@Palmer
I was caluclating for a circle 6foot diameter, (3foot radius)
to calculate the area of a circle with a 36" radius then it is Pi*36*36=4071 square inches, sinc each ball bearing is 1" I based it on that for my rough calculations (I did not take into consideration for the casing) but for a 6foot diameter circle you would need at least 2000 of the ballbearings.

Do you think a 3foot diameter circle is big enough? swing one of your legs foward to maximum stride, measure back to the other foot, double that and that is roughlyu how big it needs to be for you.

Palmer - I didn't realize that. (Who in their right mind would choose a gamepad over keyboard/mouse for an FPS?) Determining arbitrary directionality via limb motion could get quite complex given the numerous possibilities. I believe if the system was well implemented that it would be the most accurate and flexible, but it might take a long time to work out all the complexities. A more direct solution might be just using an overhead IR or pulley system like you mentioned.

Of course this is all just wild arm-chair speculation. This omni-treadmill thing-a-ma-jigger is a real long-shot anyways. Don't waste too much time on it, because what we all REALLY need are the detailed PR3 build specs!

It would not be enough for running, but it would be plenty for walking at a reasonable speed. The goal would be to keep the center mass as close to the center of the treadmill as possible, and I think 3 foot diameter would be enough (That is larger than the Cybercarpet, for sure).

@Brantlew: I am working on an ever better version right now, I want to make as many improvements as I can before writing it all up. I am going to be laser cutting the shell for this one, so it is going to be as small and lightweight as possible.

EDIT: And yes, I know that walking is not as fun as running. But it makes more sense to see if this even works first! If I did this myself, I would probably order barely enough bearings to make a long, narrow strip. That way, I could make a single direction treadmill out of them, and see how that goes.

A top down IP camera sounds good in theory but how can it determine anything other that which direction you are facing? I'm not sure it will be able to tell if you are walking fowards/backwards or strafing if you are essentially stationary because the "cyber carpet" is keeping you in place as you move around in the virtual world. possibly a custom skeleton tracking setup with 2-4 IR cameras around you and wearing a "suit" that has IR LEDs at each joint would allow for fairly accurate skeleton tracking, just the software to convert the data to WSAD or analogue signals that can be used in game would be the hard part.

EDIT: If 3 foot is enough then a 3foot diameter circle of bearings would require roughly 850 of the ballbearing assebliiles (by square inch calculation/ 1.2) so much more affordable I was worried there for a mi!nute

This typ might be easiear to mount:
http://newzealand.rs-online.com/web/p/b ... s/0687770/

if they can be found much cheaper

EDIT:
Here's another possible option:
http://newzealand.rs-online.com/web/p/b ... s/0408536/
Omni roller! much cheaper than the ballbearing units and you would need less of them... (although questionable about how much weight it can handle)

I was thinking of a top down IR just to detect off-center movement. The carpet can't keep you perfectly in place. There would be some displacement from the center - even if it's shaky. So basically it's similar to the harness-pulley system except it's optical instead of mechanical - a short-cut for determining direction of motion instead of limb analysis.

Other characteristics like gait speed and body direction could be determined by other methods (Kinect, pedometer, IR, etc).

I think if you are going to do limb tracking of any kind, you get a head-start by using the Kinect because it already converts the signals into high level joint objects for you. Going for a lower level IR solution to track joints means you have to start from scratch.

The CyberCarpet uses 4000 balls and I think it is too small. I would want something bigger. The only affordable way to do this would be to use the same method they did - placing loose balls in a custom grid. To prevent them falling out, a second layer with holes slightly smaller than the diameter of the balls could be placed on top. How much would it cost to have grids cut, out of plastic or metal? Maybe $300 or $400? And the balls themselves should be really cheap. The ball changers might be better but they are too expensive, unless the cost continues to decrease - would 3000 cost half as much as 1500? How about 6000? 9000? 12,000? I would want a surface two or three times as large as the CyberCarpet, at least. I would like to be able to run.

http://www.vxb.com/page/bearings/PROD/Kit7760

@Aphradonis: The problem is, loose balls in a grid do not spin freely, they have quite a bit of friction. These units I linked to rest on a bed of ball bearings, which is why they would work passively. The cybercarpet only works because it has an active treadmill underneath that is bearing most of the weight, instead of the plastic grid.

I mean, for an active solution, the Cybercarpet could work, but it would definitely not work as a passive solution. As for prices, I do not think that it would possibly go under $2 per bearing.

