Something I've been thinking up is not really the game itself, But the way your control it/get immersed.

So here is my idea.
SAO is Sword art online (Since i say it a few times in the description)
~
A VERY basic grass area (Looking all pretty and realistic) Just flat, No hills (maybe the sky box can have some) And some walls that you can see when you get close to them (To stop you from bumping into the real ones.)

Now. How the game play will work... First, You would need a warehouse (The same size as your level (Of course this would be no problem since you can just change the flat levels design))
Then you would need a decent scan of yourself. (+Every movement you could ever make) So a 3D model.
Something like the Oculus Rift. For visuals.
sensors for your hands fingers toes (Basically a modeling suit) So something can track your movements exactly.
Maybe some sort of wind device (To simulate wind)
A fake weapon (In the real world, So it feels like you are holding something "I don't know how to simulate feeling, This isn't SAO >.>")
And (Optional) Someone to save your ass just in case you are about to walk into a real wall. ((((This is what the In-Game walls should do anyway))))

Okay, Now onto GAME PLAY

Walking would be as realistic as possible, (Making the In-Game model copy you precisely) Same with running, crawling, rolling, farting and sneezing etc etc.

Since we are making you carry a fake sword/gun/weapon<<< We could render a beastly awesome one in game to match maybe with fire coming out of it. (If its a sword that is, "Maybe i am thinking of SAO Q.Q")
We could Indefinitely have other players (They would have to wear the same silly getup as you though)

The OVERALL idea would be. While INSIDE the game you can get a menu (That opens the same way as SAO farrrk) Or through some other command like a button on the Occlus Rift, Then you can build a fantasy world inside the flat area, (Now we are going garrys mod....). Of course, Since you are walking around with a real body, Going up and down wouldn't work so well But building a huge castle with one floor would still be awesome. (Or something like that)

The best part about it would be, It doesn't have to be (Flat land on the earth!!!!) It could be a huge floating island with waterfalls and stuff too. The overall idea for the level would be yours. Same with how you can interact with it, If we could implement a suit with force feedback, we could even have it feeling like you can punch through walls
(Eg if you punch a OBJECT the force feedback will stop your arm on the object) Causing the object to crack, or shatter or turn to dust >:, Of course you don't want to be punching the ground, cause that would ACTUALLY hurt your hand xD

But you could also build a level that just looks pretty (I know this sounds VERY unrealistic) But you could use your house as a reference model and wear the suit around your house. then you could basically have augmented reality for you house "On a more realistic note this WOULD be doable but would probably take you ages to get the house right.)

This can be expanded in so many different directions, And i don't want to make a TL:DR post. So I'm going to stop now. But you guys catch my drift right?

(PvP would OBVIOUSLY be forbidden (Unless you are playing internet wise then you could have 2 people in seprate areas)
If you were playing Lan, You would be smacking the real person with a sword, and that would suck (For the other person "Evil grin")

Although i guess it would be fine for a gun (Fps type match)

Could be cool to blow up your house too lololol

I think the general term for what you're describing is "augmented reality" -- or more specifically in this case "spatial augmented reality" (or "video mapping"). I don't know of any implementations that rival your described game, but it's definitely something people are working on, and there are already some fairly impressive things out there. The technology probably isn't quite there for exactly what you're describing yet, but it's an interesting idea.

Although it doesn't share this type of input -- or for that matter necessarily use computers at all -- you might also be interested in the "real life shooter" Patient 0, where players proceed through a series of professional lit and designed sound-stages populated by actors in screen-quality make-up.

What you are saying is close. Augmented reality seems to fit better. (It completely replaces your feel of realty, and puts you inside another's fantasy.)

Imagine a warehouse, Dark, (So dark you cant see anything) But when you put on the "Oculus Rift" Or whatever you are using, All of a sudden you are (Still int he warehouse) But the warehouse has been scanned by a 3d imager (Moved objects from the real world into a model on a computer) All lit up, Full of Npcs, Or shells (Basically mindless people that ignore your existence) and there some sort of classical dinner going on.

I'm not asking that you can interact with the world, Just more or less be able to walk around in it.

As a concept of course.

~Edit, Spell checking.

Well, when it comes to melee, what I had thought ages ago was using two mice (if possible) , one for sword, one for movement/shied etc, there might be room for gestures. It may not be super ideal, but hey anyone can easily get two mice, no need for special equipment for a game.

This has nothing to do with my post xD

If my idea was to work, and be produced. (Not happening Lololol)
You wouldn't need a mouse, Your arms would be holding the shield! (And the sword)

Still pvp would be a pain, So you would have to make 2 huge ass rooms lol.

Ill see if i cant make some photo's later.

I'm pretty sure hundreds of people have had this same idea, but it's pretty darn costly to implement

VR and motion capture keep getting cheaper though, so maybe one day soon it would be feasible. Like you say though, you'd also need to rent a huge space to host the game, which would have to be close to a metropolitan area in order to get customers, which is another huge expense. Then on top of that, there's the actual game development part!

I had the same idea when I was a teenager, but as an FPS instead of a melee game -- other players could be in the same arena as you, and the VR goggles could draw 3D models for them using their exact poses, so they line up with reality. You could then play with a laser-tag gun, which is registering shots against their real-world body.

