I find kinect depth fomula, Is it right? modified Question

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Hi. I find kinect depth fomulas.

But, I'm wondering how to know relationship of depth value using OpenNi?

In libfreenect, this formulas

1. float dist =100/(-0.0030711016*rawdisparity + 3.3309495161); //ros distance (cm)

2. float dist2 = 12.36 * tanf(rawdisparity/ 2842.5 + 1.1863); //Stéphane Magnenat distance (cm)

Can I use the fomulas in OpenNi?

At (http://www.ros.org/wiki/kinect_calibration/technical)

There is the depth fomula

z = b*f / (1/8 * (doff - kd))

Is the same true for the OpenNi driver?

Can you talk to me how to get the depth relation?

I'm using ubuntu and OpenNi driver.

I saw the disparity has 11-bit value.

So disparity range is 0-2047.

If it is true, any disparity makes the formula's denominator zero(0).

Then, the formula is infinity.

How did this happen?

Disparity 11bit, is it right??