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140" Monitor Demonstration At Purdue
michaelpapet.com writes "Edward J. Delp, a researcher at Purdue University is working with Philips to make a monster 140" monitor using 4 projectors on a single screen. Article claims it would be good for National Security... I dunno, I see this being the only way to satisfy 'big screen envy.'"
It's a projection screen. You could always make those as big as you want based on pure optics.
However, that's not the tech advance anyway. What they're really showing off is the way to get multiple projectors to work together so that you end up with four times the projection area and also four times the resolution while using relatively off-the-shelf projectors, and avoiding the seam effect that would happen if you tried to do this yourself.
I'd hardly call this "innovative" or even label it as a "technology." It's a standard multi-image slide show trick that probably goes back at least to the 1960s. (It was old hat when I did it in 1989.) It has been done with movie projection and is routinely done with video projection (see Dataton WatchOut).
The trick is to have some overlap between the projection areas, and to use complementary gradient filters at the overlapping edges. The gradient filters can hide seams that even the slightest misalignment would cause.
There was a graduate student (at CMU?) who made a nifty program that could compensate for alignment problems. The projectors could be crudely aligned, then grids were displayed on each one. A PC cam captured the grids, computed the offset, tilt, and keystoning. From that information a reverse transform was applied to each projector's output, and you got a remarkably well aligned multi-projector image. Very impressive, since the cam was obviously much lower in resolution than the composite image.
Multi-projector techniques are even more important with video than they were with slides, since the light output of video projectors is so much lower. To throw a big image, combining multiple projectors is the most practical option.
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I'm a little late to this thread but this is definately not news...two years ago I was working for PPPL (www.pppl.gov) and we had 12 projectors tiled together to form one large display. Princeton U. main campus had 24 I believe. I've also worked on the Rutgers U. Engineering has one that tiles 9 together.
:-)
Here's how it works. The RU and the PPPL walls were powered by a linux cluster, one machine per projector with a high end graphics card in it (Yes I played Unreal Tournament on it...it was damn nice). How does Unreal work on it? At the time we were using a project called WireGL which intercepts OpenGL calls on the master machine (or whatever machine is running the program) then splits them up across the Myrinet network to the machine that will render the image on it's section of projector. This project was run out of Standford while the new version of the project is called Chromium is now located out of UVA. This projects also not only split up the image but allow for pixal overlap so that the image appears "seamless".
Yes I've also seen parts of the Matrix on the PPPL wall as a coworkers project was to write a parrallel MPG player for use on the wall, as this was a summer fellowship project he did not have much time to complete it and took a basic approach to it which was preprocess the mpg to split it into the configuration then using a modified mplayer I believe it was added networking code to syncronize the images, sound was not completed during the summer.
Princeton U's cluster was a windows cluster which needed custom video drivers to power their wall but otherwise it was the same principal (when I left Princeton U was supposed to be moving the cluster over to linux).
From skimming the questions in this thread I believe I've answer all but the DPI question...and that ends up being you do not have a pixalated display, infact at PPPL before we scaled up to 12 projects (the number of them when I left there atleast) the wall was a 7 Megapixal display and we found images taken with a 7 megapixal camara...they look simple stunning, in one image you were able to see finishing nails driven into a table cloth to keep it down.
Anyway I hope that answers everyone's technical questions.
Cheers