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Hardware for Homebrew Motion Capture?
goruka asks: "We are a small garage game development and 3D animation group, and as such, we try to develop by reducing costs as much as we can. Recently, it came to our mind that we could setup and develop a home-brew motion capture system by using three consumer USB web-cams to motion track bright objects attached to the body. However, we don't know which web-cam models can: capture at a decent frame rate (25fps) and resolution; are supported and easily programmed under GNU/Linux, since we'd like to later release our software as open source; and lastly, won't cost us a fortune. What are your experiences with such devices?"
Since you probably don't need to do anything real-time with the capture data, I'd suggest that you use whatever inexpensive cameras you can - and record streams onto video. Ideally, you'd borrow three camcorders and use them. Then you can at your leisure transfer the streams to a machine via firewire and calculate 3d-data to your hearts' content.
The benefit of this setup is that you can get away with very cheap hardware (you can probably borrow needed camcorders from friends and family if it's just a temporary deal), and the image quality - resolution, dynamic range, low-light performance, noise - will be a lot better than with a heavily compressed usb-cam stream.
As for synking the streams, you have that problem with three usb cams as well (can't caprture three usb-streams on the same computer), and with camcorders at least one step up from the bargain bin, you should be able to use sync cabling if you're really concerned about capturing frames at the same instant. I doubt that would be necessary, though, for the kind of precicion you're looking at getting (just do a linear interpolation between captured points to do an approximate soft sync should be fine for any movement you can hope to capture at 25/50 frames/s anyway).
Trust the Computer. The Computer is your friend.
This is a lot of work but also a lot of fun! I did it for a real-time demo project with a few friend. We used Christmas fairy lights and 5 mini-VHS camcorders. You can see the result at the very end of our Childbone demo.
Nowadays, using webcams will save you a lot of troubles, and you can find lots of very useful codes on the Internet (such as Intel's OpenCV, however majors issues that you still have to solve would be calibrating camera positions and reliably tracking crossing markers in images. In my system I had to do an editor to manually reassign markers when incorrectly detected or labeled, which can be a very tedious task...
I would recommend Logitech Quickcam Pro 5000 webcams, as they are USB 2.0, can do 640x480 at 30 fps, and most importantly use the somewhat recent generic USB Video Class spec, for which a driver for linux is available. I have a few of those and the image quality is quite good :)
Good luck!