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Messages - Timo

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1
Project Ideas / Wiimote 6DOF tracking
« on: January 11, 2009, 01:46:57 PM »
Hi there,

I developed a 6DOF tracking for the wiimote a setup a vrtual reality system using two wiimotes and a stereo monitor. The software is developed with XNA. You can see my youtube video:

[youtube]http://www.youtube.com/watch?v=eLy9AWi67XU&feature=channel_page[/youtube]

For a yet to complete technical description please visit my homepage:
http://www.vrhome.de/technical-articles

Best regards,

Timo

2
I personally prefer the reflector method.
You have the following advantages:
- need no battery at tracked device (e.g. head)
- using bigger reflectors you get subpixel resolution (I don't know if this works with the wiimote)

I use reflector tape that you can get in stores (probably from scotch) - in Germany in buy it in "Obi Baumarkt". Then I put this on small wood balls and finished are my markers.
Then you need IR-light directly from the camera - the wiimote. It will not work, if you put the light somewhere else! Depending on the distance you work with you need the right amount of ir-leds. In electronic stores you might find prebuilt ir-lights, usually for night vision security application. But you can also build it yourself, but buy leds with a wide opening angle as most ir-lights are spotlights. In Germany you can get a nice little ring of ir-leds from "Conrad".

Using your eyes will not work, as they do not reflect enough. It is only used in very special eye-tracking systmes where the camera more or less only sees the eyes.

Cheers,

Timo

3
Wiimote Desktop VR/Head Tracking / Re: Improving to 6 DOF head tracking
« on: February 06, 2008, 12:56:45 PM »
Hi all,

I developed my own tracking system using OpenCV. DeMenthon's POSIT algorithm for 6DOF tracking is part of OpenCV. I tried and tweaked a lot arround with 6DOF tracking and still like POSIT best. Approaches that try to solve mathematic equations directly usually don't work well because of numerical stability.
Unfortunately for my tracking I need 5 points!!! I use a firewire DCAM industrial camera (you can get from 150,-$) and infrared light attached to the camera. On my devices I use reflective markers (usually balls). I can track up to 4 different devices without problem in full 6DOF with good quality. I also use the Kalman filter, that is implemented in OpenCV to reduce the jittering.

DeMenthon's algortithm also works for just 4 points, so it should be possible to use it with the wiimote.
The main difficulty is to relate the 2d points to the 3d-object points. For headtracking, where you can assume the head in a specific position this should be easy.
But DeMenthon also presented a paper SoftPOSIT, were the points do not need to be related. A C implementation of his algorithm is available on his homepage.

The question for me remaining is, how to get the intrinsic camera parameters and if the resolution of the of the wiimote is good enough to give resonable results.

So, does anybody know the wiimote cameras focal point, image point size, resolution and distortion parameters?

Cheers,

Timo

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