Seeing Around Corners With Dual Photography 381
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!"
Does it work for... (Score:2, Interesting)
around corners? (Score:2, Interesting)
Another application (Score:5, Interesting)
Other than using electrons instead of light, that's how a scanning electron microscope works. An object is scanned (raster scan) and one or more sensors near the target pick up the reflections to generate an image. In the SEM the image appears as viewed from the scanning electron beam source.
In the optical one mentioned in the article, the light source is a raster scanning projector which lights a target. The image is produced from photodiodes picking up reflected light.
These two systems are very much alike. One uses photons and the other electrons. The end image is generated the same way.
Military applications? (Score:5, Interesting)
It seems like this might have some military applications as a result. Imagine sticking a photo-resistor array under a door or through a window and then getting "viewpoints" from any of the lights in the room. Could aid in target aquisition and elimination.
Not sure how well it works for something like that, but this is a rather impressive (at least to me) research project.
You will never see around the corner, 'cause: (Score:3, Interesting)
2. You should know not only amplitude, but *phase* of the source signal, that means for light that you have to use coherent light source and utilize interference on the receiver.
1 + 2 = holography, so what is new?
(Read the article, but still downloading the movie)
Re:IANAS, but it looks like reverse 3d rendering.. (Score:2, Interesting)
Something like this?
http://www.cl.cam.ac.uk/~mgk25/emsec/optical-faq.
Voltara
CoralCache to the Rescue! (Score:2, Interesting)
Come on kids, coralcache is the way to go. no more direct linking to servers that go down quicker than, well, you know.
Re:Why don't the editors link to mirrordot? (Score:3, Interesting)
I don't see any reason a torrent client can't be set up to allow a HTTP seed in addition to all the torrent peers and seeds. Granted it's going to get very poor speed, but as soon as a chunk makes it out into the swarm it should disperse to everyone fairly rapidly, and the more automated it is, the sooner there will be other seeds to take over.
You would still need a database somewhere to provide a URL to torrent mapping, but perhaps something like the new distributed DB in the most recent Azureus would be flexible enough to encompass the task.
Once you have those two pieces in place, it's as simple as reassociating browser links to
Re:Why don't they just move the camera? (Score:3, Interesting)
Re:Why don't they just move the camera? (Score:5, Interesting)
How much information can you gather from that reflected light?
You could of course recinstruct the image on the CRT, but that's not very interesting.
The TV does not scan a focused image on its surroundings like the projector does, so you couldn't get a TVs-eye view of the room witht eh same technique.
OTOH, it is clear that from sampling even just a single point on the wall, you could get a silhouette of anything occlusion over the screen seen from that point. At least provided you had a pure white image on the CRT, OR knew what image was on and could calibrate for it.
How far could you get with all the information escaping the window in your direction?
what if you had dozens of eyes? (Score:3, Interesting)
Applications of these arrays included several kinds of real-time 3D TV (without silly glasses). The Stanford group pushed "conformal imaging", that is a cube of image planes at various depths and all viewpoints. This has the effect of looking around corners and through keyholes: if there a path for light to get through, you can probably extract a complete image. This does involve some mathematical massaging of multiple-camera images. Cheap Graphical Processing Units (GPU) from game machines can be reprogrammed to process images in real-time.
Re:It's all very impressive, but.. (Score:3, Interesting)
Re:Blame The Slashdot Editors (Score:3, Interesting)
Who would imagine that we could
Oh well, I guess the Graphics department at Stanford isn't recieving any love from their IT department.
Re:It's all very impressive, but.. (Score:3, Interesting)
But there are two catches: (1) when you see a point in the scene it might not be along the ray you expect from the projector because it might be due to a reflection and (2) it's expensive to rasterize each point individually so instead you use a binary coding scheme to you only have to project log(N) images, where N is the number of pixels. Dealing with these issues successfully is very cool - but fundamentally the original poster is giving a 100% correct description. This talk of "Helmholtz Reciprocity" gives the misleading impression that something deeper is going on. "Helmholtz Reciprocity" is why ray-tracing works, ie. why you can send rays 'backwards' from the camera into the scene to generate a CG image, it's not some deep new principle.
Re:Blame The Slashdot Editors (Score:3, Interesting)
By the way, one of the guys, Levoy, is awesome. He did all that digital modelling of the statue of David stuff.
Re:Blame The Slashdot Editors (Score:3, Interesting)
NEWS FLASH: The only people who will be viewing the cached version are... wait for it... Slashdot users! That's right! And more importantly, you don't generate a lot of advertisement revenue when your site is offline due to the Slashdot effect.
So the Slashdot editors' argument (here [slashdot.org]) basically boils down to this:
Private: Sir, we've accidentally launched a nuke that's headed for downtown Maimi.
General: Boy, that sucks for Miami.
Private: Well, sir, we've got twenty minutes before the detonation -- shouldn't we at least sound some sirens or something and at least give them a chance to evacuate?
General: Sure, I know that evacuation sounds like a great idea, but think about it -- you'd be depriving all those people of their right to see the beautiful mushroom cloud that forms. And anyway, lots of people will probably survive the explosion. Only the unfortunate (half million or so) people who live right in the downtown area and don't have proper nuclear-bomb-proof apartment buildings will actually die. I mean, hey, maybe we could try to just evacuate those unfortunate few, but do we really want to go to all that trouble? In the end, private, evacuating Miami is "a complicated issue that would need to be thought through in great detail before being implemented."
Private: Excellent point, sir. Poor bastards.