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CHAPTER 7: Point Clouds, Part 1 > Moving From Depth Map to Point Cloud

Moving From Depth Map to Point Cloud

The depth data obtained from the Kinect is in the form of a 2-D intensity image. There is clearly some correspondence between true depth (distance from the camera in meters) and the Kinect disparity units used in the depth image, but it might not be obvious how to convert one to the other. This is where the calibration data obtained previously becomes useful.

The conversion from disparity units to meters is done with the following formula:

z=1/(value*dc1 + dc2)

The conversion is determined by the coefficients dc1 and dc2, which control the scale and offset of the conversion respectively. Ideally, dc1 and dc2 should be calibrated as well, but this requires a different calibration procedure (see www.ee.oulu.fi/~dherrera/kinect/). For now, we will use dc=-0.0030711016 and dc2=3.3309495161. The value 2047 is a special case in the depth image; it indicates an unknown depth.


  

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