Mirror Image

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Google Googles, QR codes, localization

There are two recent developments related to Augmented Reality and Google – Google Goggles and Google integrating QR codes into Google Maps. While I was talking on twitter with @noazark the question arise about Google Google not doing real-time localization of the user, thus not being a “real” AR.
Here come QR codes. QR code are extremely easy to recognize in the camera image, and their square shape allow for fast calculation of camera position relatively to QR. In fact each QR code include three fiduciary markers:

And well known marker-tracking technique easily applied to them. Marker tracking could be augmented (pan intended:) by planar tracking of the corners of the pattern itself. That allow for attaching virtual 3d objects/animations to QR codes, but there is more in it. As QR code contain more than 4k of data, exact GPS coordinate, pattern orientation and its’ size could be encoded in the pattern. That way mobile phone seeing the code can easily calculate it’s exact 3d coordinate and orientation, not only relatively to QR, but absolute.
More of it – QR code can have coordinates of nearby QR codes, creating kind of localization grid, which can point user to any location covered by that grid with arrow on the screen of the phone.
Now to markerless tracking – QR code can be used to jump-start markerless tracker and assist it with error-correction(drift compensation), especially mentioned grid of the codes. That is especially relevant to markereless trackers which use planar structures and straight edges.
Now there is one problem here – white QR code is easy to segment out of dark background. But on white background it not so easy to recognize, and embedded fiduciary markers will not be seen form afar. Here is suggestion – make thick black frame around the QR, and make it part of the extended standard. This square shape would be easy to recognize, even if it’s only couple of dozen of pixel in diameter. With incremental tracking phone will be able to track it(after initial close up) even if moved quite far from the QR. If this square frame is part of the standard, always having the same relative size, it could be used for distance estimation.
Now combine it with Google Goggles real time and you have functional AR with 3d registration.

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9, December, 2009 - Posted by | Augmented Reality | , , , , ,

2 Comments

  1. Do you know the mathematical formula for calculating the size to distance ratio for QR codes?

    How big do they have to be for billboards I have seen in pictures from Japan etc.

    Angle?

    thanks!

    Comment by Jesse W. Poe | 2, February, 2010

  2. It depend on the camera resolution and focal length. My guess is the unit of the pattern (smallest square) should be at least 8-16 pixels on the screen, and you have to scan several frames for reliable decoding.

    Comment by mirror2image | 2, February, 2010


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