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Dual-Projector Polarization

Build Your Own: Wall-Sized 3D Gaming, Just Like Theaters Do It
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Dual-projector polarized displays are used in most 3D theaters. IMAX 3D, RealD, and Dolby 3D all use a variation of this 3D display technology (there are some technical differences but for the sake of simplicity we won't go into those details here). The method is somewhat simple and elegant when compared to alternate-frame sequencing. There is no mechanical trickery required to cover one of the viewer's eyes at a time or technology needed to sit on the viewer's head in the form of expensive LCD glasses. You do need passive polarized glasses, but the cost is insignificant compared to LCD shutter glasses. Not coincidentally, this is why the method is so prevalent in theaters where patrons might accidentally damage the equipment.

This technology makes use of the polarization of light, a relatively old and commonly-used technique implemented in garden-variety sunglasses. A dual-projector polarized theater relies on two projectors to deliver video to the screen, with each projector delivering a unique perspective for a specific eye. Each projector lens is attached to its own polarized filter. The viewer has to wear glasses, but the glasses contain no electronic parts. Instead, the glasses simply employ passive polarized filters. The filter over the right eye will block out the polarized video that is intended for the left eye, and the filter over the left eye will block out the polarized video intended for the right eye. This way, each eye only sees its intended perspective, even though both perspectives are displayed on the same screen.

Dual-projector polarization is used not only in theaters, but also in some specialty monitors designed for the PC. When used in a monitor, a polarized filter is located directly on top of the monitor's screen. Two examples of this are the iZ3D and Zalman 3D monitors.

What are the advantages of dual-projector polarization? Its most significant benefit is that it is easy on the eyes, regardless of the refresh rate of the projectors. Because no active LCD shutter glasses are strobing the light that gets to the eye, it is comfortable to watch this method of stereoscopic 3D with a pair of 60 Hz projectors.

The second advantage is that polarized glasses can be purchased for less than a dollar a pair. Want to invite 20 people over for a 3D party? Less than $20 worth of glasses will take care of it.

What's the downside? The up-front costs are much greater. A dual-projector system requires two projectors, which is a significant expense. On top of that, you'll need a polarized-compatible screen and polarized filters for each of the projectors. While this might seem like a lot, keep in mind that 720p projectors can be had for under $1,000, meaning the total cost of this setup can be kept well under $3,000 with little effort. The cost is comparable to a single 46" 3D-ready TV, which will require at least one pair of expensive glasses to operate.

What are the disadvantages to a polarized setup? First, crosstalk can be an issue with dark scenes. The polarized filters are never 100% perfect at blocking all of the light from one of the projectors, so if there is a dark scene and a bright object, some light on the edge of the bright object might be seen with the wrong eye. But if it doesn't bother you in the theater, then it probably won't bother you at home. Still, the drawback is something to consider.

Example of crosstalk--notice some leaves can be seen through the gunExample of crosstalk--notice some leaves can be seen through the gun

Another slight disadvantage is that the filters polarize the light across a plane, so the more you tilt your head, the more crosstalk you will see. Once again, this isn't a problem for most people, since they don't watch the big screen with their heads tilted sideways, but it's something else to keep in mind.

Perhaps the most notable disadvantage of the polarized method is that it remains questionable whether or not 3D Blu-ray discs will ever be compatible. No one has yet announced a dual-projector 3D Blu-ray software player. CyberLink's PowerDVD 10 looks like it might be one of the only games in town when it comes to 3D Blu-ray playback on the PC, and the company has indicated that dual-projection setups will not be supported. It intends to rely mostly on alternate-frame sequencing for 3D Blu-ray playback, although it will support a number of other display options.

In any case, this article is about recreating a dual-projector polarized 3D setup in the home. Just because we can't playback 3D Blu-ray discs with this method yet doesn't mean we can't play games in wall-shattering awesomeness and it doesn't mean we can't watch movies in 3D, either. Even though we've made clear our intention to create a dual-projector polarized 3D theater, there's still a lot more ground to cover when it comes to a wall-sized 3D display in the home, and specifically on a home-theater PC. The key is the software.

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Top Comments
  • 26 Hide
    MiamiU , March 30, 2010 6:32 AM
    seems like being a hardcore gamer just keeps getting more and more expensive...
  • 23 Hide
    Icehearted , March 30, 2010 6:56 AM
    As for poor folk like me, we'll just settle for those still images where we cross our eyes, and cry because $2,565 is far away from "comfortable".
  • 12 Hide
    salgado18 , March 30, 2010 1:11 PM
    I don't know if it would be possible, but it would sure be AWESOME to see some of those games on a short gif animation in "fake" 3D! Please! (a video review would be great too!) :D 

    PLEASE people, vote me up! If you do they'll try it!
Other Comments
  • 26 Hide
    MiamiU , March 30, 2010 6:32 AM
    seems like being a hardcore gamer just keeps getting more and more expensive...
  • 23 Hide
    Icehearted , March 30, 2010 6:56 AM
    As for poor folk like me, we'll just settle for those still images where we cross our eyes, and cry because $2,565 is far away from "comfortable".
  • -3 Hide
    winner4455 , March 30, 2010 7:29 AM
    I can see this becoming main stream and the next few years... In 3d too.
  • 6 Hide
    tigerwraith , March 30, 2010 7:59 AM
    2.6k now but you know things like this keep getting cheaper and cheaper. Maybe by this time next year, the 1080p 2600 lumens will drop to 500, and the drivers will better support dual projector setups.
  • -4 Hide
    tigerwraith , March 30, 2010 8:09 AM
    But I do have a question would of mattered if you used LCD projectors?
  • 0 Hide
    gti88 , March 30, 2010 9:40 AM
    Great article! Thanx a lot.
    But as I can see, 3D stereo is not there yet.
    Almost no movies are available at 3DS, and game developers don't focus on stereo optimisation. Thus, we have some glitches and inconveniences.
  • 1 Hide
    pojih , March 30, 2010 9:59 AM
    ahh, something else to cost an arm and a leg...

    not saying that many people here don't want the fastest and most expensive....

    but it was clearly shown that many people looking at this site want something that performs for what it costs, as seen by the fermi release and the comments .....
  • 2 Hide
    skora , March 30, 2010 10:24 AM
    Whats the next price bracket up for a projector with higher res?

