Question on the numerical values of depth data

[Joanie]

I have a question on the numerical values of depth data.
What does it represent exactly?

1) Distance from the IR Projector to point?

2) Distance from the IR Camera to point?

3) Distance from the IR Projector/Camera to the plane of the point?
(where the plane of the point is parallel to the Kinect's face, and
the line from Kinect to the plane is perpendicular)
E.g. if you place a flat piece of paper in front of Kinect, will the
depth values across the width of the paper be the same?

I hope someone understands what I'm trying to ask.
Thanks much.

[Eddie Cohen]

The correct answer is 3.

Eddie.

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[pixel]

So is there a limit to the range of the values?
for example on libfreenect, its said that the precision on the
depthmap is 11bits. giving us values from 0 to 2048.
How is that with openni ?

[Eddie Cohen]

OpenNI represents depth values as the distance from the camera plane to the object in millimeters. The pixel size is 16-bit, meaning it can represent any distance from 0 to ~32 meters.
The PrimeSense sensor produces values from ~30 cm to ~10 meters.