Microsoft Kinect SDK depth data to real world coordinates - kinect

Question

I'm using the Microsoft Kinect SDK to get the depth and color information from a Kinect and then convert that information into a point cloud. I need the depth information to be in real world coordinates with the centre of the camera as the origin.
I've seen a number of conversion functions but these are apparently for OpenNI and non-Microsoft drivers. I've read that the depth information coming from the Kinect is already in millimetres, and is contained in the 11bits... or something.
How do I convert this bit information into real world coordinates that I can use?
Thanks in advance!

Answer 1

This is catered for within the Kinect for Windows library using the Microsoft.Research.Kinect.Nui.SkeletonEngine class, and the following method:
public Vector DepthImageToSkeleton (
float depthX,
float depthY,
short depthValue
)
This method will map the depth image produced by the Kinect into one that is vector scalable, based on real world measurements.
From there (when I've created a mesh in the past), after enumerating the byte array in the bitmap created by the Kinect depth image, you create a new list of Vector points similar to the following:
var width = image.Image.Width;
var height = image.Image.Height;
var greyIndex = 0;
var points = new List<Vector>();
for (var y = 0; y < height; y++)
{
for (var x = 0; x < width; x++)
{
short depth;
switch (image.Type)
{
case ImageType.DepthAndPlayerIndex:
depth = (short)((image.Image.Bits[greyIndex] >> 3) | (image.Image.Bits[greyIndex + 1] << 5));
if (depth <= maximumDepth)
{
points.Add(nui.SkeletonEngine.DepthImageToSkeleton(((float)x / image.Image.Width), ((float)y / image.Image.Height), (short)(depth << 3)));
}
break;
case ImageType.Depth: // depth comes back mirrored
depth = (short)((image.Image.Bits[greyIndex] | image.Image.Bits[greyIndex + 1] << 8));
if (depth <= maximumDepth)
{
points.Add(nui.SkeletonEngine.DepthImageToSkeleton(((float)(width - x - 1) / image.Image.Width), ((float)y / image.Image.Height), (short)(depth << 3)));
}
break;
}
greyIndex += 2;
}
}
By doing so, the end result from this is a list of vectors stored in millimeters, and if you want centimeters multiply by 100 (etc.).