General Wiimote and Technology > Project Ideas

Dual Wiimote 3DOF single IR source tracking

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inio:
How did you do the camera calibration?  Did you just solve for the extrinsic parameters, or also intrinsic, or even better, did you do a full photometric calibration of the cameras?  If you solved for any intrinsic parameters, how different did the two wii remotes end up?

nebulus:
Hi inio

Sorry you lost me there a bit with all your intrinsics and extrinsics!
Could you describe better what you mean?


I did very little in terms of calibration, the wiimotes were placed at 45degrees purely by eye, I did some measurements to work out the wiimote field of view which worked out to be almost exactly the same for the 3 wiimotes I have (41 HFOV x 31 VFOV), and used this in the calculation of the ray directions.

The distance between the wiimotes was roughly 30cm, but this is almost irrelevant as the sources positional information calculated in relation to the two wiimotes position.
As long as the wiimote position and directions were set relatively accurately, it works perfectly well.

I was very surprised by how well this very unscientific method worked!

I'm not sure how strict Johnny was with the maths in his original example application, I imagine he was more thorough than me, but in truth I doubt all the other instances where people have played with the demo have been as strict with getting the numbers correct.  I've never played with Johnny's demo so I could be mistaken about the need for configuring it with accurate measurements.

To be honest I had more issue with the noisy jittery signal that the IR cameras produced, which was more of an issue for me. 



inio:
Ah, I figured it was a pretty unscientific approach but you can always hope ;)*

From a Computer Vision perspective, cameras are defined as "Intrinsic parameters" (fov, optical axis, and skew), and "extrinsic parameters" (position and orientation).  For more accurate applications, you also compensate for lens distortions that can't be represented as fov, optical axis, and skew (typically represented as a polynomial function from the measured distance off the optical axis to the actual distance off the optical axis).

*my research requires very accurately calibrated wii remote cameras so I'm always hoping I'll find someone who's solved that problem for me.  I can't use traditional approaches because it isn't a "camera" and doesn't record images.

tarantula78:
'scuse me if this is a noob question but if one wiimote can track XYZ why do you need two wiimotes? isnt one enough to capture the depth, drop and height?

defray:
@ tarantula:
Wiimote cannot track light sources in 3D by infrared, only the other way round (position of the Wiimote via the sensor bar) or by using the acceleration sensors, but they are too sluggish for reliable und fast tracking.
In infrared the Wiimote essentially only sees a dot of light on an 2D-pane, but with two Wiimotes you get two different panes and you can easily calculate a 3D position.

Using this 3D tracking one could achieve some kind of virtual input (like on a keyboard) or other interactions ... is somebody working on something like that ? This could be used for all kinds of stuff you'd normally use a touchscreen (or even multitouch screen) for, e.g. an image viewer.
Would be nice to do something on my TV this way, comfortably from the sofa, with just an IR glove or two.

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