Hey guys, I think I figured out a way to get really accurate direction and speed tracking - at least for walking. When I first thought about using the Kinect I thought in terms of recognizing different hip and leg "gestures" and translating those to motion commands. That gets complicated because there are so many ways you can move your legs to locomote. I think instead you can just ignore the legs entirely and just concentrate on the feet position. When you walk one foot is always on the ground. So all you have to do is identify which foot is planted and then calculate the velocity and direction of motion between the raised foot and the grounded foot. That will be your motion vector! In normal walking the grounded foot position is constant and all relative motion comes from the raised foot. On a omni-carpet, both feet move but the "relative" motion should still be approximately the same. So walk anyway you like - sideways, bow-legged, angled. It doesn't matter because the relative foot positions are all that matter. It simplifies the problem tremendously. I would have to get a Kinect to prove this, but it seems like a really easy problem now.

Maybe can consider this pre build ball table. Just ask them not to install the leg.

http://www.alwayse.com/en/products/ball_tables.html

Or can we consider using the same ball but we build it like a roller skate and build a slightly curve circle using wood to walk in? In this case we don't need that many balls, just enough to cover an average shoe size.

I thought I read the CyberCarpet can be driven actively or passively. Even actively, wouldn't it be cheaper still? 4000 ball changers would be $8000. And 4000 is barely enough. Still, ten or twelve thousand or so for omnidirectional motion is a bargain compared to $50,000-$100,000+ for an ODT. I hope a CyberCarpet could be done for $5000.

Here's a news article about the CyberWalk ODT, incorrectly called the CyberCarpet. Palmer - you said no ODT could ever perfectly match a free range for VR. Not quite; a 100x100m ODT would be imperceptible from walking on solid ground. At least 6x6m eliminates the feeling of walking on ice. Hopefully in a few decades large chainbelt ODTs will be an affordable investment or DIY project - $15,000 or less. For now a ball carpet is the best (well, only) practical solution.

@brantlew: Yes, that is genius. The vector of the raised foot from the planted one will indicate which direction and at what velocity you are moving. I imagine the Kinect could do this (line of sight issues not-withstanding) but you could also attach a Wiimote to each shoe, or even some custom IMU type stuff. I do kind of like the idea of modding a sneaker to have the sensors right in there: cyber-shoes!!!! But the Kinect would probably be easier since there is already a lot of open-source code to work with it. However I know there is some lag with the Kinect, but its probably not so bad.

Excellent ideas, pierreye! So essentially CyberCarpets already exist as commercial products! I had no idea! The largest is 7x4ft (approximately 300mm in 1ft)! That's great. How much do they cost?

I also like the idea of putting the balls on the soles of VR shoes. Like those powered skates but omnidirectional instead of bidirectional. That could be an ultra-cheap, compact solution. Like under $1000 for serviceable omnidirectional motion in place!! Wow!

YES!!! Putting the balls on the shoes! Another genius!!!

Here's a ball transfer table for $666. It's way too small and the spacing between the balls looks too big. A large enough table must cost thousands, and finding one with small enough balls might not be possible. Let's keep looking. It seems hard to find info on them. Pierreye's ball shoe idea might be the best way to go.

Yup, those ball tables would be good if the density was higher, I have not been able to find any with closely spaced bearings.

Putting balls on the bottom of the shoes could work, but it seems like it would be akin to walking on rollerskates. You would almost certainly need a harness, hard to know without trying. It seems like it would be pretty slippery!

And yes, an enormous ODT would be better than an open space; But I don't think they are going to become practical anytime soon. Industrial machinery has always been expensive, and there is no real way to cut costs further; As an investment, it could make sense (For people who have the space, or a business), but I am not sure it would ever happen as low as $15,000. Hopefully I am just being pessimistic.

I would definitely use a harness. I think ball shoes on a shallow dish with a harness is the only affordable option. I meant a small ODT for $15,000, like 6x6m. If they are $50,00 or less today, in ten or twenty years the price could be $15,000 or less.

@Pierreye
Shoe idea so simple, its a great idea

@palmer
assuming you are using the same balls on the shoes as you would have been mounting to the base then it should be the same "slipperiness" I don't see how its any different.

The only cons I can think off is maybe the shoe might be quite heavy. Or we only mount the balls near the edge of the shoes to cut down the weight.

There was some discussion of roller shoes at the beginning of this thread. I'm still a bit skeptical about the idea. It just seems so slippery and ungainly - like walking on roller skates. At least it's cheap to try.

If there was a way to add some resistance to the balls then maybe that could help. At least then you could shift some of your weight onto them and feel the mechanics of walking a little better. Maybe then you wouldn't need quite as much harness support either - more like a safety rope instead of a balance assist. The bowl idea could complement this nicely. If the resistance were calibrated so that the shoes were fairly steady on flat ground but would roll on the incline then that might create a stable system.

We could use undercarriage spray that will coat thin layer of rubber on the steel ball to increase resistance.

