dual projector passive 3d setup

Hi,
You are trying to watch content without having first tested whether ot not you mounted your filters correctly.

Circular polarisers only work one way, you might have mounted them backwards (in which case, they behave like linear filters), and they also have a primary orientation which need to match your glasses position. You need to rotate them until they are in their proper position, otherwise you'll get significant amounts of crosstalk.

You'll need to check all that by testing each filter individually by displaying a picture only in one eye and checking that the picture is correctly blocked i the other eye. You can use some crosstalk test images and videos, but since you're running on a computer there is a very easy way to create a crosstalk test just by using your windows desktop :

First change your desktop background image to a black background, then open a window (anything) only visible on one on the desktop (so that only one projector displays it). This is the most extreme crosstalk test you can do (fully white in one eye vs fully black in the other eye)

Put the glasses on and try the filters in front of the one projector that diplsplays that window. Try each filter individually and see how the window appears on screen. If it appears equally bright in both eyes, the filter is backwards. Then rotate the filter until the window is fully visible in one eye and as dark as possible in the other..
However even if positionned the right way, you will still get crosstalk because silverscreens don't keep 100% of the polarisation (especially when using circular posarisation).
Once you get it as best you can in one eye, move the window to the other deskop to do the other eye.

You use a passive system : 120Hz will not make or break the 3D effect. In fact it will work at any refresh rate (from 24Hz all the way up to 120Hz). You have probably been reading articles about active 3D which has nothing to do with your setup.
If you projector supports 120HZ, it will be a good thing for games : if you play old games that your computer can render super-fast, you will be able to run some of them all the way up to full 120 frames per second in both eyes which no other 3D display can do.
It won't change anything for movies though since the source is usually limited to 24 frames per second (bluray) or 30 frames per second (most videos on the web). There are some videos with higher framerates but they are very rare, and usually top at 60 frames per second. I have never seen anyone broadcasting 120fps video anywhere.

In your case, first we need to determine where the problem comes from to fix it.
Can you try to describe the problem a little bit better. What exactly do you mean when you say "the picture seems 2D, no 3D effect"

Do you see any difference in depth between various parts of the picture or is the picture all flat ?
Is there a technical problem ? do double images ruin the picture (too much crosstalk) or is the picture clear enough ? are the left and right eye view reversed (you can see the picture has many layers of depth but the 3D looks like garbage) ? is the movie player sending the left and right eye views to the correct projector or is the movie player sending the same eye view to both eyes ?

You can "read" the depth space by looking at the picture without glasses : you will see a double image but the spacing between the double images change depending on the depth of the object you are looking at. Stuff in far depth will have a strong double image with a large amount of parallax (with the right eye image located far on the right of the left eye image), stuff at the screen depth will have both images merged almost perfectly and look like 2D (no parallax), stuff coming towards you in pop-out will have a double image but crossed over (the right eye image located on the left of the left eye image). Can you see these differences or is everything at the same depth (everything has the same amount of separation) ?
Have you lined up your projector properly ? (clone your desktop and display a 2D picture so that both projector show the same thing) The projector alignment doesn't need to be absolutely perfect by the pixel, as long as you're within one or two pixels you should be ok. it's very hard to get perfect alignment, you just want to make sure your projectors aren't separated too widely which would offset the depth space. (you can also offset the pictures horizontally on purpose to force the picture to be more in depth or more in pop-out, however I do not recommend doing so)

Is it a movie problem ? The 3D effect will only be as good as the content your are displaying. What is the video you are using ? Is it a proper 3D movie or is it a crappy conversion ?
Not all 3D movies use the depth range in the same way : theme park movies have a strong 3D effect often : they often send stuff flying towards you and use huge depth ranges from far in the distance all the way up to a few inches in front of your nose to impress viewers. Feature length movies will use a much more moderate amount of depth and only send stuff in your face in extremely rare circumstances (the point of the movie is the story, not to use 3D as a gimmick. What does the picture look like without the glasses ?
Edited by BlackShark - 1/21/13 at 5:39pm