With any 3D system you only need to replicate the viewing ability of a human being. Which means only what you can see from the fixed point of each eye moving around.
This is basically the principle behind immersive virtual reality systems. The usual system uses a motion tracker with the reciever (a small cube) attached to one side of the 3D glasses. The system then knows the location of each eye. It then simply renders each eye’s view. You can walk around, and the view remains correct. This allows some great effects. If you model a nice molecule you can stick your head inside the molecule - and it still works. However most systems can only render the view of one person. (There were two person systems made - but the 3D glasses had to be modified and the video projection systems were run at the bleeding edge of their capability.) A system that rear projected 3 walls and the floor ws enough to produce a very compelling immersive experience. However there are insurmountable problems too. The brains stereopsis mechanism would report a perceived distance based upon the geometry of the view. However the focussing distance remains the distance to the screen. Thus the eyes would report a potentially significantly different distance to the object. This, and other issues, is enough to give anyone a headache after about an hour’s use.
One could make a 3D system by using 3D pixels if you had materials that were perfectly transparent with no/an electric signal and either matte black or glowed red, blue, or green with an/no electric signal. You’d end up with a computer monitor the size of an old CRT monitor and you’d have something like a cubical space to fill. You would probably also want to angle the alignment of the pixels to be forward-facing to a particular POV for best results.
3D pixels from overhead:
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| Black | Black |
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| R | G | B | R | G | B |
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| Black | Black |
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| R | G | B | R | G | B |
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^ Facing front
So far as I’m aware, no one is working on such technology. Possibly its open for patent (until just now). 
Another idea along the lines of a transparent cube of pixels would be to a transparent cube and create glowing dots inside of it by intersecting several lasers at that point.
That doesn’t allow you to create a black/light-blocking region. Lowering the brightness of an area, in your version, would be equivalent to raising its transparency. If you wanted to create a black square, for example, it would be almost entirely transparent. If you detected where the viewer was, you could dim everything behind the black square to also be dim, but that becomes very complex and would only allow a single user to view the device. You would also have the problem of a general haze of light due to the millions of laser beams scattered all about the general region. Point in fact, I’m not sure that having three lasers focussed on the same region would make the point of collision all that more visible unless you had (for example) a very small reflector at that point in space.
I was envisioning something more along the lines of a special material that the cube was made of, along the lines of a transparent LCD (or even maybe 3D CRT phosphors) but without any electronics running to the pixels, using lasers for both back-lighting through some form of scattering and pixel activation.
I recently read they’re releasing the next generation of 3D TVs in Japan soon, but 3D TVs have been available for a while now. One local shopping center has 3D TVs placed throughout, playing commercials on them. And they look absolutely horrible! Gives me a headache just looking at them.
The Princess Leia “help me Obi Wan” type of hologram is possible today. The problem is it’s not floating in the air but contained inside some kind of device.
It’s still pretty cool, though. Does anyone know how this works?
Channel 9 are broadcasting The Rugby League State of Origin series in 3D in the next few weeks. All the commentators that I have heard discussing it say the trial broadcasts are like being out on the field.
Can you give me an example that would actually be more likely to occur? Because I’m having a lot of problems coming up with anything.
Anyways, since pretty much all film seems to go through some sort of digital processing these days, I’m not sure that information couldn’t be added back in post.
Also, remember, you’re not going to be able to look at a 3D television from any angle. Think of it as looking out a window. There’s only a certain range in which you can see anything, and any angle other than dead on is going to have a smaller viewing area.
I think the idea that this would take an infinite number of cameras is silly. Maybe more than four would be optimal for concavities, but if it were infinite, 3D scanners would be impossible.
OK, someone wearing very elaborate clothing with a lot of pleats, folds, fur, or other protrusions. With a small amount of cameras, you’re likely to end up with some spots that are “shadowed” from all of the cameras. Admittedly, most objects are simple enough that you’ll get a pretty good view with four cameras, but not always for every point.
3-D scanners do exist, but for complicated objects, they take some skill to use, because you have to know to position the object correctly to get all the information, and it does typically take many angles.
acetylene, it’s hard to say how those trade show “holograms” work. At least some of them might be true holograms, but some others clearly are not. The ones that show a single object rotating could be accomplished by simply rotating the film, but we don’t yet have the technology for smooth animation like the little dancing guy, so that must be some other sort of trick.
Oh, and on the crossed-lasers idea, there are some materials which will absorb two photons of low-frequency light, and then emit a single photon of high-frequency light. If you make the low-frequency lasers infrared, then you wouldn’t be able to see the beams themselves, and since it requires two photons to hit the same atom in rapid succession, the intensity of light emitted is nonlinear with the intensity of the original beams, which would help alleviate the ghosting problem. I think it would probably work, theoretically at least, but you’d probably need a lot of technological development to make it a reality, and I’ve never heard of anyone even working on it.