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Capturing 3D Surfaces Simply With a Flash Camera
Posted by
timothy
on Wed Aug 27, 2008 02:02 PM
from the more-depth-than-I've-got dept.
from the more-depth-than-I've-got dept.
MojoKid writes with this excerpt from Hot Hardware (linking to a video demonstration): "Creating 3D maps and worlds can be extremely labor intensive and time consuming. Also, the final result might not be all that accurate or realistic.
A new technique developed by scientists at The University of Manchester's School of Computer Science and Dolby Canada, however, might make capturing depth and textures for 3D surfaces as simple as shooting two pictures with a digital camera — one with flash and one without. First an image of a surface is captured without flash. The problem is that the different colors of a surface also reflect light differently, making it difficult to determine if the brightness difference is a function of depth or color.
By taking a second photo with flash, however, the accurate colors of all visible portions of the surface can be captured. The two captured images essentially become a reflectance map (albedo) and a depth map (height field)."
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Amateurs. (Score:5, Funny)
Bah! I completed my last project in exactly 6 days and used nothing but voice commands. It turned out so well I sat on my couch and ate Cheetos the entire next day. Today, there are over 6 billion users and we're only now starting to run into scalability issues.
-God
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Re:Amateurs. (Score:5, Funny)
Yeah, but look at how bloated your operating systemn is!
Parent
Re:Amateurs. (Score:5, Funny)
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There's a reason for that... (Score:4, Informative)
Obligatory XKCD [xkcd.com]
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Re:Amateurs. (Score:5, Funny)
Your project is a case study in bad management, though. Sure, you completed the whole thing in six days, but what are we left with? Documentation that's cryptic at best, and literally billions of bugs.
Parent
Re:Amateurs. (Score:5, Funny)
And don't get me started on that unhandled divide-by-zero exception!
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Re:Amateurs. (Score:5, Funny)
The divide-by-zero exception is hardly fair. How can he fix a bug that we can't even replicate? As soon as the LHC comes on-line, we can file an official bug report. Until then, let him off the hook.
Parent
Re:Amateurs. (Score:5, Funny)
He does at least seem to fix hacking vulnerabilities though. According to accounts there used to be a lot more magic about only a few centuries ago. Or maybe the talent just matured and moved over to the more challenging but reliable fileds of reverse engineering and repurpousing the apparrently intentional features.
If only similar attention was directed to safety...
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Re:Amateurs. (Score:4, Funny)
Gameplay sucks, just one endless grind.
Parent
Re:Amateurs. (Score:5, Funny)
Obviously, you haven't unlocked the right minigame. It's a short game, but it makes grinding fun.
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Oh, you make it sound so easy... (Score:5, Funny)
Unfortunately unlocking the minigame can be nearly impossible if you have the wrong arbitrarily-assigned game character. Of course you could modify your character and change your character's gear to make it a little easier, but that's even more work and expense and doesn't make a big difference. There's also a way to pay your way into one minigame session but you'll have to be discreet about it unless you want to start another minigame that involves a lot of not-fun stuff like carefully balancing a slippery bar of soap.
Parent
If you make enough simplifying assumptions... (Score:5, Interesting)
Quite old news (Score:5, Informative)
Slashdot (can't be bothered to find it) had a story several years ago about the (then old!) technique of capturing complicated 3D objects, such as car engines, by using two flash images, each with the flash located in slightly different locations. Threshholding the difference between the images gives very nice edge detection, along with very accurate depth information.
A project I'm working on uses the technique to capture information about arrowheads/spearheads.
Re:Quite old news (Score:5, Informative)
But this time the camera stays fixed and there is one without flash and the other with it. Allowing for 3D Cameras to be made on the cheap by just a firmware upgrade (one click of the camera takes 2 shots 1 without flash the next with. Your way is different as it requires the camera to have 2 flash thus needed the making of new cameras.
Parent
Re:Quite old news (Score:5, Informative)
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Warning: (Score:5, Funny)
TFA requires Flash.
A question for mojokid (Score:5, Insightful)
Why didn't you just link to the more informative New Scientist [newscientist.com] article that the blog you linked quoted?
Re:A question for mojokid (Score:5, Insightful)
Parent
Don't get too excited (Score:4, Informative)
This is just a way to automatically generate surface bump maps. It does not really capture depth information (like a Z-buffer).
Conceptually it seems simple enough (take a photo with shadows from a light source not in line with the camera, take another where all the shadows are in line with the camera (making them virtually invisible), tell the software which direction the light is coming from in the first photo, and let it figure out the relative height of each pixel, by analysing the difference between it and the uniform (flash-lit) version, after averaging the brightness of the two. It's similar to the technique some film scanners use to automatically remove scratches.
I can think of a lot of cases where it won't work at all (shiny objects, detached layers, photos with multiple "natural" light sources, photos with long shadows), but still, for stuff like rock or tree bark textures it should save a lot of time. As the video suggests, this should be very pretty useful for archaeologists.
Why a flash? (Score:4, Interesting)
Why not cameras that use different wavelengths of light, etc? For example, one that works in visible light, and one that works in infrared?
How about the use of different polarized lenses to block certain wavelengths of light?
The differences with having Flash in photos (Score:5, Funny)
"shooting two pictures with a digital camera -- one with flash and one without. "
This difference has already been well-expressed across the internet for years. [imageshack.us]
Re: (Score:3, Funny)
Re: (Score:3, Funny)
Primarily "Blinding Yourself with Science", with a minor in "Sound and Signal Processing".
Cheers
Re:Article has a minor gaffe (Score:4, Informative)
No, with flash (light source coming from the camera) shows the colors without shadows; i.e. without color perspective. Without flash (light source at an angle to the model/subject) shows the deeper parts in shadow (known to us former art students as "color perspective").
You could actually fo this with two flashes, provided one was on the camera and one to the side. The fact that it flashes has nothing to do with it, it has to do with the angle of the light sources.
Parent
Re:Hello, what about Victorian-era stereographs? (Score:5, Interesting)
Parallax and stereoscopy both require the camera to be in two (or ideally with parallax more) positions. The ingenious thing about this idea (watch the video, it's good) is that the camera doesn't need to be moved. By taking two shots in the same spot, one with flash and one without, you can get a good depth map.
Now it's not as good as a laser scanner, but it's much cheaper and faster and smaller (since you could use any little camera). It's a very simple but ingenious idea. I'm quite surprised by the amount of detail they are able to get this way.
Of course it could be argued that parallax and stereoscopy are ways of viewing images with pseudo-depth as opposed to taking them (at least for the purpose of this article). Parallax has no real depth, but helps simulate the effect in the brain. Stereoscopy has no depth, but works just like the eyes to give the brain the data it needs to reconstruct the depth.
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