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introStructured Light 3D Scanning
The same technique used for Thom's face in the Radiohead "House of
Cards" video. I'll walk you through setting up your projector and
camera, and capturing images that can be decoded into a 3D point
cloud using a Processing application.
House of Cards Google Code project
I've included a lot of discussion about how to make this technique work, and the general theory behind it. The basic idea is:
1 Download ThreePhase
2 Rotate a projector clockwise to "portrait"
3 Project the included images in /patterns, taking a picture of each
4 Resize the photos and replace the example images in /img with them
Point Clouds with Depth of Field from Kyle McDonald on Vimeo.
House of Cards Google Code project
I've included a lot of discussion about how to make this technique work, and the general theory behind it. The basic idea is:
1 Download ThreePhase
2 Rotate a projector clockwise to "portrait"
3 Project the included images in /patterns, taking a picture of each
4 Resize the photos and replace the example images in /img with them
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step 1Theory: Triangulation
If you just want to make a scan and don't care how it works, skip to
Step 3! These first two steps are just some discussion of the technique.
Triangulation from Inherent Features
Most 3D scanning is based on triangulation (the exception being time-of-flight systems like Microsoft's "Natal "). Triangulation works on the basic trigonometric principle of taking three measurements of a triangle and using those to recover the remaining measurements.
If we take a picture of a small white ball from two perspectives, we will get two angle measurements (based on the position of the ball in the camera's images). If we also know the distance between the two cameras, we have two angles and a side. This allows us to calculate the distance to the white ball. This is how motion capture works (lots of reflective balls, lots of cameras). It is related to how humans see depth, and is used in disparity -based 3D scanning (for example, Point Grey's Bumblebee ).
Triangulation from Projected Features
Instead of using multiple image sensors, we can replace one with a laser pointer. If we know the angle of the laser pointer, that's one angle. The other comes from the camera again, except we're looking for a laser dot instead of a white ball. The distance between the laser and camera gives us the side, and from this we can calculate the distance to the laser dot.
But cameras aren't limited to one point at a time, we could scan a whole line. This is the foundation of systems like the DAVID 3D Scanner , which sweep a line laser across the scene.
Or, better yet, we could project a bunch of lines and track them all simultaneously. This is called structured light scanning.
Triangulation from Inherent Features
Most 3D scanning is based on triangulation (the exception being time-of-flight systems like Microsoft's "Natal "). Triangulation works on the basic trigonometric principle of taking three measurements of a triangle and using those to recover the remaining measurements.
If we take a picture of a small white ball from two perspectives, we will get two angle measurements (based on the position of the ball in the camera's images). If we also know the distance between the two cameras, we have two angles and a side. This allows us to calculate the distance to the white ball. This is how motion capture works (lots of reflective balls, lots of cameras). It is related to how humans see depth, and is used in disparity -based 3D scanning (for example, Point Grey's Bumblebee ).
Triangulation from Projected Features
Instead of using multiple image sensors, we can replace one with a laser pointer. If we know the angle of the laser pointer, that's one angle. The other comes from the camera again, except we're looking for a laser dot instead of a white ball. The distance between the laser and camera gives us the side, and from this we can calculate the distance to the laser dot.
But cameras aren't limited to one point at a time, we could scan a whole line. This is the foundation of systems like the DAVID 3D Scanner , which sweep a line laser across the scene.
Or, better yet, we could project a bunch of lines and track them all simultaneously. This is called structured light scanning.
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Forgot the image.
JAZ97
1 Getting a 3D model and using that for interaction.
2 Recording at a higher speed (e.g., 30 fps, 60 fps).
Even the best systems (like the Radiohead one) generally see these as exclusive, and don't do decoding at high framerates while capturing.
For 1, the trick is to have a fast camera like the PS3Eye that you can constantly get new frames from and approximately sync to the projector (the projector should not have a color wheel).
For 2, you just need a fast camera. I started with a PS3Eye, but recently have been using digital cameras like the Canon G10 and 7D for recording at 30 or 60 fps and decoding later.
The software for both of these cases is available on Google code . Case 1 is called "preview" and Case 2 is covered by "decode" and "capture".
If you have more questions/ideas, feel free to write to the structured light google group !
Try the demos for those libraries, and if they don't work email the library creators.
Use whichever orientation has the most depth variation. So if you have something that has vertical waves in it, use a horizontal pattern. The idea is that you want one line of the pattern to look "curved" from the camera's perspective.
However, i don't underesting how " capture-2.zip" works? Unzip it and then I click "capture.exe", it can find my webcam and also three kinds of patterns so on. But i don't know how to take picture, I click my webcam, it didn't work. Thx a lot.
You need a PS3Eye ideally, as it's designed to work with that camera. Anything else is probably too low of a framerate to work very well. Once you've captured the image sequence, load it into the decode app to play it.
More information is on the Google group .
Where can find the three phase scanning theory?
Thanks
I have a question. You say that "We're just projecting three frames, so you could use transparencies and an overhead projector, or even a slide projector, but you're best off with a digital projector you can feed with your computer.' Is there any difference or difficult when I use like slide projector?
Thanks for your help.