclusions of your paper ?

Frank : We have identified detection thresholds up to which humans can be redirected in such a way that they do not perceive any discrepancies. For example, we know that we can guide them on a circle with a radius of approximately 23 meters, while they believe that they walk straight in the VE. This guidance approach can be realized by injecting small rotations to one side, which enforce users to unknowingly walk on a circular arc in the opposite direction.

Until now, we have only considered basic walking techniques such as forward movements and rotations. I think these concepts can be adapted to any kind of motion, such as walking on slopes and strafe otions. Furthermore, we have not addressed adaptation, which involves the question how far humans might adapt to redirected walking. Such adaptation has been considered before, for example, with left–right reversed vision, but not in the context of VR-based environments.

David : With a dynamic optimization approach based on the minimization of a cost function we gain a large amount of robustness against deviations from the predefined path and can introduce much flexibility into the redirected walking approach. By adjusting the terms of the cost function we can adapt to new boundary conditions such as the current users sensitivity profile to redirection factors, route choices and multiple users.

On the psychophysical side our next step will be to evaluate the user performance in navigation tasks when redirection techniques are applied. On the technical side we plan to support a more natural exploration of the virtual environment by allowing more complex and branching paths.

> To what extent do you think we will be able to fool the body by taking advantage of its perception limitations? (including other senses than proprioception)

Frank : The same concepts can be applied, for instance, for haptic feedback. Anatole Lecuyer from INRIA has shown that haptic feedback can be induced by visual stimuli, and Luv Kohli has examined how much the haptic feedback may vary from the visual stimuli. Another topic might be the question in how far time can be compressed or stretched in the virtual world and how the perception of time can be changed.

David : The sensitivity of the perceptual system to sensory conflicts seems to depend largely on the amount of congruency between the modalities (e.g. if auditory cues are collocated with the real or virtual world) and the attention given to the different modalities. The extent to which the perception can be fooled might therefore be very task-dependent. In short term the usage of congruent multi-modal input and distractor tasks should allow for a much wider range in which the user can be fooled. In the long term redirected walking techniques could become more sophisticated by taking into account the sensitivities of the user to cue conflicts at different points during the gait cycle. Combining such ideas we should be able to overcome the spatial limitations of the available facilities.

Thank you both for your time and interesting work!

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Their blog publishes an interview of Dr Albert “Skip” Rizzo who gave a keynote at Laval Virtual 2008.

Here are some bits ranging from VR exposure therapies to whether cyberspace addiction is bad or not :

 Albert “Skip” Rizzo received his Ph.D. in Clinical Psychology from the State University of New York at Binghamton. He is a Research Scientist at the University of Southern California Institute for Creative Technologies and conducts research on the design, development and evaluation of Virtual Reality systems targeting the areas of clinical assessment, treatment and rehabilitation.

“(…) [Our] projects span R&D efforts that apply Virtual Reality to clinical areas including: PTSD exposure therapy, neurocognitive assessment, game-based motor rehabilitation and our emerging work with virtual human patients for clinical training. (…)

This presentation [at the MMVR conference] will focus on our development of an inexpensive and easy to deploy webcam-based tracking system that is now good enough to support high-fidelity capture of natural motor movement for interaction within VR game-based physical therapy worlds. (…)

For PTSD exposure therapy, the outcome data from our group and from what I can glean from the VRMC lab, are very encouraging.  (…) From this, it appears that the technology is not the limitation anymore. VR simulations are “real enough” to provide the necessary fear/anxiety arousal needed to promote the therapeutic process of habituation. To be quite honest, it doesn’t take much for a patient with PTSD to get engaged in the Virtual Iraq simulation—their disorder essentially “primes” them to react to the virtual content in ways that folks who have never been exposed to such combat-related trauma, don’t fully apprehend. The real bottleneck is in the training of clinicians on how to properly administer VR exposure therapy in a safe and professional manner. Current VR exposure systems are simply very powerful tools that extend the skills of a well-trained clinician. The challenge is to find enough of those well-trained clinicians to provide informed care for the number of folks coming back from Iraq/Afghanistan with psychosocial difficulties!

