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Messages - Hillfire

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...thanks for not linking to a shot from the Paris Hilton tape.

Anyway, the problem with a recognition/filter program is that the wiimote can only return 4 points that were detected and the approximate radius of those points. It does all the image analysis internally, through an unknown algorithm. That is not nearly enough data to determine what is being observed when there are possibly hundreds of points of reflection.

  - Ken

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Wiimote Desktop VR/Head Tracking / Re: Single camera vs 2 eyes
« on: January 25, 2008, 09:23:54 PM »
Figures that the shutter glasses ($110 for the full system) use an IR signal to sync with the refresh rate of the screen. This would create some tracking problems due to reflections and make use of a second wiimote for control impossible... they would need to be RF for this to work.

I would really like to play some COD4 with head-tracking and stereoscopic vision. That might be worth an extra $100.

  - Ken

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Wiimote Desktop VR/Head Tracking / Re: Improving to 6 DOF head tracking
« on: January 24, 2008, 09:14:19 PM »
Fixed temporal intervals is really where I was going with that rant, just to tired to convey it. The frequency calculation really is just how long the LED has to be off for both wiimotes to recognize it, to summarize, it would be .04 seconds or longer. HighDesert, kudos, you described this method much better than I did.

Geometric placement would really depend on the scenario. In all scenarios, you can leave exactly one of the LEDs solid without any ambiguity as long as all the others are identified. In the DesktopVR/sword example, you would only need to identify two of the LEDs, one on the sword and one on the head. The position of the second LED on the head can be guessed at. However, you may hold the sword tip (if the handle LED was identified) near/in front of your head, again making it ambiguous. As usual, some logic could get around this with relative accuracy, but that just adds calculation time.

Unfortunately, the "geometric LED curtain" doesn't work with the wiimote. The device is limited to exactly four points of detection. We should consider this lucky since Nintendo had no reason to detect any more than two.

This has certainly gotten of the topic of this thread.

  - Ken

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Wiimote Desktop VR/Head Tracking / Re: Improving to 6 DOF head tracking
« on: January 23, 2008, 11:17:10 PM »
It sounds like identifying the LEDs is the most promising way to go with this. You could even trick the wiimote into reading more than 4 points with this method.

If we were to assume the simplest scenario with two wii-motes and 4 LEDs, where each LED is uniquely identifiable and the distance/angle between the wii-motes is known, then 6 DOF is certainly possible. The math is fairly straight forward as has been discussed in this thread... or in most 3D graphics classes.

The issue is really just point identification. If we assume that the refresh rate of the CCD is 100Hz (which I sincerely hope it is), then Nyquist[1] says the freq of the LED chirp (50% DC) needs to be less than 50 Hz. Most remote-control IR diodes can handle 40 kHz[2], so no problem there. Some error will occur, but as long as the chirp frequencies are known, it can work. A simple micro mounted inside a sword (I really like that idea) or on the back of a glove[3] can handle this easily.

It gets more complicated when the sampling of each wiimote is not synchronized. Worst case, they are 90-degrees out of sync. Now, the maximum frequency that can be reliably read by both sensors is about 25 Hz.

The sword thing only sounds really interesting if you include DesktopVR into it. With the point IDs you could track both one's head and one's sword... that would be some seriously immersive (and ninja like) game play.

I will work up some test code and hardware for this once I get my Bluetooth receiver.

As an aside, being able to uniquely identify each point, even in a one wiimote scenario, will allow very complex interface gestures by providing unique paths for each point... but that's another forum.

[1] - http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem
[2] - http://scv.bu.edu/GC/shammi/ir/
[3] - http://www.sparkfun.com/commerce/product_info.php?products_id=8465

  - Ken

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