Seek for quick registration method

[whu (whucsu)]

I tried it, and seemed that it worked, but still need some help.
In the slicer scene, a model loaded, EM tracker loaded, as below:

In the left view, LV simulator is the model;Locator_probetotracker is the “needle” model that can move freely ; the LinearTransform is added mannuly intened to receive the registration transform.
After using the Fiducial registration wizard module, “From” is the markup in the LV simulator; “To” using the transform as [quote=“lassoan, post:11, topic:24943”]“Place fiducials using transforms” section[/quote]
The result as below:

Here I meet some questions：
1）RMS Error maybe too high ? though for three point-pair …
2) How to change the

@lassoan

transform tree

as in the firt image, in order to fill with the expection as

@whu

As to the real application, I just want to make the EM tracker（on the physical model） registrated to the virtual Needle( on the CG model in Slicer)， like other IGT example below.

Let the needle follows the EM tracker.

Thanks for any advices.