(…) [Our] design of the clinician’s interface—a control panel that allows the clinician, in real time, to systematically monitor what the patient experiences in the simulation and to add or take away provocative stimulus events (sounds, sights, scents and vibration) as is required for effecting the anxiety modulation necessary to achieve the therapeutic effect of habituation when conducting exposure therapy. For example, the delivery of scent into the simulation is controlled via the clinician’s interface. We use an Enviroscent system with chambers for 8 different scent vials (gunpowder, diesel, burning rubber, body odor, etc.) through which compressed air is pumped to carry the smell temporarily into the users simulation space.

> What qualities do you see as most important for a realistic/convincing/successful simulation?

(…) Multisensory input, well-designed interface, responsive tracking, flexible ability to adjust software parameters, etc. Also, knowing what type of display format best addresses the clinical target is a key issue. There are some app. areas where full immersion is less relevant, like in many of the motor rehab applications where a nice wide FOV stereo screen works great. However, for all the criticisms that HMDs have been subjected to over the years, I believe they still are the best approach for some of the psychological applications where full immersion is important—and with some of the more recent systems that are available with built-in 3DOF tracking (eMagin, Vusix), they are portable, low cost and can allow a clinician to “do” VR easily in an office setting.

(…) the Novint Falcon force feedback system now offers a new set of options for game-based rehabilitation at a cost of less than an IPOD! We have now developed bimanual coordination games for stroke patients by yoking two of these devices together on a single laptop and some of that work will be presented at MMVR this year.

(…) Even more contentious is the debate as to whether children and impressionable adults will display dysfunctional behaviors due to extensive exposure or experiential play in cyberspace! (…) This literature has produced a lot of small sample size, albeit provocative, one-off studies (just skim an issue of CyberPsychology and Behavior) and a few large scale studies with contradictory results and no shortage of heated debate. This is consistent with the history of similar concerns that have always been raised whenever a new media form is embraced by the masses (film, comic books, TV, video games, Facebook, 2nd Life) or with the rapid adoption of everyday technology-based productivity/communication devices (from calculators to PDA’s to IPhones). (…) somehow the use of pocket calculators never actually produced a generation of children unable to do simple addition!

(…) While there will always be a percentage of the population that will get consumed in any type of media use to a degree that could be consensually agreed upon to be unhealthy, that assessment is still a value judgment. Whether it is a good or a bad thing that I have learned more about the history of the world from watching the History Channel, than from years sitting in history classes in school is a value judgment. Determining whether an isolated, insecure person with poor social skills who finds some connection with other people in cyberspace is further withdrawing from the “real” world or is learning to interact with others in what they perceive to be a safe environment, requires a value judgment. Consequently, no fully satisfying, comprehensive or generally agreed upon answers currently exist for these questions, yet.

(…) I don’t believe that you create a healthy society by limiting one’s choice of media options. Perhaps working to create a healthy society in other domains (better education opportunities, improved healthcare, electing political role-models that are honest and caring), would be a better place to focus ones energies than to blame cyberspace or an individual’s personal taste in media for the ills of the world!

That’s a great way of seeing things, I’m happy Dr Rizzo is taking such positions. I myself don’t know where I would be now if I hadn’t spend so much time with computers during my childhood or if my parents had forbidden me to do so fearing that I’d become a zombie.

But still, you have to watch after your kids’ activity in Cyberspace since they don’t know how to regulate it themselves.

He also confirms what I’ve been saying for quite some time now,  we have good enough hardware but we don’t make the most of it!

If nobody is doing it I’ll have to do it myself ..

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As you can see, they have the same old LCD screens with only a few determined positions as good ol’ donkey kong, except it’s stereoscopic!

You can buy some here and on eBay.

