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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!"
The exploding server one has already rendered me speechless. Why in the name of god do they do it!
..it would be much easier.
Mirrordot link to the video file.
I find it highly unlikely that many will manage that :0
Brocklesby Park Cricket Club
Anyone please mirror the movie?
J.
You're only jealous cos the little penguins are talking to me.
Dual Photography
Abstract
We present a novel photographic technique called dual photography, which exploits Helmholtz reciprocity to interchange the lights and cameras in a scene. With a video projector providing structured illumination, reciprocity permits us to generate pictures from the viewpoint of the projector, even though no camera was present at that location. The technique is completely image-based, requiring no knowledge of scene geometry or surface properties, and by its nature automatically includes all transport paths, including shadows, interreflections and caustics. In its simplest form, the technique can be used to take photographs without a camera; we demonstrate this by capturing a photograph using a projector and a photo-resistor. If the photo-resistor is replaced by a camera, we can produce a 4D dataset that allows for relighting with 2D incident illumination. Using an array of cameras we can produce a 6D slice of the 8D reflectance field that allows for relighting with arbitrary light fields. Since an array of cameras can operate in parallel without interference, whereas an array of light sources cannot, dual photography is fundamentally a more efficient way to capture such a 6D dataset than a system based on multiple projectors and one camera. As an example, we show how dual photography can be used to capture and relight scenes.
(a) Conventional photograph of a scene, illuminated by a projector with all its pixels turned on. (b) After measuring the light transport between the projector and the camera using structured illumination, our technique is able to synthesize a photorealistic image from the point of view of the projector. This image has the resolution of the projector and is illuminated by a light source at the position of the camera. The technique can capture subtle illumination effects such as caustics and self-shadowing. Note, for example, how the glass bottle in the primal image (a) appears as the caustic in the dual image (b) and vice-versa. Because we have determined the complete light transport between the projector and camera, it is easy to relight the dual image using a synthetic light source (c) or a light modified by a matte captured later by the same camera (d).
Seeing that R-ing the F-ing A is an impossibility for me right now, due to an inexcuseable lack of .torrent or google cache link, I'll just post some outright fabrications about it's content.
This technology proves that there was a third gunman on the grassy knoll. This technique is like what they did in the Matrix, except "backwards." With this technology, any man can find the g-spot. When you look at the videos upside down, you can see into the past.
Doesn't it seem a little funny that we need a mirror to get a look at this movie?
The little guy just ain't getting it, is he?
DARN, /. just hiked Stanford's tuition rates again.
Bacardi + slashdot = negative karma.
Seeing around corners is really stretching it. You switch positions with the light source, so you can technically look at the scene from a point which is "around a corner". What they so casually mention as "structured lighting" is really the key to the whole algorithm and means that the light source shines a pattern on the scene which then allows the camera to retrace where every bit of light it sees is coming from. This means that the light source needs to be part of the scheme. You won't be able to switch yourself into the position of arbitrary lights on the street.
With a video projector providing structured illumination, reciprocity permits us to generate pictures from the viewpoint of the projector, even though no camera was present at that location.
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.
The truth shall set you free!
Note: I haven't read the paper yet, but it is downloading.
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.
There are only 10 kinds of people in this world... those who understand binary and those who don't
They make the point that if you illuminate an object with a projector, you can get the image with a photocell. That's because the projector scans the image with a light beam. If you know when you see the reflection, you know where the light beam was when it reflected because you have prior knowledge of the scanning pattern. That technique has been used forever. It's like the flying spot scanners that predate camera tubes.
The 3D part is obtained when you offset the detector and the projector. If I look at a particular point on an object and scan the object with a beam of light, I can get the distance between me and the object as a function of the scanning angle.
All these people are doing, are using the first barcode technique to, take a picture of the scene. Instead of using a laser, an animation of a moving white dot is sent to the projector. The Camera, is then treated like a light sensor, for each point in the animation, the camera is queried for the brightness of the perhaps, brightest dot in it's field of view. Gradually the picture is built up, pixel by pixel, untill, finally a picture is formed in memory. This picture would be from the perspective of the projector.
Maybe we could use that mirror to get a different viewpoint of the article?
Well, I've begun the download for this video, and seeing as how mirrordot is being slashdotted, I have only downloaded about 20 megs out of the 60 meg file, with an ETA of about 25 minutes. At any rate, I've put the mirror up linking to the file that's being created -- and in 25 minutes that file will be complete, until then it'll be some percentage of the total.
Enjoy.
If you mean in the sense that POV-Ray does, then no, this is very different. It's an "image-based" rendering technique, which means that you create new images using photographs and other such real-world measurements as input. Conventional ray tracing gives you pictures of models built in the computer's memory, which might approximate a real-world object.
The important difference is that you don't have to build a computer model of the geometry you're trying to render. This is both a help because many real-world objects are hard to model accurately in a computer, and a hindrance because you can only render pictures of objects that you actually have in the real world.
Only the first part for now :
a rt1.mp4.torrent
http://dload.digitalriviera.com/DualPhotography-p
Second part in 30 minutes !
First torrent I host, I hope it's ok.
Was I the only one that saw that as:
Seeing Around Corners With Dual Pornography.
I need more coffee.
Well, there's spam egg sausage and spam, that's not got much spam in it.
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.
1. Reverse transformation for any interesting case (note that no places are actually revealed on their example!) will always be close to singular, that means in practice that your noises (due to raster, finite precision, and just measurement error) will eat any signal in result.
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)
Another mirror here. No guarantees as to how long it will stay up; if it pushes me close to my monthly bandwidth limit I'll kill it...
BitTorrent file here. http://bisqwit.iki.fi/torrents/DualPhotography.mp4 .torrent
Could I image my hot neighbour's bedroom and see her make out in her bed from the perspective of her bedroom's ceiling light ? That would be killer ;)
No, that would be stalker. Still pretty bad, but not quite up to murder.
sudo ergo sum
Half truth:
If you watch the video, the very last demonstration is that of them generating the image of a King (of hearts?) that was not directly visible to the camera. Rather, its face was reflected onto the page of an open book - much more complicated that just, say, a mirror. The cards reflection is not visible in the still image of the book and is only made possible through pixel scanning with the projector.
In sum, they are seeing around a corner and are seeing something the camera could not see (directly).
-dave
http://millionnumbers.com/ - own the number of your dreams
http://ftp.acc.umu.se/mirror/media/DualPhotography /DualPhotography.mp4
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.
LibBT: BitTorrent for C - small - fast - clean (Now Versio
Nah, they do this every week on ,b>CSI
Cthulhu Barata Nikto