Should the object tracking sample be using the depth camera when tracking objects in 2 and 3D? It seems to use the depth camera to create the maps but only uses the optical tracking for actual tracking?
Most of the optical tracking techniques rely on 2D images, so it wouldn't surprise me at all that they are using only 2D images. I guess they're using IR instead of RGB to be able to track in the dark though.
But, nothing is stopping you from tracking in 3D if for some reason it better suits your application.