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Along with Assassin’s Creed vastness and beautiful graphics, Gears of War 2 with its violence and majestic landscapes, the latest game by the swedish editor Dice, Mirror’s Edge, would be a great way to feel freedom and wind on your face as you jump buildings :

This Wired review explains why the game feels so immersive:

It doesn’t do justice to call the action in Mirror’s Edge “intense”: It quivers, like a hummingbird, and your first-person view is constantly whipsawing like a paranoid cameraman hunting for the best shot. (…) What makes Mirror’s Edge so different? Sure, the action is swoopy and vertiginous, just as it is in many other games. (…)  Why does this game get its hooks into my brain so effectively? Why does it feel so much more visceral?

I think it’s because Mirror’s Edge is the first game to hack your proprioception.

That’s a fancy word for your body’s sense of its own physicality — its “map” of itself. Proprioception is how you know where your various body parts are — and what they’re doing — even when you’re not looking at them. It’s why you can pass a baseball from one hand to another behind your back; it’s how you can climb stairs without looking down at your feet.

Most first-person shooters do not create any sense of proprioception. You may be looking out the eyes of your character, but you don’t have a good sense of the dimensions of the rest of your virtual body — the size and stride of your legs, the radius of your arms. At most, you can see your arms carrying your rifle out in front of you. But otherwise, the designers treat your body as if it were just a big, refrigerator-size box.(…)

When you run, you see your hands pumping up and down in front of you. When you jump, your feet briefly jut up into eyeshot — precisely as they do when you’re vaulting over a hurdle in real life. And when you tuck down into a somersault, you’re looking at your thighs as the world spins around you. (…)

The upshot is that these small, subtle visual cues have one big and potent side effect: They trigger your sense of proprioception. It’s why you feel so much more “inside” the avatar here than in any other first-person game. And it explains, I think, why Mirror’s Edge is so curiously likely to produce motion sickness. The game is not merely graphically realistic; it’s neurologically realistic [Cb: I’d like to have a neurologists opinion on that!].  (…)

It’s an interesting lesson of game physics: When you feel like you’re truly inside your character, speed suddenly means something.

The opposite is also true. Without a sense of physicality, speed feels lifeless. In Halo, you’re playing as the cyborgically enhanced Master Chief, so your top speed at an open run is — according to Halo nerd canon — 30 mph or something. But it doesn’t feel very fast at all, because your avatar doesn’t appear to be actually exerting himself.(…)

The combat in Mirror’s Edge felt more believable than doing battle in Halo, too. When the cops were shooting bullets at me and I was frantically racing to escape, I kept thinking: “Damn, I’m going so fast I might just escape!” In most first-person games, I usually wonder the opposite: How are these guys not hitting me? So the brilliant physicality of Mirror’s Edge isn’t just a boon to the game’s physics. It also makes the narrative and drama more plausible.

So you feel like you’re the character, this means more presence, so more immersion.  I have to talk to them.. Sweden is not so far from Paris and I guess I’d take less time to go to Stockholm than to go to Velizy =)

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Going from 15mins of bike to 2h30 of public transportation daily doesn’t really make me happy (to stay polite).

Anyway, today we met Matthew McGinity from iCinema, and he’s been showing us what they’re doing there; it’s really impressive and technically challenging! And it’s always nice to meet people that you’ve known only through mails. And Australia seems to have much more sun than Velizy…

And no they’re not doing what you’ll see below..

To come back to the topic that I’m sure will raise your interest (you.. geek!), here’s at last an “ARotic” application, maybe the first AR projet that will make money =)

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A real problem anyone dealing with virtual humans should be aware of.

And  one last thought for great author Michael Chrichton who died on tuesday..

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I really feel that it’s becoming easier to get a nice VR setup at home. The minimum that we should have is head tracking and one hand tracking. From that point on, we only have to use the mod capabilites of games and play VR!

Hum that’s the theory, practice is another thing, but let’s start trying!

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 From Clickz, just a nice example of using finely sprayed water as a screen, “part of a promotion for an upcoming movie release” :

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