about Kinect coordinate transformation

[haohaoxuexi1]

I made a simple code to explain my problem

import viz
import vizshape

viz.go()
grid = vizshape.addGrid()
viz.MainView.setPosition(0,1,-5)

#now the sphere should be around 7 meters away from the main
s = vizshape.addSphere(radius=0.1)
s.setPosition([0,0,2])

I added a sphere to the scene and the scene is around 7 meters in front of the mainview.

I want to achieve that when the position of mainview moved, the sphere can move to the relative position (which is around 7 meters in front of the mainview) (defining a function to achieve it). And I also need to know the current global position of the sphere.

Hopefully, you can understand what I want to achieve. I think it is regarding coordinate transformation.