    I like the idea of dual projectors better than the alt-image standard, but they didn't ask me.

    Here's a wild thought, soon, everyone will have their own glasses that not only do the shutter for 3D, but will also be able to be personal monitors. Connect to any computer/phone/TV with your glasses. Displays might even become unnecessary. That will be the next wireless mainstream device. The iShades. Phone, mobile pc and display, earbud is right there. Have pants that have built in keyboard. We'll all just be sitting there with our shades on and never see the person next to us as we get lost in the cloud. And it all starts with 3D glasses. :p 
  • -1 Hide
    djab , March 30, 2010 10:31 AM
    IceheartedAs for poor folk like me, we'll just settle for those still images where we cross our eyes, and cry because $2,565 is far away from "comfortable".


    No, you can at least use red/cyan paper glasses with iz3d drivers and a normal display.
    That is not that bad!
  • 0 Hide
    manitoublack , March 30, 2010 11:05 AM
    Great article, and no doubt people ask you: "why have you got 2 projectors?" The only trouble with polarized setups is that you cant view 3D laying down, eg: Lounge Lizard style, which you can do with shutter glasses (however uncomfortable that may be.)

    Still though, for $2,500USD you've built a pretty mad setup. To those winging about price, deal with it, if you want the best you've got to be prepared to buy the best. I'd suspect that a WUXGA setup would be in the $5-6,000 range using the projectors you'd want. Well worth the buy-in price. I hope for your sake (if you payed for it, not Tomshardware) that it is compatible with yet-to-be-released BR3D.

  • 0 Hide
    mjello , March 30, 2010 11:17 AM
    manitoublackGreat article, and no doubt people ask you: "why have you got 2 projectors?" The only trouble with polarized setups is that you cant view 3D laying down, eg: Lounge Lizard style, which you can do with shutter glasses (however uncomfortable that may be.)Still though, for $2,500USD you've built a pretty mad setup. To those winging about price, deal with it, if you want the best you've got to be prepared to buy the best. I'd suspect that a WUXGA setup would be in the $5-6,000 range using the projectors you'd want. Well worth the buy-in price. I hope for your sake (if you payed for it, not Tomshardware) that it is compatible with yet-to-be-released BR3D.


    Samsung display dont work lying down
  • -4 Hide
    idisarmu , March 30, 2010 11:27 AM
    What's wrong with the old school red-green glasses? It seems like a much cheaper and convenient solution. I would hate having to recharge glasses, let alone wear them if they're going to be heavier than normal.
  • -4 Hide
    d70guy , March 30, 2010 11:27 AM
    There are a lot of issues with this. The lack of resolution, difference in brightness of the images over time (no two bulbs are identical), the less than ideal projection surface, the fact that all bluray titles will be 1080p for each eye, etc.. I mean, this *is* a fun toy, but not for a serious gamer, and not for an even semi-serious home theater person. It is strictly for someone with the money to blow on a toy.
  • 0 Hide
    d70guy , March 30, 2010 11:34 AM
    idisarmuWhat's wrong with the old school red-green glasses? It seems like a much cheaper and convenient solution. I would hate having to recharge glasses, let alone wear them if they're going to be heavier than normal.


    Red blue glasses are the worst case 3D experience. Both polarized and shutter glasses are 10 times better at delivering a realistic 3D experience. The anaglyph (red/blue separation of the image distorts the color of the image, and even with high quality (eyeglass quality) red/blue glass lenses the overall effect is that of a poor quality experience. Shutter glasses these days are not that heavy, and its not like you are going to be wearing them for the length of the movie. It really doesn't factor in. Personally, I will take the shutter glasses. They block light much better thereby eliminating the ghosting issues associated with the polarized lenses. I say this as someone who has worked with linear, circular, and shutter technology since the late 1980s.
  • 1 Hide
    Artman256 , March 30, 2010 12:21 PM
    From the dual projector page - "the filters polarize the light across a plane". This is not entirely true, old systems did that, but modern systems use circular polarization, which avoids the problems caused by tilting your head.
  • 1 Hide
    JohnnyLucky , March 30, 2010 12:21 PM
    This is going to be very expensive.
  • 12 Hide
    salgado18 , March 30, 2010 1:11 PM
    I don't know if it would be possible, but it would sure be AWESOME to see some of those games on a short gif animation in "fake" 3D! Please! (a video review would be great too!) :D 

    PLEASE people, vote me up! If you do they'll try it!
  • 5 Hide
    pluripotent , March 30, 2010 1:23 PM
    But Don! I'z only gotz one eye!
  • 2 Hide
    Rehnquist- , March 30, 2010 1:53 PM
    Why on earth are all the screenshots scaled down to such a low resolution?
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