@Cyber - You wouldn't need to attach wiimote to shoes, just tiny IR LEDs. The WiiMote is the camera that tracks them. Still - there is some work that would need to be done to translate those moving lights into accurate 3D coordinates. I say just use the Kinect and grab those coordinates for free, plus you get all the other body position information along with it like hip placement, torso orientation, head height, arm placement which could be useful for other things.

I'm curious if the Kinect lag is due to the processing power of the on-board Kinect computer or the sensors? The OpenNI demo was interesting because it really seemed to be accurate and real-time. So maybe the solution to lag is bypassing the Kinect CPU and doing those computations on the main computer?

All of a sudden I've got an itch to buy a Kinect now.

Good idea. I wonder if the rubber would just rub off though. How about using plastic or even solid rubber balls?

@brantlew: I wasn't suggesting the use of the IR camera on the Wiimote. It also includes a 3 axis accelerometer, among other things. It tracks relative motion. You actually don't need the absolute position. All you need is that vector between the two feet, which the accelerometer and some simple math would provide.

@Cyber: ok, I see where you are going with that...

What about using steel balls but putting rubber matting on the inside of the dish? The same interlocking mats they use in weight gyms. As a bonus - it would cushion your fall

If mounting the ballbearings to the floor and walking on them is ok then mounting them to your shoes and walking on them should be exactly the same, the amount of friction between you and a stable surface is the same in both cases.... what it all comes down to is how much friction those Ball Transfer Units actually require to move them.
Coating the balls in anything probably wont work because the casing would scrape it off again and if any bits got stuck inside the bearings then you'd have bearings with uneven friction which would cause problems of its own, I think you could spray the rubber onto the curved surface you are walking on to improve grip of the ballbearings to the walking surface which should remove any "slip" where the bearings are just sliding on the surface instead of rolling on it.

EDIT: @Brantlew I think a Rubber mat could work as long as its not too soft

I have some hard rubber mat that use for outdoor playground. I could test it out once I source out the ball transfer units from local supplier. I estimate my cost would be around USD 200 for the whole project.

The problem with roller shoes is more complex than it seems. It is definitely not the same as having the balls on the floor!

For one, you would be elevated pretty high above the ground, even with smaller transfer units. Ever try running in platform shoes? Ask your girlfriend, they will explain.

In addition, normal shoes flex quite a bit when you walk, and even more when you run. Having the shoe be a hard, solid platform with balls on it would be pretty hard to walk on/keep your balance on!

I suppose it could work, maybe I will try it out. That bearing supplier I found is the cheapest I can find, and it turns out that they are based less than an hour drive from me, so I could even do local pickup. I don't expect it to work as well as an entire floor, but it might work well enough.

The shoe idea is the only option that is affordable. Tens of bearings are affordable, thousands are not.

@palmer
have you ever worn military issue boots? they are not all that flexable, its not like soldiers are running around in nike running shoes but i get your point

maybe we can use these bearings:
http://www.vxb.com/Merchant2/merchant.m ... sfer-Units
or these
http://www.vxb.com/Merchant2/merchant.m ... sfer-Units
and counter sink them into some boots with fairly thick soles to keep the height to a minimum sure they will be a bit stiffer than normal shoes but I think its worth a try, the cost saving will be massive if we can use "cyber shoes" instead of a "cyber carpet"

The shoes wouldn't have to be flat and firm. They could still bend. The bearings could be attached individually so the shoe would flex. The height would be an inch or two extra, not much. Less than rollerskates.

I like mAchiNE's idea of using lower profile bearings and sinking them into thick soled shoes to minimize the height impact. The second unit looks more realistic to me since the first one is so wide that you would not be able to fit many together. These are all really large bearings (1" or so). At that size we could only get a few of them on there and they would really be more like rollers skates. Have you guys run across any smaller size bearings - maybe in the 1/2" range?

This is a rather wasted thought, but how about a smooth/teflon type surface, under which sits 2 electromagnets on 2 2 DOF frames (like cranes).
The use could wear shoes with metal plates in them, and when he walked forward, the system would 'slide' him backwards by applying force to the foot that is stationary.
You could call it the MoonWalk

I know this is not what we're all looking for, but what about something MUCH more simple and practical. What if you just got a cheap motorless treadmill and a Kinect.

http://www.sportsmansguide.com/net/cb/Stamina-InMotion-Manual-Treadmill.aspx?a=407557&pm2d=CSE-SPG-3-GOOGLE&utm_source=google&utm_medium=cse

You would be limited to just forward and backward motion, but it would be very natural and unimpeded. No weird shoes or balls to slip on. No complicated construction. You might attach a safety cable in case of a fall but it wouldn't need to be load bearing. To track speed and direction, you could use some type of mechanical odometer or the Kinect API. The only thing left would be turning. You could use a simple gesture like torso twisting to accomplish that - ie. turn your chest left and you turn left, face forward and you stop turning. That could be tracked either via Kinect or IR sensors.

