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The Nonphotorealistic Camera
An anonymous reader writes "This article on Photo.Net describes a new type of imaging technique that finds depth discontinuities in real-world scenes with multiple flashes added to ordinary digital cameras. As depth discontinuities correspond to real 3D object boundaries, the resulting images look like line drawings. The same technique was used at this year's SIGGRAPH to create a live A-ha 'Take On Me' demo."
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You are mistaken. The final image is the 'equivalent' photoshop filter, and it's showing what a poor job it does in contrast to the third image, a good image, from the multiflash.
3D cameras do exist ... though the one that I saw was a fairly substantial beast. About the size of a phone booth, you stand in the middle and well-calibrated cameras all around you take pictures, generating a 3D model of whatever's in there.
It was strange seeing a surprisingly high resolution 3D model of me on screen seconds after I'd stepped out of the thing.
The depth edge maps bear a superficial resemblance to phase congruency maps. It's the best edge detection method I've come across, and works on ordinary 2D images. Check out some examples on Peter Kovesi's pages, there's also some code for download.
Escher was the first MC and Giger invented the HR department.
3D analysis requires stereo-pair of images, like this. Alternative would be to use some kind of radar or sonar, measuring time-differences of bounced signals, etc. Those and other methods for 3d digitizing.
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What should work too, is using two camcorders taped together. Stereo photography has been around for ages.
Yes, but the whole point of this system is to use one camera which is much cheaper and simpler to implement than two.
Additionally, if you RTA, it is mentioned that this system copes better with surfaces which would look uniform (white object on white background) than a stereo-based system, as different directions of light are more likely to expose object borders than light from a single direction.
.: Max Romantschuk
I've seen something similar to this being done before by sending out very short but wide-angle pulses from a laser. By capturing an image with a high speed camera, only a thin slice (in the z-axis) of your scene will be illuminated at any time. By adjusting the timing between the pulse and the shutter, you will be able to control how far away the laser blink gets, and thus you will be able to create a continuous depth-map of the scene.
- jeps
Isn't this how the coloured-glasses 3D filming that was briefly popular in the mid 80s worked?
Doubtful. All you need to make a red-blue 3D movie is two cameras a certain distance apart. Apply a red filter to one and a blue filter to the other, and voila. This multiple-flash technique uses a single camera, as would the parent's suggestion.
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For those that are uneducated in graphics, the engine photos show two comparative methods:
The TOP row shows how the camera output is good enough to be used as a technical drawing- it requires very little modification or touch-up.
The BOTTOM row shows how a Photoshop filters butcher the image and the result is completely useless. No amount of touch up could help that image.
Furthermore... NO THIS CAMERA CANNOT BE USED ON MONOCHROME IMAGES. It can't be used on any kind of images, and it isn't a post-filter. There isn't any edge detection involved.
The 4 flashes cause shadows to be cast in 4 different directions and creates a composite from the difference. If the subject DOESN'T cast a shadow, then the camera won't work.
I assume this camera cannot be used to photograph the outdoor scenes, simply because the flashes will not render shadows at that great distance.
This is an brilliant method though, and the results are excellent (look at how the details in the spine pop out).
FYI, they're called "View-Master," and apparently they're no longer available in the vertical-wheel red/orange style I had as a kid.
Pfft. Red eye? That's two flashes. With four flashes, you need to run the forked tail and horn remover, too.
Well, technically, red eye is avoided with two flashes. One flash surprises the eye and reflects light off it before the pupil has a chance to shrink. Red-eye removal basically takes a "pre-flash" to prepare onlookers for the real picture.
Joking aside, this 4 flash thing does make me think that it's not useable on any targets that are moving at all.
If you want a 3D model, then this isn't going to be a big help to you. But oftentimes you don't need a full model, you just need a really good image from one or two POVs.
In my previous life in manufacturing, this would have been a godsend for creating as-built drawings of custom work and for making assembly drawings for the customer.
For its designed purpose, this is brilliant.
With reasonable men I will reason; with humane men I will plead; but to tyrants I will give no quarter. -- William Lloyd
That's where Photoshop comes in. It seems like most of the math tools required are built in as layer modes...
From the article:OK, this is stacking your 4 images as layers in Photoshop with the Mode of each layer set to "Lighten". Once you've got your shadow-free image,
To be acurate, you'd probably want to have your 4 strobes on stands and measure their distance from the lens to ensure equality. Looks like the advantage of what they're proposing is having it all in one box. But as you mention, the poor man's method should be just as effective.
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Glasgow uni, Scotland, where I study.
And yes, it's pretty damn cool to see. They have lots of computer graphics/computer vision stuff going on here, some of it's pretty funky.
That's some pretty impressive edge detection, thanks for pointing it out. A related problem is to identify areas in an image that are the same thing. The best algorithm I know of for segmenting images is Leo Grady's brand new iso parametric graph partitioning method. His work is at http://cns.bu.edu/~lgrady/. His PhD thesis is probably the best place to start.