Having walls and obstacles in the arena would be fine, as long as your motion capture and VR tech is accurate enough that it can draw virtual walls in the exact same places as the real walls are.

To build this, you would need an existing, talented games studio that can build the software, and you would need a bunch of hardware engineers to concoct your VR environment for you. Each of those teams would then need millions of dollars in each of their budgets... And then you'd need to attract enough players, and charge a high enough price to make back your money.

At the moment, it's probably cheaper to scrap the whole VR part and just use reality, like Patient 0 did:

I've seen this. Looks interesting. But not quite what I'm after, We are going back to interactive.

I'm going to clarify some things in your post.

1.

Like you say though, you'd also need to rent a huge space to host the game, which would have to be close to a metropolitan area in order to get customers, which is another huge expense. Then on top of that, there's the actual game development part!

This is not entirety true, You would only need to hire a decent sized warehouse (Like an aircraft hanger <-- A little on the big side). And sure, It would cost a HUGE amount. But it seems more likely then some would admit.

2.

I'm pretty sure hundreds of people have had this same idea, but it's pretty darn costly to implement

Upon thousands, Of thousands, And thousands.....
&

To build this, you would need an existing, talented games studio that can build the software, and you would need a bunch of hardware engineers to concoct your VR environment for you. Each of those teams would then need millions of dollars in each of their budgets

As for the cost. I'll get to that in a sec.

3.

I had the same idea when I was a teenager, but as an FPS instead of a melee game -- other players could be in the same arena as you, and the VR goggles could draw 3D models for them using their exact poses, so they line up with reality. You could then play with a laser-tag gun, which is registering shots against their real-world body.

Your thinking of a GAME again, I'm only talking about implementing the SYSTEM and the CONTROLLER, Not actually making a game. Although that would be freakin sweet, for now I'M skilled enough to make a small 3D grass world. (And i suck at everything.)

4.

Having walls and obstacles in the arena would be fine, as long as your motion capture and VR tech is accurate enough that it can draw virtual walls in the exact same places as the real walls are.

Instead of making the VR software draw the walls, Why not make a substitute (That runs along with the system) Do all that instead.
(I picture a hallway with loads of receivers along them (All-most invisible screens of sort) That only display images or light while the headset is on (Inferred or something like that.) Then you can have the headset wirelessly attached to a computer of sorts that runs all the hard stuff to itself, and all the headset has to do is receive the images. (Might cause a small amount-ish of input lag.)

That's all for your post, Now the cost.

Okay. so.

A VERY basic grass area, Free i can make this myself.

a warehouse The cheapest AIRCRAFT hanger i could find was $120,000 for a large one, i think that was like for a week or something (Lazy Google search)

(ON THE NOTE OF THAT, It does NOT need to be a warehouse, It could be in a large open area too.)

3D model. Free, I can do this myself, Quite easily.
Oculus Rift I think the development kits for these are 300$ currently.
sensors for your hands fingers toes, Not sure as to what these cost. I would guess anywhere between 1-3000$ (and that's kinda pushing it)
wind device Large ass fan, No more then 180% (For one, We might need a few, IF outside, We could just use a wind reading device.)
A fake weapon Bahahahahahah 5$?

The cheapest it could be is about 3305$ and the most expensive would be 123,305$

(Not counting someone to come code the simple stuff such as movement tracking and ect.)

We could get someone who knows something about the Kinect (Xbox thing) And persuade (Torture) Them into using that as movement tracking instead of the suit.

So what I'm looking for, Is a headset you can put on ANYWHERE it'll do a scan of your surroundings, And make it look more fantastic.... (That's a bit of a leap though)

(There are NO spoilers, Its just to make it smaller.)

[spoiler]

This would be what i want SORT OF but instead of an anime character, More like the entire area (Oh i know! Ill use Clannad as an example!)

Without Goggles.(and setup)

With goggles(And setup)

(Source http://punynari.wordpress.com/2010/10/03/clannad-anime-pilgrimage/#more-5126)

[/Spoiler]

I might be thinking too far into the future, BUT if i manage to EVER even get close to producing this, I'll let you guys know. If its successful. Hopefully in the future it will be like Cloud Technology, All the processing is done in the cloud, You are tracked by something that I will come up with and the glasses display whatever you like. I don't know if this is happening everywhere, But in Australia someone is doing high speed free internet everywhere thing, (I heard about it on the news or something) Which could be wirelessly adapted for the headset.

If i can pull it off, (Which I seriously am going to try) i might innervate the future ^.^. As i said the hopes of it getting produced are stupidly impossible BUT I would personally love it if i could get it working, then give it to a developer to further exploit it. in-till it is accepted by the world.

Ill think of something For the time being i might just request to put depth cameras throughout a street. Get someone to program a 3D of the street world or ill just do a dodgy one then add some more awesome stuff to it.

(Off-topic)
In the FURTHER future, I expect that out body's will be redundant, and we will no longer use them to communicate with others. (This is thinking more along the lines of SAO again, But a full virtual world like Summer wars."I think that's what it was called")