I know it's not the perfect solution but it accomplishes some of the core goals - realistic locomotion, inexpensive ($350), and trivial to implement. Would the simplicity and price of this system outweigh it's limitations. Personally I believe so.

Update: I'm not sure how much force you actually would need to start the belt rotating. It might not be possible to just start walking and have it turn. Near frictionless rollers would be necessary. Maybe you could mod an existing treadmill or maybe you could build something easily.

@WiredEarp: I had thought of a similar idea, but maybe cheaper and more practical. What if you were in a circular pod (like a metal hula hoop size) and had your feet tied to resistance bands. So you could pick up your feet, but only move forward and back slightly (then it would pull you back into position). The metal hula hoop could spin within the pod, to allow you to freely turn. But the idea would be that you just couldn't leave the circle. You would pick up your foot and "think" you moved it forward, but the resistance bands would absorb all the force and return your foot the the floor in the middle. Seems like it might be dangerous, but I think somehow it could work.

@brantlew: Honestly, that idea (which has been discussed before) is the most obvious, practical, and affordable one out there. The main problem is that its not omni-directional, so you are limited to only moving forward (I don't think you can go backwards on those things). I have tried one once, you can walk at different speeds, you don't have to run. It would still be better than using mouse and keyboard, but I am not sure it would be any better than using a wearable setup where you could turn freely, but had to walk with a gamepad. So far in my experiments, being able to freely turn with a wearable VR setup is a big factor in adding immersion. Using a manual treadmill would give that up. But I guess you would also get something in return. The biggest benefit to that setup would be that you could use wired peripherals, meaning the HMZ-T1 (without hacking), a powerful desktop machine, the Razer Hydra, etc. All things that are ready to go off-the-shelf. About the only custom software you would need would be to map the treadmill motion to the 'W' key, which seems trivial compared to the other stuff that has been discussed. Hmmm....

@Cyber: It certainly would be a tradeoff? What's more important, real turning or real walking? I don't really have any experience to judge from. I guess it depends on the application. I would be interested to know how natural the turning mechanic could become once you got used to it. Twisting your body at least resembles the real world motion versus pushing a joystick which in no way resembles walking.

Having thought a bit more about it I realize that I didn't think through a lot of the details. For one, you're right - those treadmills don't go backwards. Also they are hard to start moving and once moving they continue moving if you just stop immediately. Palmer's Curve treadmill looks like the right solution but those things are $5,000!! So for a usable system you might still need to build a custom motorized and computer driven treadmill - similar to things we have discussed elsewhere in this thread. The difference being that you only have to work in one dimension which simplifies the task a lot.

Edit: As far as mapping motion to the W. If that's the best we can get then I almost don't see the point. The reason you feel immersion from real turning is because it maps 1:1 with your body. Mapping 1:1 with the walking speed and motion should be the goal and I bet would be equally immersive.

A bidirectional treadmill has advantages. Manual treadmills can be had for less than $100, and they can be used to walk on backward and forward. I originally envisioned using one in the simulator I've planned, but cyber got me thinking being able to turn is better. However, people who used the GameRunner prototype said they felt very immersed. Feeling the sensation of walking normally through cyberspace is very immersive. Of course, so is turning. It may be we have to choose one or the other, realistically. Perhaps turning in place would be better for games like Call of Duty and using a treadmill would be better for The Elder Scrolls V: Skyrim. FPSes require twitch play, so turning happens alot more and alot faster. RPGs are slower and involve more walking over long distances, so I think a treadmill might be better in that case. And with a standard treadmill wired devices can be used. It's a complete plug and play solution. It doesn't get any cheaper or easier.

Rowan Underwood goes jogging - in Cyrodiil! For serious running, though, I don't think you can really use an HMD. You'd need a monitor or projector.


How does this ODT work? Do the belts bend? It looks different from other ODTs with wider belts moving perpendicular to the chain.

I have seen that, and I think that it does not work.

Watch the video closely, 90% of the walking is in only two directions. He never travels more than a few feet in other direction, and always turns back to one of his primary directions very quickly, or backs up. I think he knows very well the limitations of the design, and that video is made to try and hide them.

EDIT: Never mind, looks like I am wrong. Pretty suspicious video, though! Check out here: http://www.vsd.bz/

EDIT AGAIN: Okay, maybe I am right. No explanation of how it works beyond that single diagram, no pictures or video of behind the scenes, and that video he posted on youtube still has the limitations I outlined.

@Aphradonis: I agree. I think slower paced games like SkyRim would definitely benefit more from the walking mechanic.

I was actually thinking today of a hybrid solution for Second Life where you would jump on a treadmill to explore but then be able to hop off and freely move within a small 8x8 square when you are just hanging out in one place. Admittedly would suck for most games but for purely academic VR its "ok".