Seeing Around Corners With Dual Photography

An anonymous reader writes "This project (which is part of this year's SIGGRAPH) has absolutely blown my mind. Basically they photograph an object with the photosensor at one point, and the light projector at another, and use the Helmholtz reciprocity algorithm to virtually switch the locations of the camera and projector, showing exactly what the light source "sees"! If that doesn't make sense to you, check out the research page and make sure to watch the 60MB video at the bottom. The playing card trick will leave you speechless!"

rays?

[dhbiker]

isn't this just the same in principle as ray tracing? or am I missing something

Re:Why don't the editors link to mirrordot?

[cortana]

They can edit the article once Mirrordot has completed mirroring. It does it so quickly that I assume it has a subscription and can take advantage of the subscriber-only period.

Re:A totally uninformed post!

[paulhar]

Finding the g-spot is quite easy. There is a great book that has pointers...

http://www.amazon.co.uk/exec/obidos/ASIN/189015902 6/qid=1115728290/sr=8-1/ref=sr_8_xs_ap_i1_xgl/026- 2537690-7222055 [amazon.co.uk]

Enjoy :-) [or should I say, let her enjoy?]

Re:Why don't the editors link to mirrordot?

[Anonymous Coward]

because not even Sanford can handle the traffic and now we cant even see the html never mind the video ?

not every server at sanford is sitting directly facing internet2 with load balancing server clusters and tb of ram, perhaps ?

mirror!

[jazzman75]

Someday soon, the owners of a site that gets slashdotted are going to sue faster than CmdrTaco can say "tort reform". It's irresponsible to post, unedited, an article suggesting readers download a 60mb movie without first making some effort to mirror/torrent the file and/or site.

Re:Why don't the editors link to mirrordot?

[Black Morning]

Even mirrordot got crushed... Seriously, what was the submiter thinking? Not to mention the editors.

The real question is why nobody made a torrent of this video before the story went live. Bittorrent is one of the posterchildren of open source and legit p2p, it's unfortunate that here on Slashdot, the center of the community, nobody ever bothers to use it for it's intended purpose. We have an opportunity to put a great FOSS project to a vitally needed user, but instead they choose to continue crushing servers. Sigh...

Blame The Slashdot Editors

[dohboy]

Don't blame their webserver/fileserver for not being able to see the movie they raved about.

It is the laziness and irresponsibility of the slashdot editors to not provide a bittorrent link.
I am disgusted that slashdot raves about a site/file/mpeg then DDOSs
it so that nobody sees it. This is particularly bad when a hobbyist site is crushed.

Mod me into oblivion, I don't care.

Re:Blame The Slashdot Editors

[Anonymous Coward]

mod parent up

Parlor tricks for the easily amused

[couch_warrior]

Gosh, how fascinating. Now compare this to a *really cool* imaging technique, like using an x-ray beam and an array of photodiodes to detect the scatter patterns as the beam passes through a human body, then calculate an image of the actual bones and organs inside. It's called Computed Axial Tomography or a CAT scan. And if you want something *realy really* cool, check out the technique that uses a magnetic field gradient to delay the re-emission of photons from an RF pulse, and then calculates the position of molecules in a body from their RF scinillations. Its called Magnetic Resonance Imaging or MRI. Somwhow I think the images they produce are slightly more profound that scanning the back of a playing card. Consider yourselves offcially Harumphed.

Re:slashdot, mirrordot, stupid: we need torrentdot

[MrDomino]

Forget that. This would be a perfect application for Dijjer [dijjer.org].

Re:Why use a camera?

[kevinank]

Rather than dual photography I would be more inclined to describe the method as real-world ray tracing. A focused pixel of light is captured for each pixel of the light source, then the scene is transformed so that the camera image is in the plane of the light source and the lighting function discovered earlier is inverted.

The article claims that there is no need to describe the geometry of the scene, and I understand why that is true for the structure of the subject, but it seems as though the geometry of the light and camera would still have to be known. Anything that isn't in view of the camera in the first image is unlit in the second image, and vice versa, but I don't understand how you would determine what transformation would result in that exchange without any information on the camera-light geometry in relation to the scene.

Re:Structured light.

[Bigman]

In fact, I can't see how this is a million miles away from what Logi Baird did with a Mechanical scanner, other than being more general.

Oh, comments above have to be interpreted in the light of the fact that I can't RTFA because of /.ing - !

Ian

Watching TV

[Doc Ruby]

To analyze the projector's image quickly, they need to control the projector, sampling its pixels' images to factor out redundant pixels. Trojan-horse programs which control the projector probably won't trigger current antivirus SW. Any screen can now spy on you, if a camera can only get a glimpse of its reflected light. Combined with laser microphones [mtmi.vu.lt], you're on candid camera! Beware untrusted screensavers!

Re:around corners?

[psyon1]

All they are doing is intensifying a reflection, that is not "seeing around corners." If they did the feat without the book present, then I would be impressed.

Re:A totally uninformed post!

[poot_rootbeer]

With this technology, any man can find the g-spot.

Unlikely -- you'd still need to get the light source in there somehow...

Re:Blame The Slashdot Editors

[LesPaul75]

I guess so, but I think the whole question of giving the site the hits that it "deserves" is bogus, because all those hits are coming from Slashdot users. In other words, the site wouldn't even get those hits if not for Slashdot. So if Slashdot chooses to cache the page for its own users, how can the owner of the site complain?

Besides, The traffic to the site will still increase, simply because the site will be getting free advertising on Slashdot. The story will fall off the Slashdot front page in a day or so, at which point people will go to the original site, if they're still interested. Even better, Slashdot could just destroy their cached version at that point.

Re:Blame The Slashdot Editors

[LesPaul75]

IE's caching is entirely different though: IE only caches a page when each user views it. An IE cached pages does not mask 10,000 other views.

But if IE didn't cache pages, sites would get several times as many hits as they do now. So it is a similar issue, but yes, it's a different type of caching.

But, Slashdot would also cache the advertisements, so every user who reads the story would still see those precious ads. And, assuming they do something similar to Mirrordot, the links would be unchanged from the original site. So if someone clicks on an ad in the cached version, they would still be taken to the advertiser's site.

The more correct analogy is this: You run a free newspaper that relies on advertising revenue. One day, the NYT sees an article in your crummy little paper that they like. They decide that they want to reprint your article. Hey, you were giving it away for free, anyway. So, they have two choices: 1) Grab every single copy of your free paper that they can find, or 2) Just buy one copy and then use their own massive printing presses to reproduce the article, along with all the ads on the page, giving full credit to your paper as being the original source of the article.

Option 1 just isn't feasable, because your presses can't supply enough papers, and more importantly, you (the free paper) don't gain anything from option 1, anyway. You could argue that the Internet is a different ballgame, because advertising revenue is based strictly on the number of hits to your site, but it's only that way because the advertisers have chosen to structure it that way. Caching is a painfully obvious way to improve the Internet, and it just makes sense. If advertisers can't find a way to adapt to it, well, they suck. Advertisers shouldn't restrict the advancement of technology just because it doesn't fit their model, especially when it's something that's such an obvious solution to such an obvious problem.