# Wiimote Project

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### Messages - dougnukem

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##### Wiimote Desktop VR/Head Tracking / Re: Improving to 6 DOF head tracking
« on: January 15, 2008, 11:04:08 AM »
Awesome idea! I think the 3 point and 4 point tracking on the wii is going to be difficult, mainly because we're not able to get a snapshot image of all four points at any given time. From what I can tell image data is sent in packets containing (x, y, radius) where it determines the x and y location and the approximate radius of the light being detected.

So to track 3/4 points we need a way to "know" that when a point moves to a new location where it moved from so we know that it's the same point. I don't have my wiimote yet so maybe I'm off base and maybe the wiimote libraries already help coordinate this information.

Also is there any reason why it says you need 4 points (not in the same plane) to track a 3D object.

http://idav.ucdavis.edu/~okreylos/ResDev/Wiimote/index.html
Quote
Projection of a custom IR beacon with four LEDs in a non-planar arrangement onto the Wiimote camera's image plane.

Is that for general 3D object tracking, not simply VR head tracking (There's less rotation in head tracking as you really can only move 180 degrees 90 in each direction).

I feel like the 3 point method would work fine for VR head tracking (it seems to work for the IR-Track software.

Has anyone worked out the intrinsic camera properties for the wii camera, so that we can accurately track a measured 3/4 point object. I think if someone sets up a test case (place a 3 point object at a set distance from the camera), then we can figure out the projection plane, frustrum geometry, and focal point position.

I think we the intrinsic wii camera properties that need to be calculated are (according to Oliver Kreylos):
• Pixel size - The width and height of each pixel on the camera's sensor in physical coordinate units, e.g., millimeters.
• Focal length - The orthogonal distance of the camera's focus point (center of its lens) from the image plane in physical coordinate units
• Center of projection - The position of the orthogonal projection of the camera's focus point onto its image plane in physical coordinate units. This 2D coordinate can be combined with the camera's focal length to express the focus point position as a 3D point.

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